THE STRUCTURE OF GOLD(I) CYCLOPENTADIENE COMPLEXES - X-RAY-DIFFRACTION STUDIES OF (PH2C5H3)AUPPH3 PENTANE SOLVATE

The crystal and molecular structures of (Ph2C5H3)AuPPh3 pentane solvat e were determined by X-ray diffraction (MoKalpha radiation, graphite m onochromator, omega scan mode, R = 0.0256 for 2323 reflections). Cryst als are orthorhombic, a = 12.550(5), b = 22.161(6), c = 22.362(8) Angs trom, V = 6219(4) Angstrom(3), Z = 8, space group Pbca. The gold atom forms two almost collinear bonds with the P atom of triphenylphosphine ligand and C(1) atom of 2,5-diphenylpentadiene ligand. The Au-C and A u-P bond lengths are 2.115(9) and 2.275(2) Angstrom, respectively. The ratio of C-C bond lengths in the cyclopentadiene ring corresponds to a diene structure: the C(2)-C(3) and C(4)-C(5) bonds [1.38(2) and 1.38 (2) Angstrom] are shorter than C(1)-C(2) [1.47(1) Angstrom], C(1)-C(5) [1.46(2) A], and C(3)-C(4) [1.42(2) Angstrom]. The phenyl substituent s are turned against the plane of the five-membered ring by 11.3 degre es and 15.2 degrees. The cyclopentadiene ring is slightly folded (4.6 degrees) along the C(2)... C(5) Line. The gold atom is situated unsymm etrically relative to the cyclopentadiene ligand. The exocyclic bond a ngles AuCC (109.7 degrees and 101.9 degrees) are different; the latter is smaller than the ideal tetrahedral angle. The mode of Cp coordinat ion to Au is regarded as being intermediate between eta(1) and eta(2). The distinctions in the geometries of a series of Au(I) complexes wit h substituted cyclopentadiene ligands are discussed in the context of structural modeling of migration processes.