DISTORTION OF CYCLOPENTADIENYL RINGS IN ETA(5)-CYCLOPENTADIENYL PALLADIUM COMPLEXES - CRYSTAL-STRUCTURES OF [PD(C5H5)CL(PME2PH)] AND [PD(C5H5)(PH2PCH2CH2PPH2)][PF6]

The structures of [Pd(C5H5)Cl(PMe2Ph)] and [Pd(C5H5)(dppe)]PF6 (dppe = Ph2PCH2CH2PPh2) have been determined by X-ray analysis. Both are eta5 -cyclopentadienyl compounds, with the Cp ring nearly perpendicular to the PdPCl or PdP2 plane. Comparison of their molecular geometries with those of other cyclopentadienyl-palladium complexes of the types PdCp LL' and PdCpL2 reveals the existence of a complete range of ring-PdLL' or ring-PdL2 orientations and suggests that the usual assignment of s tructures of these types as either staggered or eclipsed is not realis tic. Likewise, the patterns of long and short C-C bonds of the Cp ring s do not in general follow the sequences expected for the idealized ge ometries, although large librational distortions of the C5H5 rings in most of the compounds limit the accuracy of these determinations. The lengths of the Pd-C(Cp) bonds appear to be much more dependent on the relative trans influences of L and L' than on the ring orientations.