Acetylenes and noble-metal compounds. Part 15. Reactions of dialkylacetylenes with bis(acetonitrile)dichloroplatinum(II) and tin(II) chloride to give ionic cyclobutadieneplatinum–tin complexes

Abstract

Acetylenes (C₂R₂, R = Me or Et) react with [Pt(NCMe)₂Cl₂] and SnCl₂ to give the ionic tetra-alkylcyclobutadiene complexes [Pt₂(C₄R₄)₂Cl₃][Pt(C₄R₄)(SnCl₃)₃](2) which can be converted into the tin-feer complexes [Pt₂-(C₄R₄)₂Cl₄](3) by reaction with HCl and acetone, or into the salts [N(PPh₃)₂][Pt(C₄R₄)(SnCl₃)₃](4) plus (3) by reaction with [N(PPh₃)₂]Cl. Structures are assigned on the basis of spectroscopic data, in particular the intensities of the ¹⁹⁵Pt, ¹¹⁷Sn, and ¹¹⁹Sn satellites of the methyl resonances in the ¹H n.m.r. spectra of (2 and 4; R = Me). Two new complexes of di-t-butylacetylene (2,2,4,4-tetramethylhex-3-yne), [Pt(C₂Bu^t₂)(NCMe)(SnCl₃)-Cl] and [Pt₂(C₂Bu^t₂)₂(SnCl₃)₂Cl₂], are also described. The mechanism of the acetylene dimerisation reaction leading to (2) is discussed by comparison with the acetylene oligomerisation reactions induced by Pd^II.