C18H25BBr3ClCoN6, M(r) = 670.36, orthorhombic, Cmc2(1), a = 14.575 (1), b = 10.853 (1), c = 15.731 (1) angstrom, V = 2488.4 (4) angstrom 3, Z = 4, D(x) = 1.789 g cm-3, Mo K-alpha-1, lambda = 0.70930 angstrom, mu = 55.9 cm-1, F(000) = 1316, T = 294 K, R = 0.028 for 970 reflections [I > 3-sigma-(I)]. The molecule has crystallographic mirror and approximate C3v symmetry with pseudo-tetrahedral coordination about the Co atom (mean Cl-Co-N = 122.1, N-Co-N = 94.4-degrees) and principal bond lengths: Co-Cl = 2.207 (3), Co-N = 2.039 (6) and 2.057 (9) angstrom. The Co-N distances compare well with those in another complex of the same ligand, but are about 0.08 angstrom longer than those in complexes with less bulky ligands.