Synthesis and reactions of [(OC)2Re(µ-dppm)2(µ-Cl)2Rh(η2-C2H4)](dppm = Ph2PCH2PPh2): crystal structure of the 1 : 2 chlorobenzene solvate

Abstract

Treatment of [ReCl(CO)₅] with Ph₂PCH₂PPh₂(dppm) gives mer,cis-[ReCl(CO)₂(dppm-PP′)-(dppm-P)](1). The uncomplexed phosphorus of (1) is readily quaternized by [OMe₃][BF₄] to give mer,cis-[ReCl(CO)₂(dppm-PP′)(Ph₂PCH₂PPh₂Me)]BF₄(2). Treatment of complex (1) with [Rh₂Cl₂(C₂H₄)₄] gives [(OC)₂Re(µ-dppm)₂(µ-Cl)₂Rh(η²-C₂H₄)](3). The ethylene ligand in (3) is readily displaced by allene to give [(OC)₂Re(µ-dppm)₂(µ-Cl)₂Rh(η²-C₃H₄)](4). When complex (3) is treated with dihydrogen [(OC)₂Re(µ-dppm)₂(µ-Cl)(µ-H)RhH(Cl)](5) is formed; with CO [Cl(OC)Re(µ-dppm)₂(µ-Cl)(µ-CO)Rh(CO)](6) is initially formed but this reacts further to give [(OC)₃Re(µ-dppm)₂(µ-Cl)Rh(CO)]Cl (7a). The complexes (6) and (7a) were more readily prepared by treating (1) with [Rh₂Cl₂(CO)₄]. The chloride salt (7a) was converted into the corresponding PF₆(7b) and BPh₄(7c) salts. We also report the corresponding iridium salt [(OC)₃Re(µ-dppm)₂(µ-Cl)Ir(CO)]PF₆(8). N.m.r. and i.r. data are given. Crystals of (3) are monoclinic, space group P2₁/n(=P2₁/c, no.14) with a= 1 027.5(8), b= 2 996.5(9), c= 2 142.2(5) pm, and β= 92.50(2)°; final R and R′ values 0.0485 and 0.0518, respectively for 6 816 unique reflections with I > 2.0σ(I). The crystal structure shows an η²-ethylene, terminally bound to the rhodium atom, with an unusually long carbon–carbon distance [150(2) pm].