MIXED COBALTACARBORANES INCORPORATING ETA(5)-PYRROLYL AND DICARBOLLIDE LIGANDS - SYNTHETIC ROUTES, STRUCTURES, AND MECHANISTIC IMPLICATIONS

Mixed cobaltacarboranes [(eta(5)-NC4H4)Co(7-R-8-R'-7,8-C2B9H9)] contai ning eta(5)-pyrrolyl and dicarbollide ligands have been synthesized. R eaction of [N(CH3)(4)][7-R-8-C4H4N-(CH2)(3)-7,8-C2B9H10] (R = CH3, C6H 5) with K(t-BuO) and CoCl2 in dimethoxyethane leads to two complexes w ith the formulae [(eta(5)-NC4H4)Co(7-R-8-C4H9-7,8-C2B9H9)] and [(eta(5 )-NC4H4)Co(7-R-8-C3H5-7,8-C2B9H9)] (R = CH3, C6H5). The 8-C4H9 and 8-C 3H5 groups are produced as a result of the cleavage of the spacer join ing the pyrrolyl and carborane moieties in the original ligand. The [N (CH3)(4)](+) ion is necessary to produce the 8-C4H9 substituent. An al ternative and more efficient route to [(eta(5)-NC4H4)Co(7-R-8-C3H5-7,8 -C2B9H9)] (R = CH3, C6H5) involves the reaction of 1-Cl(CH2)(3)-2-R-1, 2-C2B10H10 (R = CH3, C6H5) with K(NC4H4) and CoCl2 in dimethoxyethane. This last route can also be utilized to produce the simple [(eta(5)-N C4H4)Co(7-R-8-R'-7,8-C2B9H9)] compounds starting from closo-1-R-2-R'-1 ,2-C2B10H10 compounds. The structures of those species have been prove n by X-ray structural analyses of [(eta(5)-NC4H4)Co(7-CH3-8-C4H9-7,8-C 2B9H9)] and [(eta(5)-NC4H4)Co(7-C6H5-8-C3H5-7,8-C2B9H9)].