Novel sandwich cations of platinum with tetramethyl-cyclobutadiene and cyclopentdienyl or hexamethylbenzene ligands

Abstract

Highly reactive cations [Pt(η⁴-C₄Me₄)(solv)_x]²⁺(solv = acetone or nitromethane) can be obtained from [{Pt(η⁴-C₄Me₄)Cl₂}] by chloride abstraction with AgCF₃SO₃. The solvento complex [Pt(η⁴-C₄Me₄)-(Me₂CO)_x][CF₃SO₃]₂ reacts with cyclopentadines and with hexamethylbenzene to form the sandwich compounds [Pt(η⁴-C₄Me₄)(dienyl)]CF₃SO₃(dienyl =η⁵C₅Me₅, η⁵-C₅H₄Me or η⁵-C₅H₅) and [Pt(η⁴-C₄Me₄)(η⁶-C₆Me₆)][CF₃SO₃]₂·Me₂CO. The new compounds are characterised by ¹H, ¹³C and ¹⁹⁵Pt NMR spectroscopy and cyclic voltammetry. The structure of the hexamathylbenzene complex, determined by X-ray crystallography, reveals an average Pt–C distance of 2.138 Å for the C₄Me₄ ligand and 2.351 Å for the C₆Me₆ ligand indicating a pronounced structural trans effect.