The syntheses, resolution, electronic structures, and stereochemistry of mixed-ligand complexes of cobalt(II1) with the dianion of oxalic acid and ammonia, ethylenediamine (en), 1,3-diaminopropane (tn), triethylenetetramine (trien), 3,T-diaza-1,Q-diaminononane (2,3,2-tet), and 4,7-diaza-l,lO-diaminodecane (3,2,3-tet) are reported. The instability of cobalt(II1) complexes with 4,8-diaza-l,ll-diaminoundecane (3,3,3-tet) indicates that the complexes Co(KHs):ox+, Co(en)zox+, CO-(tn)lox+, a-cis-Co(trien)ox+, p-cis-Co(trien)ox+, P-cis-Co(2,3,2-tet)oxL, and a-cis-Co(3,2,3-tet)ox+ comprise the complete series of oxalatotetramine complexes with unsubstituted amines.