ISSN:
1432-2234
Keywords:
Diphosphene
;
Diphosphenyl radical (HP2)
;
Geometric isomerization
;
Isosceles triangle
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Summary The geometric isomerization and the dehydrogenation of HP=PH in the ground and some low-lying excited states are investigated by theoretical calculations. The reaction paths are traced by either the CASSCF or UHF-SCF calculations using the 6-31G(d,p) basis functions, and the accompanying energy changes are calculated by the MRD-CI method employing the [5s3p1d]/[2s1p] basis functions. The barrier heights for the trans-to-cis isomerization, by the planar inversion and the nonplanar twisting, in the ground state are calculated to be 265 and 144 kJ/mol (with the vibrational zero-point energy corrections), respectively. The latter barrier is noticeably lower than the H-P and the P-P bond dissociation energies oftrans-HP=PH (1Ag), which are 304 and 271 kJ/mol, respectively. The ground-state HP2 radical (2A'), which is to be formed by the dehydrogenation of HP=PH, should suffer further decomposition into P2 (1Σ g + ) and H with an activation energy of 139 kJ/mol. The lowest excited state of HP2 is found to be a hydrogen-bridged 3π-electron system (2A2) having an isosceles triangle structure. It has proved to be formed by the dehydrogenation of the lowest excited singlet state (1B) of HP=PH via a transition state which lies 194 kJ/mol above the1B state. The excited HP2 (2A2) is state-correlated with P2 (3Δu)+H.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01134201
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