LINKED AND MERCURY-BRIDGED NIDO-CARBORANES - HIGH-YIELD SYNTHESIS OF MU,MU'-[(CH3)2C2B4H5]2HG, CONVERSION TO 5,5'-[(CH3)2C2B4H5]2, CLEAVAGE, AND OXIDATIVE ADDITION OF BENZENE - SYNTHESIS OF MU,MU'-(B5H8)2HG

The nido-carborane anion [2, 3-(CH3)2C2B4H5]- reacts readily with anhydrous HgCl2 in THF at room temperature, producing the bis(carboranyl)mercury(II) complex μ, μ‘-[(CH3)2C2B4H5]2Hg in which the metal is bound to two carborane ligands via B-Hg-B three-center, two-electron bridge bonds. On heating at 180 °C in benzene, this compound quantitatively expels free mercury and forms the B-B-linked nido-carborane 5, 5‘-[(CH3)2C2B4H5]2 as a single pure isomer. Air oxidation of the linked carborane in benzene solution results in cleavage of the carborane-carborane B-B bond and oxidative addition of benzene to give 4-C6H5-2, 3-(CH3)2C2B4H5, an apparently air-stable derivative of nido-2, 3-C2B4H8. Similar treatment of the linked carborane in C6D6 gives the corresponding hexadeuterated carborane product. The reaction of B5Hg- ion with HgCl2 in THF produces μ, μ‘-(B5H8)2Hg, a stable solid in which mercury is evidently bridge bonded to two pentaborane ligands. © 1979, American Chemical Society. All rights reserved.