Bimetallic systems. Part 4. Synthesis and characterisation of mixed copper(I)–, silver(I)–, or gold(I)–platinum(II) acetylide complexes containing bridging Ph2PCH2PPh2

Abstract

The bis(monodentate dppm)diacetylide complexes of type trans-[Pt(CCR)₂(dppm-P)₂](dppm = Ph₂PCH₂PPh₂; R = Ph, p-tolyl, Me, etc.) react with silver nitrate or silver hexafluorophosphate to give mixed platinum–silver salts of the type [(RCC)₂Pt(µ-dppm)₂Ag]X (X = NO₃^– or PF₆^–) or with [{AgX(PPh₃)}₄](X = Cl or I) to give neutral platinum–silver complexes, [(RCC)₂Pt(µ-dppm)₂-AgX](X = Cl or I), in excellent yield. The salts and neutral complexes can be interconverted, e.g. the nitrate salt with NaI gives the neutral platinum–silver iodide complex and when the neutral platinum–silver chloride complex [(PhCC)₂Pt(µ-dppm)₂AgCl] is treated with [NH₄][PF₆] in acetone the corresponding [PF₆]^– salt is formed. A more convenient method of synthesis of the complex [(PhCC)₂Pt(µ-dppm)₂AgX] is to treat [Pt(dppm-PP′)₂]X₂(X = Cl or I) with two equivalents of AgO₂CMe + PhCCH. Treatment of [Pt(dppm-PP′)₂]X₂ with one equivalent of AgO₂CMe + RCCH gives platinum–silver monoacetylides of type [(RCC)ClPt(µ-dppm)₂AgCl](R = Ph, p-tolyl, Me, CH₂CH₂Ph, or CMeCH₂). In ‘one-pot’ reactions PtCl₂(or K₂[PtCl₄]) was treated with two equivalents of dppm followed by one equivalent of AgO₂CMe + PhCCH to give the complex [(PhCC)ClPt(µ-dppm)₂AgCl] in 71% overall yield. This chloro-complex, when treated with LiBr or NaI in dichloromethane–acetone, gave the corresponding bromo- or iodo-complexes [(PhCC)XPt-(µ-dppm)₂AgX](X = Br or I) in ca. 90% yields. Treatment of [Pt(CCC₆H₄Me-P)₂(dppm-p)₂] with [AuCl(PPh₃)] gave the platinum–gold complex salt [(p-MeC₆H₄CC)₂Pt(µ-dppm)₂Au]Cl. Treatment of [Pt(dppm-PP′)₂]Cl₂ with Li[Cu(CCPh)₂] gives [(PhCC)₂Pt(µ-dppm)₂CuCl], which in acetone solution + Na[BPh₄] gives the corresponding salt [(PhCC)₂Pt(µ-dppm)₂Cu][BPh₄]. All of the complexes were characterised by microanalysis, solution conductivity measurements, i.r. spectroscopy, and particularly ³¹P-{¹H} and ¹H-{³¹P} n.m.r. spectroscopy. The variable-temperature ¹H-{³¹P} and ³¹P-{¹H} n.m.r. spectra of the complexes are discussed.