Bimetallic systems. Part 17. Synthesis of Group 6 metal(0)–copper(I)–silver(I), or –gold(I) complexes with two Ph2PCH2PPh2(dppm) bridging ligands: crystal structure of [(OC)2W(µ-CO)(µ-dppm)2(µ-Cl)Cu]·CH2Cl2

Abstract

Treatment of fac- or mer-[M (CO)₃(dppm-PP′)(dppm-P)](M = Cr, Mo, or W; dppm = Ph₂PCH₂PPh₂) with Cu^I, Ag^I, or Au^I compounds sometimes induced ring-opening to give heterobimetallic complexes, but in other cases rapid redox reactions, or more complicated processes, occurred. Treatment of mer-[M(CO)₃(dppm-PP′)(dppm-P)](M = Cr, Mo, or W) with CuX (X = Cl or I) gave [(OC)₂M (µ-CO)(µ–dppm)₂(µ-X)Cu] in moderate yields, whereas treatment of fac-[M(CO)₃(dppm-PP′)(dppm-P)](M = Mo or W) with CuX gave only Cu^I-dppm species. fac- or mer-[M(CO)₃(dppm-PP′)(dppm-P)] were oxidised by AgNO₃, but in general reacted with [Ag₄Cl₄(PPh₃)₄] to give M–Ag complexes with one bridging dppm. However, treatment of mer-[Mo(CO)₃(dppm-PP′)(dppm-P)] with [Ag₄Cl₄(PPh₃)₄] gave an unstable complex [(OC)₃Mo(µ-dppm)₂ AgCl], the ³¹P-{¹H} n.m.r. spectra of which varied with temperature. Treatment of fac-or mer-[M(CO)₃(dppm-PP′)(dppm-P)] with [Ag(PPh₃)(CN)] gave stable, heterobimetallic, complexes of the type [(OC)₃M(µ-dppm)₂Ag(CN)](M = Cr, Mo, or W). Reaction between mer-[M(CO)₃(dppm-PP′)(dppm-P)](M = Mo or W) and [Au(PPh₃)Cl] gave [(OC)₃M (µ-dppm)₂AuCl], whereas a complex mixture of unidentified products was formed on treating fac-[M(CO)₃(dppm-PP′)(dppm-P)] with [Au(PPh₃)Cl]. The molecular structure of [(OC)₂W(µ-CO)(µ-dppm)₂(µ-Cl)Cu]·CH₂Cl₂ was determined from a monoclinic crystal of space group P2₁/c, with a= 1 076.0(2), b= 2 513.2(4), c= 2 067.5(3) pm, β= 112.62(1)°, and Z= 4; final R factor 0.0359 for 6 138 observed reflections. The structure shows that the two metal centres [W–Cu 275.9(4) pm] are almost symmetrically bridged by chlorine [W–Cl 259.2(5), Cu–Cl 255.3(5) pm] and semibridged by CO.