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.