Reversible skeletal rearrangement in a carbido carbonyl cluster induced by ligand substitution. Synthesis and crystal structure of the anion [Rh12C2(CO)23(AuPPh3)]–
Abstract
The mixed-metal carbido carbonyl cluster anion [Rh12C2(CO)23(AuPPh3)]– has been obtained by reaction of [Rh12C2(CO)24]2– with [Au(PPh3)Cl]. It is an intermediate species in the previously reported reaction producing the two related clusters [Rh10C2(CO)18(AuPPh3)4] and [Rh10C2(CO)20(AuPPh3)4] and reacts with CO regenerating the starting dianion. The molecular structure of the [NEt4]+ salt has been determined by X-ray diffraction analysis [monoclinic, space group P21/n, Z= 4, a= 13.499(2), b= 32.789(3), c= 14.923(3)Å, β= 101.26(2)°]. The loss of a CO ligand and the addition of the gold fragment result in major rearrangements in the Rh12C2 cluster yielding an unprecedented layered aggregation in which three fused trigonal prisms (two containing the carbide atoms) are recognizable. The Au(PPh3)+ fragment bridges a Rh4 butterfly-shaped face of the Rh-atom skeleton. Phosphorus-31 NMR spectra at low temperature show that the solution structure is somewhat different with the gold bonded to a RhARhBRhB face. The CO ligands are distributed in such a way as to achieve a regular charge distribution among the metal atoms.