Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 12. Reaction of the complexes [PtW(µ-CC6H4Me-4)(CO)2(PR3)2(η-C5H5)] with carbon monoxide. Crystal structure of [Pt2W(µ3-CC6H4Me-4)(CO)4(PMePh2)2(η-C5H5)]

Abstract

Di- and tri-metal complexes [PtW(µ-CR)(CO)₃(PR′₃)(η-C₅H₅)](R = C₆H₄Me-4; PR′₃= PMe₃, PMe₂Ph, or PPh₃) and [Pt₂W(µ₃-CR)(CO)₄(PR′₃)₂(η-C₅H₅)](PR′₃= PMe₃, PMe₂Ph, PMePh₂, PPh₃, or PEt₃) have been isolated by treating toluene solutions of the compounds [PtW(µ-CR)(CO)₂(PR′₃)₂(η-C₅H₅)] with CO gas at 1 bar and room temperature. N.m.r. data (¹H, ¹³C-{¹H},³¹P-{¹H}, and ^l95Pt-{¹H}) for the new compounds are reported and a single-crystal X-ray diffraction study has been carried out on the complex [Pt₂W(µ₃-CR)(CO)₄(PMePh₂)₂(η-C₅H₅)]. The crystals are monoclinic, space group P2₁/c(no. 14), Z= 4, in a unit cell with a= 14.932 (13), b= 11.438(11), c= 26.394(24)Å, β= 97.42(7)°. Poor crystal quality resulted in refinement to R 0.075 (R′ O.080) for 2 488 reflections to 2θ⩽ 40° collected at ambient temperature. The study established that the molecular structure is based on a Pt₂W metal triangle, having a long Pt ⋯ Pt distance [2.989(3)Å], and capped by a CC₆H₄Me-4 group with the ligated carbon atom equidistant from all three metals. The terminal phosphine and carbonyl ligands on each Pt atom are unsymmetrically transoid with respect to the Pt ⋯ Pt vector, and the two carbonyl ligands on the W atom are semi-bridging to the Pt atoms, again unsymmetrically. The molecule possesses no symmetry. The nature of the Pt ⋯ Pt interaction, and the relationship between the complexes [Pt₂W(µ₃-CR)(CO)₄(PR′₃)₂(η-C₅H₅)] and previously reported di- and tri-platinum complexes with bridging alkyne ligands, are discussed.