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-(PhC[triple bond, length half m-dash]C)2Ti(η-C5H5)2}(PR3)] in which the PhC[triple bond, length half m-dash]C–Ti–C[triple bond, length half m-dash]CPh group acts as a bidentate ligand to platinum. In contrast, dimethylbis(phenylethynyl)silane reacts with [Pt(C2H4)2(PR3)][PR3= P(C6H11)3, PMeBut2, or PPri2Ph] to give diplatinum complexes [Pt2(σ-C[triple bond, length half m-dash]CPh){µ-(1-σ:1–2-η-C[triple bond, length half m-dash]CPh)}(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(C[triple bond, length half m-dash]CPh)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-Kα 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 C[triple bond, length half m-dash]CPh groups are σ-bonded to one metal atom (formally PtIV) but one is also η2-co-ordinated to the other platinum (formally PtII). 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-PhC[triple bond, length half m-dash]CSi(C2Ph)Me2}(PPh3)2] and [Pt2{η-(PhC[triple bond, length half m-dash]C)2SiMe2}(PPh3)4].