Reaction of copper(I) iodide with tris (N,N- dipropyl -and N, N- diisopropyl-dithiocarbamato )cobalt(III), [Co(S2CNR2)3 = Co( dtc )3](R = Pr or Pri ), yields 1:1 adducts which have been characterized by single-crystal X-ray structure determination. Crystals of the propyl species are monoclinic, P21/c, a 13.722(7), b 16.854(7), c 16.787(8)?, ߠ121.66(3)ଠR was 0.056 for No 2834 'observed' reflections. The isopropyl derivative is orthorhombic, Ccca , a 33.93 (1), b 13.616(8), c 14.574(5)?; R was 0.075 for No 726. Each adduct is dimeric Co( dtc )3[Co( dtc )3]; the propyl derivative has crystallographically imposed i symmetry, whereas the isopropyl adduct has quasi-222 symmetry. Thus, the chiralities of the pair of Co( dtc )3 moieties in the dipropyl adduct are opposite, whereas in the isopropyl adduct they are the same.