Reactions of the Cobaltaborane 2,4-{(η5-C5Me5)Co}2B3H7with Metal Fragments. Synthesis and Characterization ofnido-1-{(η5-C5Me5)Co}-2-{(CO)3Fe}B3H7andarachno-(η5-C5Me5)(CO)CoB3H7

The reactions of nido -2,4-(Cp*Co) 2 B 3 H 7, 1, Cp* = (η 5 -C 5 Me 5 ), with Fe 2 (CO) 9 and Co 2 (CO) 8 generate seven skeletal electron pair (sep) nido -1-{Cp*Co}-2-((CO) 3 Fe)B 3 H 7, 2, by metal fragment substitution and seven sep arachno -Cp*(CO)CoB 3 H 7, 3, by metal fragment degradation. Both compounds are characterized spectroscopically in solution and with single-crystal X-ray diffraction in the solid state. On the basis of the results and related chemistry, the suggested reaction pathway involves M(CO) 4, M = Fe and Co, coordination to a Co−H−B edge of 1 followed by loss of Cp*Co(CO) which leads to 2 . We postulate that the cobalt analogue of 2, which would be an odd-electron species, readily loses a cobalt carbonyl fragment to form 3 .