Studies of the synthesis and derivative chemistry of icosahedral carboranes

Abstract

As part of the general study of icosahedral carborane chemistry a comprehensive literature survey is presented with references. Investigations of the preparative routes to ortho-carborane, 1-methyl-o-carborane and some carborane polymers showed that improvements on existing literature methods could be made. In the synthesis of possible carborane-polymer precursors, several coupled carborane systems were investigated. These included C-C',B-B' direct cage coupling reactions and coupling via short alkyl chains. Reactions of MeƟLi (Ɵ= -CB(_10)HC-) with boron chlorides produced the previously unreported boron coupled carboranes (MeƟ)(_2)BR, (R=C1,OH, Ph) and MeƟBPh(_2). Three carborane cages could not be bonded to a singleboron atom. The previously unreported di-(3,3'-o-carboranyl)-N,N-r 12-piperazine was prepared from the [HƟH](^2-) anion. Studies were made of the reaction of MeƟLi with ICN and (CN)(_2). An attempted ortho-metallation reaction with SnCl(_4) MeƟLi and PhCN yielded an interesting dicyclic tin adduct, SnCl(_4). [(PhCN)(_3)](_2). The reactions of C(_2)B(_9)H(_11)(^2-) with tin, germanium and silicon tetrachlorides produced a new class of dicarboranyl metal "sandwich" compounds for which a novel tilted cage structure was proposed. Zinc metallocarboranes could not be synthesised. Hot atom chemistry was employed in attempts to prepare main group metallocarboranes by polyhedral expansion.