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

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 2–4 demonstrates a stepwise reaction process of 1 with S8 to 5 and CuS and the N-heterocyclic carbene acts well as a trapping agent.

二核NNP-配体铜(I)复合物[o-NCH(C4H3N)–PPh2C6H4]2Cu2 (1) 通过(CuMes)4 (Mes = 2,4,6-三甲基苯)与N-((1H-吡咯-2-基)-亚甲基)-2-(二苯基膦基)苯胺的反应，在消除MesH的条件下成功合成。进一步将1与过量的S8反应，生成单核Cu(II)复合物[o-NCH(C4H3N)–P(S)Ph2C6H4]2Cu (5) 和CuS。通过拉曼光谱确定了CuS，而1和5则通过X射线晶体学得到了明确的确认。N-杂环卡宾被用于与1反应，得到单核[o-NCH(C4H3N)–PPh2C6H4]Cu{C[N(iPr)CMe]2} (2)。将2与1/8、2/8和5/8当量的S8进行反应，分别得到化合物[o-NCH(C4H3N)–P(S)Ph2C6H4]Cu{C[N(iPr)CMe]2} (3)、[o-NCH(C4H3N)–P(S)Ph2C6H4]Cu (4)和5，其中第三反应生成了CuS，而后两种反应中则生成了SC[N(iPr)CMe]2。2–4的纯净确认展现了1与S8逐步反应至5和CuS的过程，同时N-杂环卡宾作为一种有效的捕获剂发挥了显著作用。