In the exploration of sulfur-delivery reagents useful for synthesizing models of the tetracopper-sulfide cluster of nitrous oxide reductase, reactions of Ph3Sb=S with Cu(I) complexes of N,N,N′,N′-tetramethyl- 2R,3-R-cyclohexanediamine (TMCHD) and 1,4,7-trialkyltriazacyclononanes (R 3tacn; R = Me, Et, iPr) were studied. Treatment of [(R 3tacn)Cu(NCCH3)]SbF6 (R = Me, Et, or iPr) with 1 equiv of S=SbPh3 in CH2Cl2 yielded adducts [(R3tacn)Cu(S=SbPh3)]SbF6 (1-3), which were fully characterized, including by X-ray crystallography. The adducts slowly decayed to [(R3tacn)2Cu2(μ- η2:η2-S2)]2+ species (4-6) and SbPh3, or more quickly in the presence of additional [(R 3tacn)Cu(NCCH3)]SbF6 to 4-6 and [(R 3tacn)Cu(SbPh3)]SbF6 (7-9). The results of mechanistic studies of the latter process were consistent with rapid intermolecular exchange of S=SbPh3 between 1-3 and added [(R 3tacn)Cu(NCCH3)]SbF6, followed by conversion to product via a dicopper intermediate formed in a rapid pre-equilibrium step. Key evidence supporting this step came from the observation of saturation behavior in a plot of the initial rate of loss of 1 versus the initial concentration of [(Me3tacn)Cu(NCCH3)]SbF6. Also, treatment of [(TMCHD)Cu(CH3CN)]PF6 with S=SbPh3 led to the known tricopper cluster [(TMCHD)3Cu3(μ3-S) 2](PF6)3 in good yield (79%), a synthetic procedure superior to that previously reported.