Synthesis, reactivity, electrochemical behavior, and crystal structure of a family of multivalent metal carbido-carbonyl clusters based on the rh(10)(c)(2)au(4-6) 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, AuPPh(3) moieties, and anionic charge: Rh(10)(C)(2)(CO)(x)(AuPPh(3))(y)](n-) (x = 18, 20; y = 4, 5, 6; n = 0, 1, 2). Anions Rh(10)(C)(2)(CO)(18)(AuPPh(3))(4)](-) (2](-)) and Rh(10)(C)(2)(CO)(18)(AuPPh(3))(4)](2-) (2](2-)) have been obtained by the reduction of Rh(10)(C)(2)(CO)(18)(AuPPh(3))(4)] (2) under N(2), while Rh(10)(C)(2)(CO)(18)(AuPPh(3))(5)](-) (3](-)) was obtained from Rh(10)(C)(2)(CO)(20)(AuPPh(3))(4)] (1) by reduction under a CO atmosphere. 3](-) can be better obtained by the addition of AuPPh(3)Cl to 2](2-). Rh(10)(C)(2)(CO)(18)(AuPPh(3))(6)] (4) is obtained from 3](-) and 2 as well by the reduction and subsequent addition of AuPPh(3)Cl. The molecular structures of 2](2-) (NBu(4)](+) salt), 3](-) (NMe(4)](+) 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.