SYNTHESES, REACTIVITY AND COMPLEXATION PROPERTIES OF NIDO-2,3,5-TRICARBAHEXABORANES

By double hydroboration of 1,3-dihydro-1,3-diborafulvenes 2 or 4,5-diisopropylidene-1,3-diborolanes 3 with (Et2BH)2 and subsequent loss of triethylborane derivatives 1 of 2,3,5-tricarbahexaborane are formed under mild conditions. The stability of the nido-carboranes 1 depends on the substituents in the basal positions. After deprotonation, the tricarbahexaboranate ion (1 - H)- functions as a cyclopentadienyl analogue (C5H5)-, and its reaction with allylnickel bromide dimer gives the allylnickel complexes 8a, b. Reaction of octacarbonyl dicobalt with 1b yields the dicarbonylcobalt complex 10b. Treatment of 1e with [(C5H5)Ni(CO)]2 results in the formation of the di-nuclear carbonyl-bridged complex 12e.