Synthesis, reactivity, electrochemical behavior, and crystal structure of a family of multivalent metal carbido–carbonyl clusters based on the Rh10(C)2Au4–6 framework

Six metal carbido−carbonyl clusters have been isolated and recognized as members of a multivalent family based on the dioctahedral Rh10(C)2 frame, with variable numbers of CO ligands, AuPPh3 moieties, and anionic charge: [Rh10(C)2(CO)x(AuPPh3)y]n− (x = 18, 20; y = 4, 5, 6; n = 0, 1, 2). Anions [Rh10(C)2(CO)18(AuPPh3)4]− ([2]−) and [Rh10(C)2(CO)18(AuPPh3)4]2− ([2]2−) have been obtained by the reduction of [Rh10(C)2(CO)18(AuPPh3)4] (2) under N2,while [Rh10(C)2(CO)18(AuPPh3)5]− ([3]−) was obtained from [Rh10(C)2(CO)20(AuPPh3)4] (1) by reduction under a CO atmosphere. [3]− can be better obtained by the addition of AuPPh3Cl to [2]2−. [Rh10(C)2(CO)18(AuPPh3)6] (4) is obtained from [3]− and 2 as well by the reduction and subsequent addition of AuPPh3Cl. The molecular structures of [2]2− ([NBu4]+ salt), [3]− ([NMe4]+ salt), and 4 have been determined by single-crystal X-ray diffraction. The redox activities of complexes 1, 2 and [3]− have been investigated by electrochemical and electron paramagnetic resonance (EPR) techniques. The data from EPR spectroscopy have been accounted for by theoretical calculations.