Bimetallic systems. Part 8. Heterobimetallic di-isonitrile or isonitrile–carbonyl complexes of rhodium or iridium bridged to silver or gold by Ph2PCH2PPh2

Abstract

Treatment of [M₂(CNBu^t)₄(µ-dppm)₂]Cl₂(M = Rh or Ir, dppm = Ph₂PCH₂PPh₂) with dppm gave labile systems at 20 °C. ³¹P-{¹H} N.m.r. spectroscopy at –60 °C showed complete conversion to the tris-monodentate dppm complexes [M(CNBu^t)₂(dppm-P)₃]Cl. Treatment of [Rh₂(CNBu^t)₄(µ-dppm)₂][PF₆]₂ with two moles of dppm followed by AgNO₃ gave the mixed rhodium–silver complexes [(Bu^tNC)₂Rh(µ-dppm)₂Ag][PF₆][NO₃]. Salts with other counter ions, viz. Cl^–, were also prepared. A rhodium–gold complex [(Bu^tNC)₂Rh(µ-dppm)₂Au]Cl₂ was prepared using [AuCl(PPh₃)] and a [Rh₂(CNBu^t)₄(µ-dppm)₂]Cl₂–dppm mixture. Treatment of [{Ir(C₈H₁₄)₂Cl}₂] with four mol equivalents of dppm, six of Bu^tNC, and two of [AuCl(PPh₃)] gave the fluxional molecule [(Bu^tNC)₃Ir(µ-dppm)₂Au]Cl₂ which showed a particularly well defined AA′XX′³¹P-{¹H} n.m.r. pattern (18 of the theoretical 20 lines), and which was analysed. Treatment of [Ir(CO)(dppm-PP′)₂]Cl with [AgCl(CNBu^t)] gave the mixed iridium–silver complex [(OC)(Bu^tNC)Ir(µ-dppm)₂AgCl]Cl in good yield. The MeNC and p-MeC₆H₄NC analogues were prepared similarly as were the corresponding rhodium–silver complexes, [(OC)(RNC)Rh(µ-dppm)₂AgCl]Cl(R = Bu^t or p-tolyl).