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 Rh-10(C)(2) frame, with variable numbers of CO ligands, AuPPh3 moieties, and anionic charge: [Rh-10(C)(2)(CO)(x)(AuPPh3)(y)](n-) in (x = 18, 20; y = 4, 5, 6; n = 0, 1, 2). Anions [Rh-10(C)(2)(CO)(18)(AuPPh3)(4)](-) ([2](-)) and [Rh-10(C)(2)(CO)(18)(AuPPh3)(4)](2-) ([2](2-)) have been obtained by the reduction of [Rh-10(C)(2)(CO)(18)(AuPPh3)(4)] (2) under N-2, while [Rh-10(C)(2)(CO)(18)(AuPPh3)(5)](-) ([3](-)) was obtained from [Rhio(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-). [Rh-10(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.