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Probing Stepwise Reaction of NNP–Ligand Copper(I) Complex with Elemental Sulfur by Using N-Heterocyclic Carbene as a Trapper

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journal contribution
posted on 01.08.2011 by Gengwen Tan, Hongping Zhu
The dinuclear NNP–ligand copper(I) complex [o-NCH(C4H3N)–PPh2C6H4]2Cu2 (1) has been synthesized by the reaction of (CuMes)4 (Mes = 2,4,6-Me3C6H2) with N-((1H-pyrrol-2-yl)-methylene)-2-(diphenylphosphino)benzenamine under an elimination of MesH. Further reaction of 1 with an excess of S8 produced a mononuclear Cu(II) complex [o-NCH(C4H3N)–P(S)Ph2C6H4]2Cu (5) and CuS. CuS was identified by Raman spectroscopy and 1 and 5 were clearly confirmed by X-ray crystallography. The N-heterocyclic carbene was employed to react with 1 to give a mononuclear [o-NCH(C4H3N)–PPh2C6H4]Cu{C[N(iPr)CMe]2} (2). The reactions of 2 were carried out with 1/8, 2/8, and 5/8 equiv of S8, leading to compounds [o-NCH(C4H3N)–P(S)Ph2C6H4]Cu{C[N(iPr)CMe]2} (3), [o-NCH(C4H3N)–P(S)Ph2C6H4]Cu (4), and 5 respectively, in which CuS was generated in the third reaction and SC[N(iPr)CMe]2 in the latter two reactions. The clean confirmation of 24 demonstrates a stepwise reaction process of 1 with S8 to 5 and CuS and the N-heterocyclic carbene acts well as a trapping agent.