The reaction of closo-[2,3,4-(eta(5)-C(5)Me(5))(3)(mu-H)(2)Co3B2H2], 1, With metal chlorides results in the formation of either closo-1-Cl-[2,3,4-(eta(5)-C(5)Me(5))(3)(mu-H)(2)Co3B2H], 2, or closo-1,5-Cl-2-[2,3,4-(eta(5)-C(5)Me(5))(3)(mu-H)(2)Co3B2], 3, depending on chlorination reagent. Hydrolysis of 1, yields closo-1-OH-[2,3,4-(eta(5)-C(5)Me(5))(3)(mu-H)(2)Co3B2H], 4. Isolated yields of 2 and 4 are modest to good, and all compounds have been characterized spectroscopically as simple substitution derivatives of 1. The substituent effects have been probed by B-11 NMR measurements and compared with those for other substituted borane and metallaborane clusters. The observation of an enhanced antipodal effect shows that 1 possesses a characteristic property of a five-atom close cage suggesting delocalized cluster bonding that includes both the boron and metal centers.