Reactions of platinum(II) acetylides with organolithium compounds: formation of lithium-bridged dinuclear platinum(II) complexes and of triorganoplatinate(II) complexes: Crystal structure of the complex [Pt2(C≡CPh)4(PEt3)2(Bu n)2(μ-Li)2]

Abstract

Platinum(II) acetylides of the type trans-[Pt(C≡CR1)2(PEt3)2] (1) (R1 = Me, Bun, or Ph) lose one equivalent of PEt3 on treatment with organolithium reagents LiR2 (2) (R2 = Bun, But, or Ph) in hydrocarbon solvents to give the dinuclear complexes [Pt2(C≡CR1)4(PEt3) 2(R2)2(μ-Li)2] (3), containing a PtLi2Pt unit. In the presence of better donors (e.g. Et2O, tetrahydrofuran, or NNN′N′-tetramethylethylenediamine) solvation of lithium breaks this dimeric structure leading to the anions (4) of the type trans-[Pt(C≡CR1)2(PEt3)R 2]-. Reaction of the anion (4d) (R1 = Ph, R2 = Bun) with a further equivalent of LiR2 (R2 = Bun) gave Li(C≡CPh) and another anion, cis-[Pt(C≡CPh)(PEt3)(Bun)2]-. Multinuclear n.m.r. (1H, 7Li, 13C, 31P, and 195Pt) has been used to characterize the highly reactive compounds in solution. The crystal structure of complex (3d) (R1 = Ph, R2 = Bun) has been determined, which crystallises in space group P21/n, with a = 14.061(4), b = 18.408(4), c = 19.737(7) Å, and Z = 4.