Some platinum(II) complexes containing bis(diphenylphosphino)acetylene PPh2CCPPh2: synthesis, characterisation and crystal structures

Abstract

The reactivity of cis-[Pt(CCR)₂(COD)] (R = Bu^t, Ph) and cis/trans-[Pt(C₆F₅)₂(tht)₂] towards PPh₂CCPPh₂ (dppa) in several molar ratios has been explored. Treatment of cis-[Pt(CCR)₂(COD)] with 1 equiv. of dppa leads to novel alkynyl Pt(II) dimers [Pt₂(CCR)₄(μ-dppa)₂] (R = Bu^t1, Ph 2) with a double dppa-bridged system. However, the reactions with 2 equiv. of dppa only give mixtures of 1 or 2 and the expected cis-[Pt(CCR)₂(dppa-κP)₂] (R = Bu^t3, Ph 4). The analogous reactions using cis- or trans-[Pt(C₆F₅)₂(tht)₂] (tht = tetrahydrothiophene) as precursors afford, in 1 ∶ 1 molar ratio, the homologous pentafluorophenyl–bis(μ-dppa) diplatinum species [Pt₂(C₆F₅)₄(μ-dppa)₂] 5 or the polymer trans-[Pt(C₆F₅)₂(μ-dppa)]_n7 and, in 1 ∶ 2 molar ratio, the mononuclear cis- or trans-[Pt(C₆F₅)₂(dppa-κP)₂] (6, 8) derivatives. The molecular structure of 5 has been confirmed by X-ray diffraction. Furthermore, [Pt₂(CCR)₄(μ-dppa)₂] 1 and 2 react with 2 equiv. of cis-[Pt(C₆F₅)₂(thf)₂] to afford the tetranuclear bis(μ-alkynyl)bis(μ-dppa) platinum complexes [(C₆F₅)₂Pt(μ-CCR)₂Pt(μ-dppa)]₂ (R = Bu^t9, Ph 10). However, a mixture of 9/10 and [(RCC)₂Pt(μ-dppa)₂Pt(μ-CCR)₂Pt(C₆F₅)₂] (R = Bu^t11, Ph 12) is observed if the reactions are carried out in 1 ∶ 1 molar ratios. Finally, dinuclear P-bonded mono μ-dppa complexes of type Q₂[cis-{Pt(C₆F₅)₂X}₂(μ-dppa)] [Q = NBu₄, X = C₆F₅13, X = Cl 14; Q = PMePh₃, X = CCPh 15 (X-ray)] have also been prepared starting from the appropriate precursors and dppa.