Direct insertion of transition metals into polyhedral carboranes. Structurally novel mono-, di-, and trimetallic small cage systems

Abstract

Metallocarboranes of iron, cobalt and nickel have been prepared by the direct reaction of the small polyhedral carboranes 1,5-C2B3H5, 1,6-C2B4H6, or 2,4-C2B5H7 with organometallic and metal carbonyl reagents in the gas phase or in solution, without the use of a prior cage-opening step. Novel 6-vertex cages as well as 7-vertex species were obtained, including mono-, di-, and trimetallocarborane species. Molecular structures were assigned to the new compounds on the basis of boron-11 and proton nmr spectra. Fine structure in the carborane CH proton nmr signals exhibited by several of the cobaltacarborane species was interpreted on the basis of H-C-B-H proton-proton coupling. (Modified author abstract)