Reactions between 7-L-nido-7,8,9-C 3 B 8 H 1 0 compounds (where L = Bu t NH 2 and Me 2 NH) and [NMe 3 H] + [7,8-C 2 B 9 H 1 2 ] - in the presence of NaH, followed by the addition of anhydrous CoCl 2 and prolonged heating in diglyme at reflux, resulted in the isolation of mixed-ligand 12-vertex cobaltacarboranes [closo-(9-R 2 N-1,7,9-C 3 B 8 H 1 0 )-commo-2,(3')-Co- (1',2'-C 2 B 9 H 1 1 )] (where R = H or Me). These represent neutral, crossover complexes between metallatricarbollides and metalladicarbollides and contain amino groups attached to p-positions with respect to the metal centre.