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 di-octahedral 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 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 addition of AuPPh3Cl to [2]2. [Rh10(C)2(CO)18(AuPPh3)6] (4) is obtained from [3] and 2 as well, by 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 activity of complexes 1, 2 and [3] have been investigated by electrochemical and EPR techniques. The data from electron paramagnetic resonance spectroscopy have been accounted for by theoretical calculations.