ISSN:
1572-901X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Summary The trinuclear complexes {CpCo[P(O)(OMe)2]3}2Co and {CpCo[P(O)(OEt)2]3}2M, where M=Mg, Ca, Sr, Ba, Pb, Mn, Co, Ni, Cu, Zn, Cd or Hg, have been studied by x-ray diffraction methods and the crystal structures of {CpCo[P(O)(OR)2]3}2M [R=Me with M=Co (1) and R = Et with M = Cu (2)] have been solved by the heavy atom technique. Complex (2) crystallizes in the triclinic space group P 1 with two crystallographically independent molecules per unit cell. The cell dimensions area = 12.195(3) Å,b = 20.429(6) Å, c = 12.518(3) Å,α = 102.39(2)°, β=120.15(2)°, γ=92.28(2)°. The molecule contains two cobalt atoms and one copper atom in a linear arrangement with copper situated on a center of symmetry. Each of the cobalt atoms is bonded to a cyclopentadienyl ring and is connected to the central copper atom by three phosphonate groups acting as bridging ligands. Disorder phenomena within these phosphonate groups are best described as an enhanced thermal motion corresponding mainly to a rotation around the Co-Cu-Co axis. The CuO6 coordination octahedra exhibit a small (4+2) distortion. The electronic spectrum of this copper complex has been measured in solution and in the solid state and is in accord with the Jahn-Teller distorted octahedral coordination of the copper ion found in the x-ray structure. Complex (1) is monoclinic, space group P21/c with two formula units per cell. Its molecular structure shows the same general features as the copper complex. The coordination of the central cobalt atom is regularly octahedral within the limits of error. Parts of the phosphonate P(O)(OMe)2 groups are disordered over two distinct sites in the crystal with occupancy factors ofca. 0.75 and 0.25. D.s.c. measurements of the trinuclear compounds containing disordered P(O)(OEt)2 groups show phase transitions occurring in the 160–230 K temperature range that are best discussed in terms of order-disorder transitions. From d.s.c. measurements of the corresponding complexes with P(O)(OMe)2 ligands, there are no phase transitions visible in the 100–300 K range.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00619066
