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

Abstract

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 mu,mu'-((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 deg. 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 B5H8 - ion with HgCl2 in THF produces mu,mu-(B5H8)2Hg, a stable solid in which mercury is evidently bridge-bonded to two pentaborane ligands. (Author)