摘要：

Reactions of [PtClR(cod)] with TlC5H4PPh2 yield dimeric complexes of the type [Pt2R2(mu-C5H4PPh2)2] (1a, R = Me; 1b, R = Et, 1c, R = Np; 1d, R = Ph). The crystal structure of 1a has been determined. The compound crystallizes in the monoclinic space group P2(1)/n with a = 10.155 (2) angstrom, b = 14.696 (3) angstrom, c = 21.080 (5) angstrom, beta = 90.02 (2)-degrees, V = 3146.0 (11) angstrom3, and Z = 4. Least-squares refinement converged at R = 0.0490 and R(W) = 0.0550 based on 6340 reflections with F > 4.0-sigma(F). The molecular structure reveals a structure of the type [Pt2Me2(mu-eta-5-C5H4PPh2)(mu-eta-1-1,1-C5H4PPh2)], in which the cyclopentadienyl group of one dppc ligand coordinates in the usual eta-5 mode, whereas the other is bound in eta-1 fashion, with both platinum and phosphorus attached to the same carbon atom giving a spirocyclic structure and a four-membered Pt2PC ring containing a Pt-Pt dative bond. The dimers are fluxional in solution at ambient temperature, but the solid-state structure of 1a is consistent with the NMR parameters obtained in solution at low temperature for all the complexes. A minor species is detected in solution for 1c and 1d, which is consistent with a symmetrical dimer of the type [Pt2R2(mu-eta-5-C5H4PPh2)2]. Crystals of 1d were obtained by slow evaporation of an ether solution and the crystal structure was determined. This compound crystallizes in the triclinic space group P1BAR with a = 10.256 (4) angstrom, b = 13.693 (5) angstrom, c = 14.687 (7) angstrom, alpha = 95.52 (3)-degrees, beta = 109.68 (3)-degrees, gamma = 101.87 (3)-degrees, V = 1869.7 (13) angstrom3, and Z = 2. Least-squares refinement converged at R = 0.0221 and R(W) = 0.0266 based on 6759 reflections with F > 6.0-sigma(F). The molecular structure reveals that both cyclopentadienyl groups are indeed bonded in eta-5 fashion, but the molecule is distorted and does not possess a center of symmetry. An equilibrium between the two forms in solution is proposed, and the symmetrical dimer, or a closely related analogue, is suggested to be an intermediate in the fluxional process observed for the unsymmetrical dimer at ambient temperature.

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