Four-Carbon Carboranes. Synthesis of (CH3)4C4B8H8and Its Metallocarborane Derivatives.

摘要

The decomposition of the metallocarboranes ((CH3)2C2B4H4)2CoH or ((CH3)2C2B4H4)2FeH2yields (CH3)4C4B8H8 (I),an air-stable crystalline solid. The evidence indicates that I exists as a single isomer (A) in the solid state but rearranges in a variety of solvents to a second isomer (B). On removal of solvent the mixture reverts entirely to A. Both isomers are non-fluxional below 20degrees,but at 40degrees B exhibits fluxional behavior which renders the methyl groups equivalent. 11B and 1H nmr spectra suggest an open structure for A and a compact pseudo-icosahedral geometry for B. I reacts with hexacarbonyls of molybdenum and tungsten to yield neutral (CO)3M(CH3)4C4B8H8species,the first 4-carbon metallocarboranes and the first containing a neutral carborane ligand. (Modified author abstract)