Reactions of Ph3Sb═S with Copper(I) Complexes Supported by N-Donor Ligands: Formation of Stable Adducts and S-Transfer Reactivity

摘要

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, 3R-cyclohexanediamine (TMCHD) and 1, 4, 7-trialkyltriazacyclononanes (R3tacn; R = Me, Et, iPr) were studied. Treatment of [(R_3tacn)Cu(NCCH_3)]SbF_6 (R = Me, Et, or iPr) with 1 equiv of S═SbPh3 in CH2Cl2 yielded adducts [(R3tacn)Cu(S═SbPh_3)]SbF6 (1?3), which were fully characterized, including by X-ray crystallography. The adducts slowly decayed to [(R_3tacn)_2Cu_2(μ-η2:η2-S2)]2+ species (4?6) and SbPh3, or more quickly in the presence of additional [(R3tacn)Cu(NCCH_3)]SbF_6 to 4?6 and [(R3tacn)Cu(SbPh_3)]SbF_6 (7?9). The results of mechanistic studies of the latter process were consistent with rapid intermolecular exchange of S═SbPh_3 between 1?3 and added [(R3tacn)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 (Brown, E. C.; York, J. T.; Antholine, W. E.; Ruiz, E.; Alvarez, S.; Tolman, W. B. J. Am. Chem. Soc.2005, 127, 13752?13753).