We have investigated the effect of axial ligands on the ability of cobalomirnes to catalyze the generation of transferable hydrogen atoms from hydrogen gas and have learned that the active catalyst contains one and only one axial ligand. We have, for example, shown that Co(dmgBF(2))(2) coordinates only one Ph3P and that the addition of additional Ph3P (beyond 1 equiv) to solvated Co(dmgBF(2))(2) does not affect its catalytic turnover for H center dot transfer from H-2.