Reactions of bis(ethylene)(tertiary phosphine)platinum complexes with phenylethynyl derivatives of titanium and silicon; crystal structure of (µ-dimethylsilanediyl)(σ-phenylethynyl)[µ-(1-σ:1–2-η-phenylethynyl)]-bis(tricyclohexylphosphine)diplatinum (Pt–Pt)

Abstract

Bis(ethylene)(tertiary phosphine)platinum complexes [Pt(C₂H₄)₂(PR₃)][PR₃= P(cyclo-C₆H₁₁)₃, PMe₂Ph, PMePh₂, PPh₃, or PPrⁱ₂Ph] react with bis(cyclopentadienyl)bis(phenylethynyl)titanium to give compounds [Pt{η-(PhCC)₂Ti(η-C₅H₅)₂}(PR₃)] in which the PhCC–Ti–CCPh group acts as a bidentate ligand to platinum. In contrast, dimethylbis(phenylethynyl)silane reacts with [Pt(C₂H₄)₂(PR₃)][PR₃= P(C₆H₁₁)₃, PMeBu^t₂, or PPrⁱ₂Ph] to give diplatinum complexes [Pt₂(σ-CCPh){µ-(1-σ:1–2-η-CCPh)}(µ-SiMe₂)(PR₃)₂]. A single-crystal X-ray diffraction study has established the structure of the product from [Pt(C₂,H₄)₂{P(C₆H₁₁)₃}] and [Si(CCPh)₂Me₂]. Crystals are monoclinic, space group P2₁/c(no. 14), with a= 12.44(1), b= 26.12(4), c= 15.832(8)Å, β= 97.99(6)°, and Z= 4. The structure has been determined by analysis of 5 131 unique data with F > 4σ(F) collected to 2θ⩽ 50°(Mo-K_α radiation) at 200 K on a four-circle diffractometer, and refined to R 0.053 (R′0.041). The results establish a molecular structure with an SiMe₂ group asymmetrically bridging a Pt–Pt separation of 2.703(1)Å. Two CCPh groups are σ-bonded to one metal atom (formally Pt^IV) but one is also η²-co-ordinated to the other platinum (formally Pt^II). The P–Pt–Pt–P skeleton is non-linear with PPtPt angles of 165.2(1) and 148.0(1)°. Dimethylbis(phenylethynyl)silane reacts with [Pt(C₂H₄)(PPh₃)₂], without carbon–silicon bond cleavage, to give mono- and di-platinum η² complexes [Pt{η-PhCCSi(C₂Ph)Me₂}(PPh₃)₂] and [Pt₂{η-(PhCC)₂SiMe₂}(PPh₃)₄].