Synthesis of heterobimetallic complexes containing cobalt–platinum or rhodium–platinum dative bonds. Molecular structure of [(η5-C5H5)(CO)2Rh→Pt(C6F5)2(CO)]

Abstract

The complexes [(η⁵-C₅R₅)(CO)LM→Pt(C₆F₅)₂(CO)](R = H or Me; M = Co or Rh; L = CO or PPh₃) have been obtained by reacting the bases [M(η⁵-C₅R₅)(CO)L] with cis-[Pt(C₆F₅)₂(CO)(thf)](thf = tetrahydrofuran). Their structures are discussed on the basis of ¹H, ¹⁹F, and ³¹P n.m.r. and i.r. data. The molecular structure of the complex [(η⁵-C₅H₅)(CO)₂Rh→Pt(C₆F₅)₂(CO)] has been determined by an X-ray diffraction study: orthorhombic, space group P2₁2₁2₁ with a= 7.632 1(10), b= 16.415 1(17), c= 16.520 0(43)Å, Z= 4; R= 0.027, R′= 0.028 for 3 676 reflections with I 3σ(I) having 2 < 2θ < 60°. The structure shows that the basic (η⁵-C₅H₅)(CO)₂Rh group is co-ordinated to the Pt(C₆F₅)₂(CO) moiety forming a binuclear complex with an unbridged Rh–Pt bond of length 2.750(1)Å. Platinum is in an almost square-planar environment with the C₆F₅ groups mutually cis. The ¹⁹F n.m.r. spectra of the complexes reveal fluxional behaviour leading to equivalence of the two C₆F₅ groups. The reaction of [(η⁵-C₅R₅)(CO)₂Rh→Pt(C₆F₅)₂(CO)](R = H or Me) with PPh₃ yields [Rh(η⁵-C₅R₅)(CO)₂] and cis-[Pt(C₆F₅)₂(CO)(PPh₃)]; reacting [(η⁵-C₅H₅)(CO)₂Rh→Pt(C₆F₅)₂(CO)] with bis(diphenylphosphino)methane (dppm) gives [Rh(η⁵-C₅H₅)(CO)₂] and [Pt(C₆F₅)₂(dppm)].