KAIST, Electrochemistry Jeong-Wook Hwang, Jae-Hak Kim, Hangil Lee, Hochun Lee, Sehun Kim, Juhyoun Kwak, and Youngkyu Do, "Novel Families of Three-Component Reversible Redox Cycles Involving Cage Deformation via Intramolecular Redox Reaction: Tetrathiolate-Bridged Dinuclear Molybda- and Tungstacarboranes," J. Am. Chem. Soc., 123 (37), 9054 - 9063 (2001.09.19.)

Abstract
The synthesis and structural analysis of two novel families of three-component reversible redox cycles [(C2B9H11)M(m-SPh)2]2nPPNn (M = Mo, n = 2-, 2; 1-, 3; 0, 4; and M = W, n = 2-, 6; 1-, 7; 0, 8), where the cleavage and re-formation of the carborane cage C-C bond is observed during the redox reaction, are reported. Electronic saturation of the metal center (18e center) and the lack of bulky substituents on the carborane cage suggest that the deformed carborane cages in 2·PPN2, 6·PPN2, and 7·PPN invoke a new kind of deformed cage ("semicloso" framework). The XPS results show that the unprecedented competition for electron density between the metal center and the carborane cage is involved in the cleavage and formation of the carborane C-C bond.