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

Abstract

η 1-Alkynylplatinum(II) complexes of the type (cod)Pt(CCR) 2 ( 1, cod=η 4-cycloocta-1,5-diene; R=Me ( a), t Bu ( b), Ph ( c), Fc ( d), SiMe 3 ( e)) were prepared in good yields from the reaction of (cod)PtCl 2 with either HCCR and NaOEt (R= t Bu, Ph, Fc) or di(1-alkynyl)dimethyltin, Me 2Sn(CCR) 2 (R=Me, SiMe 3). The analogous reaction of [P]PtCl 2 ([P]=tri(1-cyclohepta-2,4,6-trienyl)phosphane, {P(C 7H 7) 2(η 2-C 7H 7)}) with Me 2Sn(CCR) 2 (R=Me, t Bu, Ph, Fc, SiMe 3), 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 C 7H 7 rings is η 2-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(C 7H 7) 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 C 7H 7 rings to platinum.