Reactions of acetylenes with noble-metal carbonyl halides.10. Synthesis and X-Ray structural Characterization of a new substituted diplatina-dioxapentalene complex [CL(CO)PT(CME=C(COOME)C(=O))PTCL(PPH3)]

The complex cis-[Pt(CO)2CI2], in chloroform solution at room temperature, reacts with methyl 2-butynoate in the presence of water and carbon monoxide to give [Cl(CO)Pt{CMe=C(COOMe)C(=O)}Pt(CO)CI] (1). Complex (1) is easily transformed into the related triphenylphosphine derivative [Cl(CO)Pt{CMe=C(COOMe) C(=O)}PtCl(PPh3)] (2). A multinuclear (1H, 195Pt and 31P n.m.r. study of complex (2) is reported. The analysis of the spectrum gave unambiguously the value 3J(Pt-Pt) = 818 Hz. The crystal contains discrete molecules of (2) with square-planar arrangements around the Pt atoms showing large angular distortions due to the two five-membered rings. The two fused metallacycles and the two co-ordination planes are essentially coplanar, giving a flat molecule.