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Notes: We analyze the theoretical basis of a procedure to determine an unknown normalization factor in discretized wave functions, which we have successfully used in a series of calculations of resonance widths for atomic and molecular systems. By reducing this determination to that of a suitable interpolation function for the energy eigenvalues, the problem is easily solved when atomic basis sets are chosen according to simple rules. Illustrations of our procedure are presented for atomic, molecular, and model systems; renormalized wave functions are compared with the exact ones for these model systems. The resulting method of renormalized continuum wave functions has a wide range of application in the study of long-lived quasibound states (predissociation, autoionization, photoionization, unimolecular reactions, etc.).

Notes: Transmission of vibrational excitation energy conserved in cis-conformation of retinal to the outlet proton channel is considered from the perspective of quantum theory. A distribution of vibrational excitations in the channel is found; it allowed to calculate the magnitude of the directed drift proton current. The differences between velocities of proton movement in active and passive channels are considered. A transition of retinal from cis- to all -trans- conformation with the subsequent capture of proton by Schiff base out of the inlet channel is described. The lack of proton in this channel, i.e., in the H-bonded chain, is eliminated at the expense of the capture of a proton out of the cytoplasmic water enviroment. The correspondence between theoretically established states and spectroscopically identified forms of bacteriorhodopsin (inter-mediates L, M, N, and O) is proposed.

Notes: The generating functional Z(N) of the molecular orbital theory of N electrons has been projected into a subspace of atomic orbitals. By application of the saddle-Point approximataions to the corresponding effective action, a set of equations of motion results. These equations are the classical Roothaan's equations of quantum chemistry.

Notes: The recently developed integral discretization technique for the generator coordinate method is applied to discuss some features of Gaussian expanded wave functions. Using the hydrogen atom ground state, it is shown that the nuclear cusp problem has an interesting relation with the generator coordinator weight function, which allows the production of accurate wave functions by an integration criterion.

Notes: The two-dimensional (2D) band structure of (polyphthalocyaninato)Ni(II), Ni(ppc), has been analyzed by a self-consistent field (SCF) Hartree-Fock (HF) crystal orbital (CO) formalism based on an INDO (intermediate neglect of differential overlap) type Hamiltonian. The calculated HF band gap of Ni(ppc) amounts to 0.24 eV. The highest filled band is a ringlike a1u combination (D4h symmetry label) localized at the carbon sites of the organic fragment. Remarkable hybridization in the valence band leads to the considerable band width Δ∊v of 2.92 eV. This value is close to the Δ∊v numbers which are conventionally encountered in one-dimensional metallomacrocycles. The effective width of the states in Ni(ppc) is 13.8 eV. In graphite a net π interval of 13.0 eV is predicted by the present CO formalism; i.e., the energetic distribution of the π electrons is roughly comparable in both 2D solids. The Ni 3d states in Ni(ppc) are far below the Fermi level which is calculated at -4.9 eV; they are predicted between -12.2 and -16.4 eV in the mean-field approximation. Quasi-particle corrections lead to a significant shift of these strongly metal-centered states. Important electronic structure properties of Ni(ppc) are compared with those of 1D metallomacrocycles with similar molecular stoichiometry. The total density of states distribution of Ni(ppc) has been fragmented into projected (ligand π and σ, Ni 3d) contributions in order to allow for a transparent interpretation of the 2D band structure.

Notes: Conformational preferences of the hypermodified nucleic acid bases N6-(Δ2-isopentenyl) adenine, (i6Ade) and its 2-methylthio derivative (ms2i6Ade) have been investigated theoretically by the quantum chemical perturbative configuration interaction using localized orbitals (PCILO) method.The predicted most stable conformation of i6Ade and ms2i6Ade are such that the isopentenyl substituent is oriented away from the imidazole moiety of the adenine ring. The atoms N(6), C(10), and C(11) remain coplanar with the adenine ring for both molecules. However, in contrast to the predicted cis orientation of the C(10)—C(11) bond with respect to the C(6)—N(6) bond in i6Ade, the trans orientation is favored for ms2i6Ade. The plane of the isopentenyl group is rotated by 120° from that of the purine base in i6Ade, whereas rotation by 60° is favored in ms2i6Ade. The favored orientation of the methylthio group with respect to the C(2)—N(3) bond is trans; however, the alternative cis arrangement is also quite probable. The conformational implications of the methylthiolation of the isopentenyladenine are brought out in the context of the considerably large range of accessible (β,γ) and χ orientations. The compatible roles of i6Ade and ms2i6Ade in tRNA are thus understood, besides their distinguishing features.

Notes: The theory of the Baker-Gammel approximants is applied to the spectral density function associated with the adjacency matrix. As a result, various upper and lower bounds to topological invariants are obtained in a systematic manner. In particular, the (N, M)-type lower bound to the total π-electron energy of benzenoid hydrocarbons is derived for the first time.

Notes: It is shown that the Coulson-Rushbrooke theorem for odd alternant hydrocarbons [15] can be generalized for some classes of nonclassical systems containing heteroatoms. The energy spectrum of such conjugated polymers containing heteroatomic groups, in particular a nitroxide group 〉N—O, is analogous to that studied [1-4] in homonuclear alternant nonclassical polymers, whose ground state is characterized by maximum spin multiplicity. Their band structure is characterized by a wide energy gap, in the middle of which there is a band of degenerate or nearly degenerate quantum states.The presence of a narrow band of degenerate quantum states, the Hund rule, and the alternant character of the polymers of this group determine the maximum multiplicity of their ground state and may give rise to the creation of magnetic order in such compounds, if interchain correlations occur. This is in line with the investigations in Refs. 1-11.

Notes: The quasi-relativistic CNDO/1 method for molecular orbital calculations has been extended to the INDO/1 version where all monocentric repulsion integrals are taken into account. This version has been applied to calculate molecular geometries of MXn-type molecules, with the central atom belonging to from the second to seventh period. Properties of hypothetical superheavy elements (Z = 110-117) have been predicted. Transition metal complexes of the MCl42--type (M = Ni, Pd, Pt, and ePt) have been investigated from the point of view of spin-state and configuration stability.

Notes: The effect of basis set contraction and elimination of primitive Gaussian orbitals on the He2 interaction energy components have been studied within the SCF counterpoise corrected approach supplemented by a dispersion term calculated within the variation-perturbation scheme. Despite elimination of almost half of the primitive Gaussian functions from the saturated sp basis set and complete contraction of the remaining ones, the components of interaction energy in He2 suffer a remarkably small loss of accuracy except for the short range charge transfer contribution.

Notes: We have recently developed a new classification of the amino acid side chains based on doublet acceptor energy levels (DALs). These energy levels, taken as the eigenvalue of the highest occupied molecular orbital in the radical anion, provide insight into the shape of the tunneling barrier in protein electron transfer. We have used this classification to characterize several transfer pathways in myoglobin. We present here a study of the effect of changes in geometry on the doublet acceptor levels. We find that, in general, this influence is rather small for reasonable changes in bond lengths and angles (e.g., those resulting from thermal fluctuations in the protein structure). However, we have found that for serine, threonine and water, changes in geometry that might take place as a result of fluctuations in hydrogen bond geometries lead to rather large changes in DAL. We investigate these correlations in some detail. The relation between protein fluctuations and changes in the shape of the electron tunneling barrier is discussed. Additionally, based on the energetics of changes in the OH bond distance, we discuss aspects of the relation between electron transfer and proton transfer.

Notes: This short communication outlines preliminary work aimed at understanding the recognition of sialylated oligosaccharides by influenza virus haemagglutinin. Initial efforts to model the complex have used the electrostatic interactions between atoms in the binding pocket and (2) as a means of constraining the conformational search in docking these two molecules. Some important features of the lowest energy structure are discussed.

Notes: Ab initio calculations reveal that a cation, in a position equidistant from the two H-bonding oxygen atoms of (HC(OH)O · H · OH2)+, acts to push the proton from HCOOH toward OH2 if the ion is located near the  - OH or C—H group of HCOOH. In contrast, rotation of the cation out of the HCOOH plane, while maintaining its position relative to the two H-bonding atoms, leads to a potential which is little different than that observed in the absence of an ion. These findings are readily explained on the basis of ion-induced internal polarization of the subunit to which the ion is closer. Replacement of OH2 by HCOOH suggests that polarization of the more distant subunit can also be a factor.

Notes: In this work the problem of normal vibrations of a molecule isolated in the argon gas and nitrogen gas matrix is considered. Modification of a valence force field to this problem is described, allowing the use of Lennard-Jones-type pair potentials for molecular-matrix and matrix-matrix interactions. For the selection of molecular-matrix pair potential parameters, the procedures based on combination rules are employed. To obtain the vibrational frequencies a monosubstitutional site in the crystal of an argon gas or a nitrogen gas is chosen as the most probable trapping site for the hydrogen cyanide molecule in the matrix of them. A pseudolattice method is applied to cubic 12 argon or nitrogen crystal fragments in order to eliminate the edge effect; we can obtain good results.

Notes: Since the introduction of dynamical simulated annealing (DSA) by Car and Parrinello in 1985, there has been growing interest in the use of nonlinear optimization to perform electronic structure calculations. We review here the complementary method of steepest descents (SD), a first-order treatment designed for local optimization. Modifications are discussed to adapt SD to a supercell treatment of metallic systems using a plane wave basis. An application to the Zintl phase compound NaTl is presented. The application of separable nonlocal pseudopotentials to improve this momentum space formalism is discussed.

Notes: Structural and energetic results are reported from a series of ab initio calculations on ground state CuCl2-4 in D2d and D4h conformations. All-electron Hartree-Fock calculations including geometry optimization have been carried out with large basis sets reaching triple-zeta valence plus f-function quality. Several ab initio effective core potentials and valence basis sets for Cu and Cl have been tested and evaluated based on comparisons of calculated results obtained at the Hartree-Fock or correlated (Moller-Plesset perturbation theory) levels with the all-electron and experimental data. The optimized structural parameters provided by all-electron or effective core potential methods are very similar, but they differ from averaged experimental data. Thus, the calculated CuCl bond lengths are typically 0.15-0.20 Å too large, and the ClCuCl bond angle (D2d) is 10-15° too small. The square planar (D4h) conformation represents a transition state and not a structural minimum for CuCl2-4. The energy difference between the two conformations (D4h - D2d) is consistently 16-18 kcal/mol at the Hartree-Fock level but approaches 10-12 kcal/mol at the highest levels of theory applied (UMP4(SDTQ)).

Notes: By calculations on CuCl2-4, CuBr2-4, and NiO10-6 clusters it is shown that a first-order configuration interaction (CI) calculation significantly improves the d-d and charge transfer (CT) spectra of ionic transition metal compounds. The first-order CI introduces delocalization (covalency) effects in the dn states, thus increasing the effective ligand-field splitting which is always underestimated at the Hartree-Fock (HF) level. It is demonstrated that this HF + first-order CI treatment is strongly related to a valence bond model. In this model the delocalization is introduced by explicit interactions with relaxed CT states. After account has been taken of the physically very different atomic correlation effects, a very good agreement with experimental d-d spectra is obtained, using only a small cluster. The effect of first-order CI on CT states is to account for hole localization and polarization effects which lead to reductions in the CT excitation energies in the order of 2-3 eV.

Notes: The known bounds on the eigenvalues of 2-Fermion reduced density matrices may be improved by considering unitarily invariant properties of the associated natural geminals and of the system 1-Fermion reduced density matrix. The polynomial invariants are particularly important, since they may be introduced systematically according to the degree of the polynomials.

Notes: We have extended the study of the description of local correlation effects provided by the different partitions of a configuration interaction (CI) wave function to the first excited state of the helium atom. Our analysis makes use of the local mean values of different moments of the interelectronic distance computed with the CI partitions as well as with Hartree-Fock and Hylleraas-type wave functions.

Notes: The resolution of a double determinant into a sum of spin-free orthogonal spin eigenfunctions is presented; its equivalent resolution of a spin function product θM0 is also given. Furthermore, a more general resolution of a Slater determinant into all spin eigenfunctions with S ≥ M is also obtained. Present work has also provided a method to calculate the linear coefficients in the expression of the primitive θMi in terms of the linear combination of spin eigenfunctions X̃NK (S, M).

Notes: An adiabatic formalism in the degenerate or quasidegenerate subspaces, which does not depend on the particular form of the switching function g(α, t), is outlined. A general factorization theorem for the dynamic operator Sα(t, t0 | g) is proved. This theorem enables one to formulate the perturbation expansion for the effective Hamiltonian and the wave operator which is free from the adiabatic divergencies.

Notes: A new definition of a canonical set of bonded functions has been introduced. For a given configuration with r singly occupied orbitals and given multiplicity, the set exhibits symmetry properties of a group of order r. It simplifies the evaluation of the energy matrix H as well as the orthogonalization procedure.

Notes: Recently, Perdew and Wang presented an expression for the exchange energy of a many-electron system. This functional has been adapted in the present work in variational density functional calculations of the total atomic binding energy of the Ne atom. For this atom similar calculations have been done earlier using the Dirac expression for the exchange energy. Three different total energy functionals have been considered: (1) the Thomas-Fermi-Perdew-Wang functional, (2) the above functional augmented by (1/9) of the original Weizsäcker correction to the Thomas-Fermi kinetic energy, and (3) the same functional as in 1 augmented by (1/5.3) of the original Weizsäcker correction to the Thomas-Fermi kinetic energy. The electron (number) density of the Ne atom has been constructed from hydrogen-like one-electron wave functions containing three variational parameters. Each of three total energy functionals have been minimized with respect to these parameters. Comparison of the Perdew-Wang and Dirac exchange energies shows that, in each of the three model pairs, the Perdew-Wang exchange energy is larger in magnitude than the Dirac exchange energy. It is also found that the exchange energy obtained by 2, -12.31 a.u., is in excellent agreement with the value of -12.22 a.u. calculated by Perdew and Wang with the Clementi and Roetti near-Hartree-Fock density.

Notes: The distribution of energy levels of an N-identical-particle system among the irreducible representations of the permutation group is examined for a “spin-free” problem. There are calculated the sums of powers of the eigenenergies obtained from the original N!-fold degenerate energy level when the interaction between the particles is switched on. The first-order perturbation theory is applied. Some results of the present approach are shown to be equivalent to the results of the Weyl's theory of the permutation group. The distribution of energy levels is found to be symmetric with respect to the average energy level belonging to a self-conjugate representation. For a special case of the Coulomb interaction the wave function of the highest level is fully symmetric, whereas that of the lowest level is fully antisymmetric with respect to the interchange of the coordinates of any two particles. The average energy and the dispersion of the levels belonging to a given representation are calculated for some N.

Notes: It is shown how the properties of the one-particle Green's function lead naturally to the definition of the so-called natural energy orbitals. These orbitals allow the fully correlated total energy of a system to be written in Hartree-Fock-like fashion and might therefore provide a bridge between sophisticated correlated wave functions and approximate theories of chemical structure and reactivity based on a Hartree-Fock-like energy expression. Moreover these orbitals form the basis for a self-consistent scheme to calculate the one-particle Green's function. The relation between these natural energy orbitals and the extended Koopmans' theorem is considered. Finally it is shown that the exactness of the lowest extended Koopmans' ionization potential implies the linear independence of the corresponding Dyson orbital from all other Dyson orbitals.

Notes: The shape wave u(r) is defined in such a way that the square of its absolute value gives the shape of the electron charge density for a nonrelativistic many-electron system: |u(r)|2 = ρ(r)/∫ρ(r) dr, where ρ(r) is the total electron charge density. The u(r) is treated as the probability amplitude for the shape of the electron charge density in the real three-dimensional space. The secular equation of the u(r) is given as L(r)u(r) = λu(r), where L(r) and λ are a real Hermitean operator and the eigenvalue, respectively. This equation has the form of the spinless one-particle Schrödinger equation. The potential is local and is a functional of ρ(r), and so we need a self-consistent field procedure to solve it. For equilibrium state shape wave u = ueq, which is temperature-dependent, and for stationary state shape wave u = u0, respectively, Leq(r)ueq(r) = λequeq(r) and L0(r)u0(r) = λ0u0(r). For one-electron systems, the latter equation reduces to the Schrödinger equation for a stationary state, with the usual eigenvalue λ0 = E0. In general, λ is identified with the Gibbs chemical potential μG. Boundary conditions such as the cusp condition at a nucleus and exponential decay at an infinitely large distance from the nucleus are easily implemented. In case L(r) allows complex eigenfunctions, u(r) = A(r)eiS(r), the hydrodynamical potential appears in the secular equation for the real amplitude A(r). The real phase S(r) satisfies the equation of continuity. By introducing «apparatus» operators [16], the excited state shape wave is also obtained. Comparisons are made with a recent discussion of Levy, Perdew, and Sahni [3].

Notes: The role of the boundary conditions is emphasized in determining the relation between the counting problem, posed by Coulson and solved by the number theorists, and the physical problem from which it arises. The surface energy term, which Coulson sought, does exist, but only when the periodic boundary conditions, which he used, are replaced by the finite box conditions.

Notes: The graph theory of molecular orbitals including second neighbor interactions (η) is considered here. Graphical methods of getting the characteristic polynomial for the π system of a conjugated molecule are given. It is shown that the characteristic polynomial can be factorized if there are symmetries in the molecule.

Notes: Calculations have been made at the minima of the X1A1 ground state of the ozone molecule. The equilibrium geometries have been obtained by means of CID calculations. The criterion adopted for the choice of configurations gives realistic results. CIPSI calculations at the two minima lead to an estimated gap of 0.92 eV between them.Our results agree with the analysis of previous theoretical works on the relative stability of open and cyclic zone structures, showing that the D3h minimum is stable relative to the ground state dissociation limit.

Notes: The ground state energies of finite Hubbard molecules are calculated by numerically solving the Lieb-Wu equations for a complex Hubbard repulsion parameter U. From the positions of the singular points located in the complex plane, the radii of convergence of the perturbation expansions for the ground state energies are determined.

Notes: A simple procedure has been created for indexing the spin-free configurations of an N-electron system in spin state S. This indexing has been linked to a procedure for generating the matrix representations of the generators of the unitary group U(n) to enable a direct configuration study to be undertaken.

Notes: A perturbation expansion which connects the hydrogenic limit energy density functional to the Thomas-Fermi functional is discussed. This perturbation series, where the Coulomb energy density functional is treated as the perturbation to the hydrogenic limit functional, is, in fact, the q = (N/Z) expansion of Thomas-Fermi theory. A truncated form of the first-order correction to the functional provides further insight into the model which treats the ground state energy as a local functional of the electron density.

Notes: A size-extensive, multireferences coupled-cluster method for studies of quasidegenerate states based on the Jeziorski-Monkhorst [16] ansatz for the cluster operator (Ω = ∑eTjPj, where the sum is extended over the configurations spanning the model space), is presented and applied in pilot calculations. The method is referred to as multireference coupled electron-pair method (MR CEPM), because it is assumed that the individual cluster operators can be approximated by their two-body parts, i.e., Tj ≈ Tj(2). The linear version of this method (MR L-CEPM) is also discussed. Both methods are applied to two simple model systems: (1) a minimum basis set model involving eight hydrogen atoms in various spacial arrangements for which the degree of quasidegeneracy can be continuously varied; (2) a model involving the C2ν insertion of Be into H2. For the first time in multireference coupled-cluster calculations, the nonlinear parts of the equations are completely accounted for. The MR CEPM results are very encouraging for strongly quasidegenerate states. The MR L-CEPM results are slightly below the accurate (FCI) values.

Notes: The interaction of a carbonyl group with two adjacent aromatic units is discussed. The outer valence electronic structure of compounds of general formula Ph—CO—Ar, where Ar is phenyl, substituted phenyl, furyl and thienyl, is determined from their gas phase photoelectron spectra. Particular attention is paid to biologically active derivatives of 2-amino-5-chlorobenzophenone.

Notes: Proteins and other macromolecules may be viewed as shape-based (or tactile) pattern recognizers. Biological cells exploit this inherent capability by transducing macroscopic signal patterns impinging on the external membrane to microscopic patterns at the molecular level, via second messengers. The parallelism inherent in the wave function description of these microscale processes in effect serves to increase the computing power of molecular computing systems as compared to macroscopic analogs. The conversion and recognition process is highly reminiscent of measurement. The linking role of second messengers allows macroscopic signals to set the state of the cell (in analogy to state preparation), while enzymatic readout and control of cellular behavior is an amplification process that corresponds to measurement of the microstate at a later point of time. Since the standard time evolution equations are reversible and unitary, while measurement is not, it is conceivable that the study of molecular computing will lead to new insights into the relation between the microworld and the macroworld. The model presented suggests that projection processes that are masked in ordinary laboratory systems are brought to macroscopic significance by the highly nonlinear chain of amplification events in the biological cell.

Notes: We have developed a new algorithm which uses the trajectories of a discrete dynamical system to sample the domain of an objective function in search of global minima. We demonstrate the effectiveness of this algorithm by applying it to a model geometry optimization problem. Significant improvements in optimization efficiency are demonstrated, in that our algorithm returns lower minima than conventional line minimization in 79% of the optimization runs we made. The method is orders of magnitude less computationally intensive than simulated annealing, while returning good minima for functions possessing many local minima. The method is simple to program, and requires only two-point gradient calculations for its implementation.

Notes: Toward the goal of efficiently computing field lines for molecular vector fields, where each field-point calculation is computationally intensive, a few appropriate algorithms for calculating vector field lines are presented and compared for various representative applications. Among these algorithms are the first-order tangent-line method (TL), the fourth-order Runge-Kutta method (RK4), the infinite-order Bulirsch-Stoer method (BS), the second-order Taylor's series method (TS2), and the second-order “curvature-following” method (CF). The TL and the RK4 are well known. The TS2 and the CF are new. The RK4, The TS2, and the CF are appropriate for obtaining high accuracy with few field-point calculations. The TL is definitely not appropriate for this purpose, and the BS is so appropriate only at the highest level of required accuracy. The CF uses the value of the vector field and its gradient at the given field point in order to locate the center of curvature of the field line at that point and, thereby, to extrapolate the field line, as an arc of a circle, to the next field point. The TS2 uses the same information, but extrapolates the field line as a segment of a parabola whose vertex is at the field point. The BS is an infinite-order extrapolation on successively finer scale iterations of the lowest-order Runge-Kutta method. All of these methods are compared for the velocity field of a rotating disk, for the vector field of a point dipole, and for electric field of a high-speed orbiting charged particle. For all of these fields, the field lines are exactly expressible in analytic form, so the absolute errors of these different algorithms can be appraised. As several of these methods allow a rather large step size, it was found appropriate to use a continuous-(geometrical)-curvature interpolation scheme to interpolate between the field points on the generated field lines. One prefers this scheme to the use of cubic splines when the physical fields should have their “geometrical pictures” (even under approximation) invariant to an arbitrary change of the coordinate system used in the calculation. These methods have also been used to generate field lines for the approximate and the exact fields of a half-wave antenna. In this case, one sees very large differences in the structure of the field lines of the approximate and the exact fields, in the near-field region, and also sees the manner in which each of these differences diminishes to zero as the field point approaches the far-field region; features that would have been very hard to observe by purely analytical methods. It is hoped that these methods for field line generation might have application for the field lines of the gradient of the molecular density (as in Bader's theory of atoms in molecules) and for the field lines of the electric fields of nucleic acid molecules.

Notes: The results of applying the simulated annealing method to find the lowest energy structure of the decane molecule are analyzed. The algorithm is found to be both efficient and economical. Some preliminary results are presented for a molecule of biochemical interest, Met-enkephalin.

Notes: Recently we derived, implemented, tested, and used successfully a new computational strategy for ab-initio MRD-CI (multireference double excitation - configuration interaction) calculations for molecular decompositions of large molecules and intermolecular reactions of large systems. We carry out the ab-initio SCF for the entire system, then transform the canonical delocalized molecular orbitals to localized orbitals and include explicitly in the MRD-CI only the localized occupied and virtual orbitals in the region of interest, folding the remainder of the occupied localized orbitals into an “effective” CI Hamiltonian. The advantage is that the transformations from integrals over atomic orbitals to integrals over molecular orbitals (the computer time-, computer core-, and external storage- consuming part of the CI calculations) only have to be carried out for the localized orbitals included explicitly in the MRD-CI calculations. The challenge arose to extend our MRD-CI technique based on localized/local orbitals and “effective” CI Hamiltonian to the breaking of a chemical bond in a molecule in a crystal (or other solid environment). This past year we have derived, implemented, and used successfully a procedure for doing this. Our technique involves solving a quantum chemical ab-initio SCF explicitly for a system of a reference molecule surrounded by a number of other molecules in the multipole environment of yet more further out surrounding molecules. The resulting canonical molecular orbitals are then localized and the localized occupied and virtual orbitals in the region of interest are included explicitly in the MRD-CI with the remainder of the occupied localized orbitals being folded into an “effective” CI Hamiltonian. The MRD-CI calculations are then carried out for breaking a bond in the reference molecule. This method is completely general. The space treated explicitly quantum chemically and the surrounding space can have defects, deformations, dislocations, impurities, dopants, edges, and surfaces, boundaries, etc. We have applied this procedure successfully to the H3C - NO2 bond dissociation of nitromethane with extensive testing of the number of molecules that have to be included explicitly in the SCF and how many further out molecules have to be represented by multipoles. To check the goodness of the model cluster approximation for crystalline nitromethane, we carried out ab-initio crystal orbital (XTLORB) calculations using our POLY-CRYST program. The difference in the XTLORB total energies between the 4 nitromethane molecules/unit cell and the 3 nitromethane molecules/unit cell (Table VIII), ER = E4 - E3 = -48.0609079 a.u., corresponds very closely to the reduced energy per nitromethane molecule, ER = (-;48.0605)9 a.u., calculated from explicit SCF calculations on the model nitromethane cluster in the multipole field of farther out nitromethane molecules for the model cluster. Thus, the multipole approximation for describing the effect of further out molecules on the SCF cluster energies is quite good.

Notes: The electrostatic interaction is a critical component of intermolecular interactions in biological processes. Rapid methods for the computation and characterization of the molecular electrostatic potential (MEP) that segment the molecular charge distribution and replace this continuous function by a series of multipole moments for each segment have been described. There are two sources of error in these techniques: 1( The truncation of the expansion after just a few terms, and 2) the charge in the segmental distribution that is more distant from the expansion center than the observation point. The first may be eliminated by finite expansion methods where truncation is unnecessary or performed in a manner that gives errors that are acceptably small. The second is inherent in the multipole expansion and results from the assumption in performing the expansion that the distance to the observation point is larger than the distance to all points inside the charge distribution. As the basis functions used in molecular wave functions have infinite extent, this will never be the case and the multipole expansion is never strictly valid. In practice this inherent error limits the range of usefulness of all multipole expansion techniques. To expand this range we have introduced a method that uses exact techniques to compute the MEP for the part of the molecular charge distribution described by the gaussians on each atom with the smallest exponential parameter and uses segmental multipole methods for the remainder of the charge. Using pyrrole with an STO-3G wave function as an example, this method significantly improves the potential in the range 1.4-2.0 Å from atoms with only a small increase in computational effort. If other basis sets are used with more diffuse gaussians the convergence of the multipole expansion will be at greater distances from the atoms and this type of correction will be more important.

Notes: Finiteness is usually imposed as a condition for physical admissibility of a wave function. Examination of this condition in both position- and momentum-space shows that finiteness of the wave function at the origin in one space implies “linear” integrability in the reciprocal space, except in some pathological cases. Some implications of this result are discussed.

Notes: The ground state energetics and equilibrium geometries of neutral and positively and negatively charged clusters of Li3, Li2H, Li2Na, Li2Mg, and Na2Li have been obtained from a self-consistent field-linear combination of atomic orbitals-molecular orbital calculations within the Hartree-Fock approximation. The correlation energies are included perturbatively using the Möller-Plesset scheme up to the fourth order. The geometries of all negatively charged clusters are found to be linear with bond lengths that are, in general, larger than their neutral or cationic counterparts. The adiabatic electron affinities and ionization potentials are calculated and compared with earlier theoretical results. The addition of an electron to the neutral cluster is found to stabilize the cluster further against dissociation. The spatial distribution of the electrons in these clusters is studied to determine the extent to which electrons added or taken out are localized in the clusters. Mulliken population analysis is also used to elaborate the charge state of the anionic and cationic clusters.

Notes: A simple proof is given for the thermodynamic inequality F - F0 - 〈H - H0〉0 〈 0 in the case when the two Hamiltonians H and H0 do not commute.

Notes: Electron correlation energies are calculated for a series of small molecules by fourth-order Møller-Plesset perturbation theory (MP4) and by quadratic configuration interaction methods. A method is suggested for partitioning the correlation contributions beyond fourth order that result from single, double, and triple substitutions. Detailed comparison of the results reveals that termination of the MP perturbation series at fourth order is inadequate for some electron-deficient species (inadequate treatment of double substitutions), for triply-bonded molecules (overestimation of the triples effect), and for some unsaturated radicals (poor treatment of single substitutions).

Notes: Die Reaktion von (η4-Butadien)bis(η-tert-butylcyclopentadienyl)-zirconium (95:5-s-cis-/s-trans-5-Gleichgewichtsgemisch) mit Hexacarbonylwolfram liefert den Zirconiooxycarbencomplex (6), der in der Raumgruppe P1 kristallisiert (Röntgenstrukturanalyse). Aufgrund des chiralen zentralen metallacyclischen Ringsystems und der chiralen Vorzugskonformation des Cp-substituierten gewinkelten Metallocensystems werden diastereoisomere Zirconiooxycarbenkomplexen 6 und 6′ gebildet. Röntgenstrukturanalyse und 13C-CP/MAS-Spektrum deuten auf das Vorliegen eines 80:20-Gemisches dieser diastereomeren Carbenkomplexe im Festkörper hin. Die temperaturabhängigen NMR-Spektren des Carbenkomplexes in Lösung werden mit einem Gleichgewicht der Diastereomeren interpretiert.

Notes: Die Addition von AHal2 an das Iminoboran iPr2NBNtBu (1a) ergibt die Diaminoborane iPr2NB(Hal)N(tBu)—AHal (2a-i) und das Triaminoboran (iPr2N)2BN(tBu)—AsBr2 (2j); der Austausch von Hal in 2e, f, j gegen NiPr2 bzw. Me führt zu den Produkten 2k-m. Durch Enthalogenierung von 2a, c, d, m mit Alkalimetall gelangt man zu den Dreiringverbindungen [—B(NiPr2)N(tBu)-;A-] mit A = B(NiPr2) (3), SiR2 (4a, b), P(NiPr2) (5), während sich mit Li2EPh (E = P, As) aus 2a,c Vierringverbindungen des Typs [—B(NiPr2)N(tBu)—A—E(Ph)—] mit A = B(NiPr2) (6, 7), SiMe2 (8, 9) bilden. Addiert man ACl2 an das Iminoboran Me3Si(tBu)NBNtBu (1b), so entstehen entweder die Diaminoborane Me3Si(tBu)NBN(tBu)—ACl (2n-w) oder unter Abspaltung von Me3SiCl die Vierring verbindungen [—N(tBu)B(Cl)N(tBu)—A—] mit A = GeMe2 (12), PX (13a-e), AsCl (14a). Denselben Typ von Vierringverbindungen mit A = BX (10a-d), SiX2 (11a, b) erhält man neben Me3SiCl bei der Einwirkung von Chloroform auf 2n-s. Durch Austausch des an das B-, P- oder As-Atom in jenen Vierringen gebundenen Cl-Rests gegen Alkyl-, Amino- und Alkoxygruppen kommt man zu den Derivaten 10e, f, 13f-h, 14b-j. Die Konfiguration aller Produkte in Lösung wird anhand der NMR-Spektren und die Struktur von 3, 6, 7, 12, 14b in festem Zustand anhand röntgenographischer Untersuchungen diskutiert.

Notes: Durch Umsetzung von ICo(CO)2(PR3)2 (1, 2) [R = Ph (1), Cy (2)] mit den sekundären Phosphansulfiden R23HP = S erhält man in Gegenwart von Et(iPr)2N die η2-Thiophosphinito-Komplexe (OC)2(R2R21P)Co(η2-PR23S) (3a,b,d,e,i,j,k,m,n). Die Me2PS und Et2PS-Verbindungen 3a,b,d oligomerisieren leicht unter Bildung von [(OC)2(R2R21P)Co(μ-PR23S]n (4a,b,d) (n 〉 2). Beim Austausch von PR21R2 (R1 = R2 = Ph) in 3a,d,j,m durch PPh2-Me, PPhMe2 und PMe3 entstehen neben den η2-Thiophosphinito-Komplexen 3f,g,l die dimeren Spezies [(OC)2(R21P) Co(μ-PR23S)]2 (5c,f,g,h,o). Die Dimerisierungstendenz hängt von dem sterischen Anspruch der Substituenten R1, R2 und R3 ab. Die Substituenten R1 und R2 in 5f,g sind für energetisch bevorzugte Rotamere verantwortlich, die sich in den 31P{1H}-NMR-Spektren zu erkennen geben. Die Rotationsbarriere berechnet sich zu ΔG≠ = 42 kj/mol. Nach Röntgenstrukturanalysen kristallisieren (OC)2(Cy3P)Co(η2-PEt2S) (3e), [(OC)2(Me3P)Co(μ-PMe2S)]2 (5c) und [(OC)2(Ph2MeP)Co(μ-PEt2S)]2 (5f) in der Raumgruppe P21/c, P1 bzw. P21/c mit Z = 4, 2 bzw. 2.

Notes: (CO)2(MeC5H4)Mn=C(OEt)Ph (1) reagiert stufenweise mit zwei äquivalenten Isocyanid R—NC 2 (R = a: c-C6H11, b: Me, c: Ph). In der ersten Stufe entstehen Keteniminkomplexe 3, die isoliert und spektroskopisch charakterisiert wurden. Sie bilden mit Isocyaniden  -  abhängig von deren Raumbedarf  -  unterschiedliche Produkte. 3a addiert sperriges 2a am Metall unter Verdrängung von N-Cyclohexylketenimin 7. 3b,c hingegen addieren 2b,c am Keteniminliganden zu isomeren 4- und 3-Imino-2-azetidinyliden-Komplexen 4 bzw. 5. Markierungsexperimente durch stufenweisen Einbau zweier unterschiedlicher Isocyanide ergaben, daß 4 durch [3 + 1]-Cycloaddition von 2 and 3 auf der vom Metall abgewandten Seite, 5 durch [2 + 2]-Cycloaddition auf der Metallseite entsteht. Mit steigender Reaktionstemperatur verschiebt sich das Konkurrenzverhältnis 4:5 zugunsten von 5. 4 und 5 lassen sich mit KMnO4 im Zweiphasensystem Ether/Wasser glatt in 4-Imino- 9 bzw. 3-Imino-2-azetidinone 10 umwandeln.

Notes: Die Alkali-triazaphosphininolate 2, 3, 4 und 6 werden durch Reaktion von 2,2-Difluor- bzw. 2,2-Dichlor-4,6-bis(trifluormethyl)-1,3,5,2λ5-triazaphosphinin (1 bzw. 5) mit NaOCHMe2, NaOCMe3, KOCHMe2 oder KOCMe3 sowie mit LiOSiMe3 erhalten. NaOSiMe2CMe3 reagiert mit 1 im molaren Verhältnis 1:1 bzw. 2:1 zu den Siloxyverbindungen 8 und 9. Das 2-Fluor-triazaphosphinin-2-ol 7 entsteht aus 4 und HF. 7 kann mit KOH in 2 übergeführt werden. Natrium-triazaphosphininolat 3 reagiert mit ClSiMe3 zum Siloxy-triazaphospininolat 10. Die N-Lithio-triazaphosphinin-2-amine 13 und 14 entstehen aus den aminofunktionellen Verbindungen 11 und 12 mit LiN(SiMe3)2. 14 reagiert mit ClSiMe3 zu LiCl und 15.

Notes: Die diamagnetischen Vinylnickel-Verbindungen trans-Ni-(CR1=CR2R3)Cl(PMe3)2 (1a: R1 = R2 = C6H5, R3 = CH3; 2a: R1 = C6H5, R2 = R3 = CH3; 3a: R1 = R2 = CH3, R3 = C6H5; 4a: R1 = R2 = R3 = C6H5) und Ni(CR1=CR2R3)(acac)(PMe3) (5: R1 = R2 = C6H5, R3 = CH3) bilden sich durch Einschiebung von Diphenylethin und 1-Phenylpropin in Methyl- oder Phenyl-nickel-Einheiten als Z-Isomere, die thermisch mit ihren E-Isomeren ins Gleichgewicht gebracht werden. 1-Phenylethin und 1-Phenylpropin ergeben selektiv (1-Phenylvinyl)nickel-Verbindungen. Austausch von Halogen liefert die Bromide 1b, 2b, 4b, die Iodide 1c, 2c, 4c und ein Cyanid 1d. Einwirken von LiR (R = Me, C≡CCMe3) auf 1a mit anschließender reduktiver Eliminierung ergibt Olefin RR1C=CR2R3, während Mineralsäuren oder Iod die Ni—C-Bindungen von 1a spalten und die entsprechenden Olefine (R = H, I) erzeugen. Eine ergiebige Synthese von Chloro(phenyl)bis(trimethylphosphan)nickel wird ebenfalls beschrieben.

Notes: Die Disproportionierung von 1,4-Cyclohexadien an kolloidalem Nickel läuft als mehrstufige Reaktion ab, bei der die Dehydrierung cis-selektiv erfolgt. Der Wasserstoff verliert vor der Addition seine molekulare Identität, so daß eine direkte H-Übertragung zwischen den Molekülen2) ausgeschlossen ist.

Notes: Ausgehend von (3R,4R)-3,4-Bis(diphenylphosphino)pyrrolidin (1a), bzw. dem N-Benzyl-Derivat 1b wurden [P(R,S),3R,4R,P′-(R,S)]-3,4-Bis(phenylphosphino)pyrrolidin (2a-*) und dessen N-Benzyl-Derivat 2b-* als Diastereomerengemische hergestellt. Aus 2a-* wurde isomerenreines (PR,3R,4R,P′S)-3,4-Bis(benzylphenyl-phosphino)pyrrolidin (3a-3) dargestellt. [P(R,S), 3R,4R, P′(R,S)]-3,4-Bis(methylphenylphosphino)pyrrolidin (4a-*) wurde aus 2a-* als Diastereomerengemisch erhalten, dessen Auftrennung über die Palladiumkomplexe der N-tert-Butoxycarbonyl-Derivate 8c-* gelang. [(PS, 3R4R,P′S)-1-(tert-Butoxycarbonyl)-3,4-bis(methylphenylphosphino) pyrrolidin-P,P′]diiodopalladium(II) (8c-1) und zum Vergleich [(3R,4R)-1-Benzyl-3,4-bis(diphenylphosphino)pyrrolidin-P,P′] (1,5-cyclooctadien)rhodium(I)-tetrafluoroborat (11) wurden durch Röntgenstrukturanalyse charakterisiert.

Notes: Die Synthese der Titelverbindungen vom Typ 5 und 10 sowie ihre intramolekularen Cycloadditionen zu den Produkten 4 bzw. 12 werden beschrieben.

Notes: Durch Claisen-Umlagerung der Acrylsäureester 7 und 21 wird die Konfiguration der Cyclohexenole trans-2 und trans-17 auf die Aldehyde 11 und 23 übertragen. Robinson-Anellierung führt von dort zu den Titelverbindungen 15a und 27a. Die Aufbaufolge ist über 14a, b iterativ angelegt. Zwei Ester des all-trans-Tercyclohexylalkohols 27a mit breiten smektischen Phasenbereichen werden beschrieben.

Notes: Die Synthese von Perylenfarbstoffen 2 mit terminalen Alkylgruppen wird beschrieben. Langkettige n-Alkylgruppen führen nicht zu einer Erhöhung der Löslichkeit, sondern zu einer Erniedrigung. Cycloalkyl-Reste bewirken ein Minimum an Löslichkeit im Bereich der mittleren Ringe und ein Maximum beim Cyclotetradecyl-Rest (2p). Starke Löslichkeitserhöhungen bewirken sekundäre Alkylreste mit zwei langen Ketten. Von diesen ist der Farbstoff 2v mit zwei 1-Hexylheptyl-Resten mit einer Löslichkeit von über 100 g/l in den meisten Lösungsmitteln, einer Fluoreszenzquantenausbeute von ca. 100% und einer ausgesprochen hohen Lichtechtheit auch für Spezialanwendungen geeignet.

Notes: (Phthalocyaninato)cobaltdichlorid, PcCoCl2, reagiert mit den Stickstoffbasen L = Pyridin (py), Pyrazin (pyz), 2-Methylpyrazin (mepyz) und 4,4′-Bipyridin (bpy) nicht zu Phthalocyaninato-Komplexen [PcCoL2]+ Cl- (1, X = Cl) mit Co3+ als Zentralatom. Es entstehen ausschließlich die gemischten Komplexe PcCo(L)Cl (3, X = Cl), die durch ihre IR-, FIR- und UV/VIS-Spektren und durch Thermogravimetrie (TG/DTA) charakterisiert werden.

Notes: Chloro(phthalocyaninato)rhodium, PcRhCl, reagiert mit den Stickstoffbasen L [L = Pyridin (py), 4,4′-Bipyridin (bpy), 2-Methylpyrazin (mepyz) und 1,4-Diazabicyclo[2.2.2]octan (dabco)] sowie mit L = Cyclohexylisocyanid (c-hxNC) zu den gemischten Komplexen PcRh(L)Cl, die durch ihre IR-, FIR- und UV/VIS-Spektren und durch Thermogravimetrie (TG/DTA) charakterisiert werden.

Notes: The facile activation of cis- and trans-1,2-diphenylbenzocyclobutene (DBC) either by charge-transfer irradiation of the electron donor-acceptor complex with tetracyanoethylene or by chloranil photosensitization leads to a series of rapid [4 + 2] cycloadditions. The role of the cation radical DBC+. as the reactive intermediate which undergoes a stereospecific, conrotatory cycloreversion is delineated, especially with regard to “contact” and “solvent-separated” ion pairs. Such cycloadditions induced by electron transfer are discussed in the context of the thermal valence tautomerization of DBC previously established by Huisgen, Quinkert, and co-workers.

Notes: Der Chelatring von Platin(II)- und Palladium(II)-glycinat, cis-, trans-M(NH2CH2COO)2 (M = Pt, Pd), läßt sich mit Trialkylchlorsilanen unter Bildung der Dichlorobis(glycin-silylester)-Komplexe, cis-, trans-MCl2(NH2CH2CO2SiR3)2 (1), öffnen. Aus 1 oder den Komplexen MCl2(NH2CHRCO2H)2 werden mit Oxalylchlorid und DMF die α-Aminosäurechlorid-Verbindungen cis-, trans-MCl2(NH2CHRCOCl)2 (2) erhalten, welche mit N-(Trimethylsilyl)-α-aminosäureestern die Dipeptid-Komplexe cis-, trans-MCl2(DipeptidOR)2 (R = H, Alkyl, SiMe2) (3) liefern. trans-Palladium-Komplexe vom Typ 3 und vom Typ cis-PdCl2(His-NHCHRCO2Et) (4) entstehen auch aus den entsprechenden α-Aminosäure-Komplexen und dem α-Aminosäureester mit einem wasserlöslichen Carbodiimid.

Notes: Bis(2,4,6-tri-tert-butylphenyl)ditellan (1) wird durch Oxidation von Lithium-(2,4,6-tri-tert-butylphenyl)tellurid in Form roter, stark lichtbrechender Kristalle erhalten. 1 kristallisiert monoklin in der Raumgruppe C2/c. Der Bindungsabstand d(Te-Te) beträgt 271.3 pm, der Bindungswinkel an den Te-Atomen 100.6° und der Torsionswinkel an der Te-Te-Bindung 92.1°. Durch die C2-Symmetrie besitzen die beiden ortho-ständigen tert-Butylgruppen der Substituenten unterschiedliche chemische Umgebung, die auch in Lösung bei tiefen Temperaturen erkennbar wird. Aus NMR-spektroskopischen Daten gelang erstmals die Bestimmung der Rotationsbarriere um eine Te-Te-Bindung; sie beträgt 40.9 kJ · mol-1. Dieser Wert ist um 20% kleiner als für das entsprechende Diselan.

Notes: On treatment with Ti(OiPr)4, 4-hydroperoxy-4-methyl-2,5-cyclohexadien-1-one (1) and 10β-hydroperoxy-1,4-estradiene-3,17-dione (3), readily available by photooxygenation of p-cresol and estrone, respectively, were converted to the corresponding epoxy quinols 5 and 6a, b. Also significant amounts of the respective quinols 2 and 4 were obtained, which could be transformed in high yields into 5 and 6a, b by Sharpless oxidation with tert-butyl hydroperoxide using Ti(OiPr)4 or VO(acac)2 as catalysts. Epoxidation of the quinol 4 with m-CPBA led preferentially to the lactone 7 by Bayer-Villiger rearrangement, showing the advantage of the present synthetic method.

Notes: 1,1-Dichlor-2,2,3,3-tetramethylcyclopropan (1a), 7,7-Dichlor- und 7,7-Dibromnorcaran (1b) reagieren mit Magnesiumanthracen·3THF (2) unter stufenweiser radikalischer Reduktion zu 9a, b bzw. 11a, b und 10, zu Carbenprodukten 6a, a′, b und 7a, b sowie zu Alkylierungsprodukten 4a, b und 5a, b. Die Verteilung der Reaktionsprodukte ist in starkem Maße vom Substrat und von den Reaktionsbedingungen abhängig: 1a wird beispielsweise in Toluol mit hoher Selektivität zu 9a reduziert, während in THF bei tiefer Temperatur 4a und 5a Überwiegen. Der für die Reaktion von 1a mit 2 vorgeschlagene Reaktionsablauf wird durch Deuterierungsversuche unterstützt. α,α-Dichlorcyclobutanone 12a-e lassen sich mit 2 in THF in mäßigen bis guten Ausbeuten zu α-Chlorcyclobutanonen 13a-e reduzieren, 12d liefert dabei in hoher Reinheit das endo-13d. Die Reduktion von 2-Halogenketonen 15a-f mit 2 in THF zu den Ketonen 16a-f ist nur in geringen bis mäßigen Ausbeuten möglich.

Notes: Die Iminoborane XB≡NtBu 1a-c (X = Me, Et, Bu) addieren in Gegenwart von tmeda Lithiummethanid LiMe im Verhältnis 2:1 unter Ausbildung der Cyclobuten-homologen Azaboraazoniaborata-Ringverbindungen 3a-c. In Lösungen von 3a-c fluktuiert die Li(tmeda)-Gruppe zwischen den Ring-N-Atomen. Die röntgenographische Bestimmung der Struktur von 3a ergibt eine an ein Ring-N-Atom fixierte Li(tmeda)-Gruppe und einen nicht planaren Vierring mit 4 ungleichen BN-Abständen zwischen 142.5 und 163.3 pm; die Beschreibung der Struktur wird durch die Bestimmung von Deformationselektronendichten ergänzt. Die stabileren Imonoborane 1d, e [X = tBu) N(tBu)-SiMe3], z. T. auch 1c, addieren die Lithiumalkanide LiR (R = Me, Bu, tBu) regio- und stereospezifisch zu den kristallinen Aminoboranen R-(X)-B=N(tBu) -Li(tmeda) mit einer elektrophil leicht austauschbaren Li(tmeda)-Gruppe. Die Verbindung tBu2B=N(tBu)-Li(tmeda) (2g) kristallisiert monoklin mit einem für eine relativ kurze BN-Doppelbindung typischen Abstand von 138.3 pm.

Notes: 2,4-Diaryl-4-(2,4-dinitroaryl)-5(4H)-oxazolones 2 were prepared by arylation of the corresponding 5(4H)-oxazolones 1 under phase-transfer conditions with the corresponding 1-halo-2,4-dinitrobenzenes. 2,4-Diaryl-4-(3,5-dinitro-2-pyridyl)-5(4H)-oxazolones 5 were obtained similarly from the corresponding 1 and 2-chloro-3,5-dinitropyridine. On reaction with methanol and p-toluenesulfonic acid, oxazolones 2 rearranged to the corresponding 1-hydroxy-1H-indazole derivatives 8. Under the same conditions oxazolones 5 afforded a mixture of the correspondingly substituted 1H-pyrazolo[4,3-b]pyridines 7 and substituted imidazo[1,5-a]pyridines 12. In all cases the solvolysis reaction, yielding substituted glycine esters 9 and 11, was competitive with the rearrangement. Reaction paths are discussed.

Notes: Bei der Umsetzung von 8-Methoxy-2,7-octadiensäure-ethylester (1) mit Quecksilber(II)-acetat in Gegenwart von Calciumoxid und Methanol und anschließender NaBH4-Reduktion wird regioselektiv in 90proz. Ausbeute ein Gemisch von cis- und trans-[2-(Dimethoxymethyl)cyclopentyl]essigsäure-ethylester (cis-2a und trans-2a) erhalten. Unter analogen Reaktionsbedingungen entsteht aus (1′S,3′S)-3-[3-(2-Methoxyethenyl)-1,2,2-trimethylcyclopentyl]propensäure-ethylester (3) regio- und stereoselektiv in 70 proz. Ausbeute nur (1′S,2′S,3′R,4′R)-[3-(Dimethoxymethyl)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]essigsäure-ethylester (4a). Damit ist sichergestellt, daß die radikalische Cyclisierung von optisch aktiven Derivaten von 1 unter den angegebenen Reaktionsbedingungen nicht nur regioselektiv, sondern auch mit hoher Stereoselektivität verläuft.

Notes: The kinetics of thermal decomposition of cuneane2) (1) in the gas phase have been investigated in the temperature range 180-220°C. The reaction is a clean first-order homogeneous process leading to the formation of two C8H8 isomers, viz., semibullvalene3) (2) and cyclooctatetraene (3). The rate constant varies with temperature according to the Arrhenius equation log(k/S-1) = (13.82 ± 0.09) - (37.7 ± 0.2 kcal mol-1)/RT In10. The Arrhenius parameters are consistent with a biradical mechanism leading to the formation of semibullvalene (2). The product proportions are pressure-dependent which strongly suggests that semibullvalene (2) is initially formed with high vibrational energy content (ca. 74 kcal mol-1) and can react further to give cyclooctatetraene (3).

Notes: Trapping Reactions for Unstable [1-Chloro-2,2,2-trifluoro-1-(trifluoromethyl)ethyl] Dialkyl PhosphitesThe reaction of ClP(OR)2 1a-d (R = Me, Et; R-R = CH2CH2, CMe2CMe2) with hexafluoroacetone yields the thermally unstable phosphites ClC(CF3)2OP(OR)2 4a-d besides other products. Trimethyl phosphite converts 4a-d into the phosphates (MeO)2P(O)OC(CF3)2P(OR)2 (R = Me, Et) 5a and b and the phosphonates (MeO)2P(O)C(CF3)2OP(OR)2 (R-R = CH2CH2, CMe2CMe2) 5c and d, Compounds formed in an Arbuzov reaction.

Notes: Beim Versuch, Dimethylphosphansulfid Me2P(S)H durch Umsetzung mit Me2N—SiMe3 in den Silylester der Dimethylthiophosphorigen Säure Me2P—S—SiMe3 zu überführen, wurde neben (Me3Si)2S ausschließlich das Diphosphanmonosulfid Me2P—P(S)Me2 (3b) erhalten. Die Übertragung dieses Reaktionsprinzips auf die disekundären Phosphansulfide MeH(S)P—[CH2]n—P(S)-MeH (n = 3,4; 6a, b) macht die Monosulfide der 1,2-Diphospholane bzw. 1,2-Diphosphinane 7a bzw. 7b zugänglich. Oxidative Addition von Tetrachlor-o-benzochinon an 7a bzw. 7b liefert Oxyphosphorane mit λ4P—λ5P-Strukturelementen.

Notes: Das durch zweifache Deprotonierung des Esters 5a erzeugte Enolat 7a wird an Aldehyde addiert. Dabei werden die Einflüsse von Enolat-Gegenion, Lösungsmittel und Reaktionstemperatur auf das Verhältnis der isomeren Produkte 9:10 untersucht. Die höchsten Diastereoselektivitäten lassen sich mit dem Magnesiumenolat 7a (M = MgX) erzielen. Alkalische Hydrolyse der Addukte 9/10 führt unter Rückgewinnung des chiralen Hilfsmittels Triphenylglycol (6a) zu β-Hydroxycarbonsäuren 11 mit entsprechender optischer Reinheit. Die Aldolreaktionen der zweifach deprotonierten Ester 5b-f liefern erste Hinweise auf die Strukturparameter, die für die hohe Diastereoselektivität des Acetats 5a ausschlaggebend sein könnten. Ungewöhnliche Umlagerungen treten in den Massenspektren des Diols 6a sowie der Ester 5a, 5b, 5d und 9a-c auf.

Notes: Green, crystalline Cp3U=CHPMe3 has been synthesized by the reaction of Cp3UCl with Li[CH2]2PMe2 or CH2=PMe3. Its crystal structure has been determined by single crystal X-ray diffraction. The short U=CH bond distance, 2.274(8) Å, and large U—C—P angle, 143.5(5)°, indicate uranium-carbon multiple bond character. The 1J(13C1H) coupling constants within the CH group between uranium and phosphorus in Cp3U=CHPPh2Me (95 Hz), Cp3U=CHPMe2Ph (100 Hz), and Cp3U=CHPPh2Me (113 Hz) are surprisingly small, but no agostic interaction UCHP can be derived from the structural data.

Notes: Umsetzung der N-Phthaloylthreonin- oder -allothreonin-methyl-ester 3 mit Trifluormethansulfonsäureanhydrid/Pyridin in Dichlormethan führt in quantitativer Ausbeute zu Threonin- bzw. Allothreonin-trifluormethansulfonaten 4, mit denen sich Aromaten in Gegenwart von Trifluormethansulfonsäure unter Erhaltung der Konfiguration an C-2 der Aminosäuren zu β-Methyl-N-phthaloylphenylalanin-methylestern 6 alkylieren lassen. Bezüglich der Konfiguration an C-3 der Aminosäuren reagieren die Threonin-Derivate 4b (2R,3S) und 4c (2S,3R) unter fast vollständiger Retention zu 6e (2R,3R) und 6f (2S,3S), während mit den Allothreonin-Derivaten 4e (2R,3R) und 4f (2S,3S) weitgehend Racemisierung erfolgt. Die überraschende stereoselektive Aromatenalkylierung mit den Verbindungen 4b, c wird durch Rotationshinderung bei gleichzeitiger Rückseitenabschirmung des intermediären Carbokations durch die N-Phthaloylgruppe gedeutet.

Notes: Die Allencarbonsäure-arylester 4a-o und die Allencarboxanilide 9a,b,e,h und 1, die sich jeweils lediglich durch die Anzahl oder die Größe der am Aromaten befestigten Alkylgruppen unterscheiden, werden auf dem Ylidweg über entsprechend substituierte 2-Halogen-, 2-Phosphonio- und 2-Phosphoranylidenessigsäure-Derivate (1→2→3→4 bzw. 6→7→8→9) hergestellt und in siedendem Xylol in die tricyclischen Verbindungen 5 bzw. 10 übergeführt. Die Geschwindigkeitsunterschiede bei dieser Intramolekularen Diels-Alder-Reaktion werden diskutiert.

Notes: Die Cothermolyse von weißem Phosphor (P4) und [(η5-C5Me5)2-(CO)nW2] (1; n = 4, 6) sowie [(η5-C5Me4R)V(CO)4] (3) ergibt die Tripeldecker-Sandwichkomplexe [{η5-C5Me5)W}2(μ,η6-P6)] (2) und [{η5-C5Me4R)V}2(μ,η6-P6)] (4a, R = CH3; 4b, R = C2H5). 2 und 4b wurden kristallstrukturanalytisch, 2 und 4a sowie A und B elektrochemisch, ESR- und elektronenspektroskopisch charakterisiert. Es wird eine empirische Valenzelektronenregel für Tripeldecker-Komplexe abgeleitet.

Notes: Wir beschreiben eine neue, ergiebige Synthese von Hexachlortropon (6) und einige Kondensationsreaktionen von 6 zu neuen polychlorierten, gekreuzt konjugierten Cycloheptatrienderivaten. Umsetzungen von Octachlorcycloheptatrien (5) mit Benzol/CF3SO3Ag bzw. mit Phenylmalononitril (28) führen zu ersten stabilen [1.6.7]Chinarenen 19 und 29. Die Struktur von 19 wird mit Hilfe einer Röntgenstrukturanalyse bewiesen und ein Bildungsweg vorgeschlagen. Der Einfluß der Polychlorierung auf Stabilität und Elektronenspektren wird diskutiert.

Notes: 2-Nitrophenylsulfenimines 2 of large structural variety are easily available from 2-nitrophenylsulfenamides 1, by direct and indirect electrochemical oxidation or by using stoichiometric amounts of a triarylamine radical cation salt. In most cases the direct electrochemical method is to be preferred, because of the convenient reaction procedure and the simple workup of the products. Inter- and intramolecular addition of nucleophiles to the C — N double bond is possible as shown by two examples.

Notes: Diels-Alder-Reaktion von 3,4-Hexamethylenfuran mit Acrylsäure führt mit hoher endo-Selektivität zur Carbonsäure 1a, die über ihre α-Phenylethylammonium-Salze in die Enantiomere getrennt wurde. Sowohl der Vergleich der CD-Spektren von (-)-1a und (-)-3 als auch die Röntgenstrukturanalyse des Camphansäureesters 4b legen die 1R,2S,4S-Konfiguration von (-)-1a fest. Ozonolyse des Esters (-)-1b liefert das 2,5-überbrückte, all-cis- und RSS-Konfigurierte Tetrahydrofuran (-)-5, das sich in 22proz. Ausb. mit Natriummetaperiodat/Kaliumpermanganat zum γ-Lacton (2R,3S)-(-)-6 oxidieren läßt. Die Hydridreduktion von (-)-6 unter verschiedenen Bedingungen ergibt die optisch aktiven γ-Bislactone (-)-8 und (-)-9 bzw. das Bislactol 10. (-)-8 besitzt die gleiche absolute Konfiguration an allen Chiralitätszentren wie das natürlich vorkommende Bislacton (-)-Canadensolid.

Notes: Preparation and Characterisation of Hexakis(trifluoromethyl)digermachalcogenanesReactions of (CF3)3GeI (2a) with HgS or Ag2Se and of (CF3)3GeCl (2b) with (t-BuMe2Si)2Te (3) lead to new compounds of the type [(CF3)3Ge]2E (E = S, Se, Te) (1b-d). 19F-, 13C-, and 77Se-NMR as well as IR- and MS data of the compounds are presented and discussed.

Notes: Synthesis and Structure of Manganese(II) L-Aspartate Trihydrate, Mn(L-Asp)· 3H2OManganese L-aspartate chloride, Mn(L-AspH)Cl, has been prepared from equimolar quantities of MnCl2 and Mn(L-AspH)2 in water. This material can be converted into the title compound by treatment with aqueous KOH, and crystallized as a trihydrate from solutions kept at pH = 7.85. The compound has been characterized by elemental analysis and by single crystal X-ray structure determination. In the crystal, the aspartate dianion functions as a facially tridentate ligand to the Mn(II) center whose octahedral coordination sphere is completed by two water molecules and a carboxylate oxygen atom from a neighboring complex in trans position to the amino group. The stereochemistry of this coordination mode is different from that in the analogous magnesium compound, but similar to that in the cobalt(II) and zinc(II) analogues. The third water molecule is a hydrogen-bonded crystal water.

Notes: Arene(Phosphane)metal complexes, XIV.  -  Synthesis of η5-Cyclohexadienyl- and η4-Cyclohexa-1,3-diene Osmium Complexes from [C6H6Osl(PR3)2]PF6The reaction of [C6H6OsI(PR3)2]PF6 (1,4) with NaBH4 in ethanol leads almost quantitatively to the formation of the η5-cyclohexadienyl complexes (η5-C6H7OsI(PR3)2 (5: R = Me; 6: R = Ph). Reduction of 5 with Na in THF gives the highly reactive [(η5-C6H7)Os(PMe3)2]- anion which reacts with NH4PF6 in the presence of iodide to produce the compounds (η5-C6H7OsH(PMe3)2 (8) and (η4-C6H8)OsHI(PMe3)2 (9).

Notes: Deprotonation of 9,10-dihydroanthracene (2) affords the monoanion 6 which is subjected to alkylation reactions with mono and bifunctional electrophiles. Crucial intermediates in syntheses using 6 are 9-(3-bromopropyl)-9,10-dihydroanthracene (7) and 1,3-bis(9,10-dihydro-9-anthryl)propane (9) since they provide access to linear oligomers in which 9,10-dihydroanthracene units are linked by trimethylene groups. The alkylation processes of these species can be extended to the structurally related polymer 4. The regio- and stereoselectivity of the alkylation reactions are investigated by 1H- and 13C-NMR spectroscopy.

Notes: In dieser Arbeit berichten wir über die Synthese neuer photochromer 1,8a-Dihydroindolizine (DHI) bzw. 1,8a-Dihydro-5-azaindolizine 19 und Betaine 18 sowie über die Darstellung der als Vorstufen benötigten 3,3-Diaryl-3H-pyrazole 13 bzw. der Cyclopropene 15. Die Struktur der Betaine 18 wird durch die Kristallstrukturanalyse von 181 erstmals eindeutig gesichert. Im letzten Teil wird eine Struktur-Reaktivitäts-Beziehung der UV-spektroskopisch bestimmten Cyclisierungsgeschwindigkeiten mit Hammett-Parametern vorgenommen und Studien zum Mechanismus des thermischen Ringschlusses 18→19 durch MINDO/3-Rechnungen an einem Modellsystem beschrieben.

Notes: (η5-C5Me5)(CO)(NO)ReBr (3), hergestellt aus [η5-C5Me5)(CO)2-(NO)Re]BF4 und (Bu4N)Br, reagiert mit LiP(SiMe3)2 zum Disilylphosphidorheniumkomplex (η5-C5Me5)(CO)(NO)ReP(SiMe3)2 (4). Komplex 4 wird von 2,4,6-(tBu)3C6H2PCl2 in den nur in Lösung stabilen Diphosphenylkomplex (η5-C5Me5)(CO)(NO)Re—P=P—C6H2(tBu)3-(2,4,6) (5) übergeführt. Behandlung von 5 mit [(Z)-Cycloocten]Cr(CO)5 liefert das stabile Pentacarbonylchromderivat (η5-C5Me5)(CO)(NO)Re[Cr(CO)5]P=P—C6H2(tBu)3-(2,4,6) (7). Zu Vergleichszwecken wurden die Komplexe (η5-C5Me5)(CO)(NO)Mn[Cr(CO)5]P=P—C6H2(tBu)3-(2,4,6) (9) und (η5-C5Me5)(CO)2Fe[Cr(CO)5]P=P—C6H2(tBu)3-(2,4,6) (10) synthetisiert. Von 10 wurde eine Röntgenstrukturanalyse durchgeführt.

Notes: Die Reduktion von RuCl2(pp3) [pp3 = P(CH2CH2CH2PMe2)3] mit Natriumamalgam in Benzol und Toluol sowie in o-bzw. m-Xylol ergab die Arylruthenium-Derivate RuH(C6H5)(pp3) (1), RuH(C6H4Me-3)(pp3) (2), RuH(C6H3Me2-3,4)(pp3) (3) und RuH(C6H3Me2-3,5)(pp3) (4). Komplex 2 wurde als Gemisch zweier Isomere erhalten, in denen der meta-Methylsubstituent Positionen besetzt, die von der Ru—H-Einheit abgewandt (2a) oder ihr zugewandt (2b) sind. Die Molekülstrukturen von 2a, 2b, 3 und 4 wurden röntgenographisch ermittelt.

Notes: Die Komplexe C5H5Rh(=C=CHR)P(iPr)3 (1,3,5) reagieren mit Benzoylazid nahezu quantitativ zu den Metalla-Heterocyclen (2, 4, 6). Für 6 (R = Me), nicht jedoch für 4 (R = Ph), ist die Bildung von E/Z-Isomeren nachweisbar; ihr Verhältnis ist solvensabhängig. Die Protonierung von 4 und 6-E/6-Z mit CF3CO2H in Gegenwart von NH4PF6 führt unter Angriff des Protons am Ring-Stickstoffatom zu den PF6-Salzen der Komplexkationen 7 und 8, die ebenfalls E/Z-Isomere bilden. Bei der Reaktion von 3 mit Phenylazid entsteht zunächst die Z-Form der Ketenimin-Verbindung C5H5Rh(C,N-η2-PhN=C=CHPh)P(iPr)3 (9), die in Lösung relativ rasch eine Umlagerung zu dem E-Isomeren (bis zu einem Verhältnis 9-Z:9-E = 1:1) eingeht.

Notes: Syntheses of Pyrazolo-1,2,4-triazine Derivatives of 1,6-Methano [10] annuleneCoupling reactions of the diazonium betains 3, 4, 5 with 3-tert-butoxy-1,6-methano[10]annulene (2) under mild reaction conditions lead to elimination of tert-butyl alcohol with formation of the methano-bridged triazine dye stuffs 6a-c. For comparison by coupling reactions of 3-5 with β-naphthol followed by cyclisation reactions the triazine dye stuffs 8a-c are obtained. Their spectroscopic properties were compared with 6a-c.