η1-Alkynylplatinum(II) complexes with cycloocta-1,5-diene and tri(1-cyclohepta-2,4,6-trienyl)phosphane ligands

η1-Alkynylplatinum(II) complexes of the type (cod)Pt(CCR)2 (1, cod=η4-cycloocta-1,5-diene; R=Me (a), tBu (b), Ph (c), Fc (d), SiMe3 (e)) were prepared in good yields from the reaction of (cod)PtCl2 with either HCCR and NaOEt (R=tBu, Ph, Fc) or di(1-alkynyl)dimethyltin, Me2Sn(CCR)2 (R=Me, SiMe3). The analogous reaction of [P]PtCl2 ([P]=tri(1-cyclohepta-2,4,6-trienyl)phosphane, {P(C7H7)2(η2-C7H7)}) with Me2Sn(CCR)2 (R=Me, tBu, Ph, Fc, SiMe3), afforded selectively the complexes [P]PtCl(CCR) 2a–e in high yield, in which the 1-alkynyl group is in cis position with respect to the phosphorus atom, and one of the C7H7 rings is η2-coordinated to platinum through the central CC bond. Complexes 3a–e of the type [P]Pt(CCR)2 could not be prepared by the reaction of 2 with an excess of the 1-alkynyltin reagents. However, the reaction of 1 with the phosphane P(C7H7)3 gave compounds 3a–e in quantitative yield by substitution of the cod ligand. The molecular structures of 2b and 3d were determined by X-ray structure analysis, and complexes 1–3 were characterised in solution by multinuclear magnetic resonance spectroscopy (1H-, 13C-, 29Si-, 31P-, 195Pt-NMR). The structures of 2 and 3 in solution were found to be fluxional with respect to coordination of the C7H7 rings to platinum.