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

2011-08-01T00:00:00Z (GMT) by Gengwen Tan Hongping Zhu
The dinuclear NNP–ligand copper(I) complex [<i>o</i>-NCH(C<sub>4</sub>H<sub>3</sub>N)–PPh<sub>2</sub>C<sub>6</sub>H<sub>4</sub>]<sub>2</sub>Cu<sub>2</sub> (<b>1</b>) has been synthesized by the reaction of (CuMes)<sub>4</sub> (Mes = 2,4,6-Me<sub>3</sub>C<sub>6</sub>H<sub>2</sub>) with <i>N</i>-((1<i>H</i>-pyrrol-2-yl)-methylene)-2-(diphenylphosphino)benzenamine under an elimination of MesH. Further reaction of <b>1</b> with an excess of S<sub>8</sub> produced a mononuclear Cu(II) complex [<i>o</i>-NCH(C<sub>4</sub>H<sub>3</sub>N)–P(S)Ph<sub>2</sub>C<sub>6</sub>H<sub>4</sub>]<sub>2</sub>Cu (<b>5</b>) and CuS. CuS was identified by Raman spectroscopy and <b>1</b> and <b>5</b> were clearly confirmed by X-ray crystallography. The <i>N</i>-heterocyclic carbene was employed to react with <b>1</b> to give a mononuclear [<i>o</i>-NCH(C<sub>4</sub>H<sub>3</sub>N)–PPh<sub>2</sub>C<sub>6</sub>H<sub>4</sub>]Cu{C[N(<i>i</i>Pr)CMe]<sub>2</sub>} (<b>2</b>). The reactions of <b>2</b> were carried out with <sup>1</sup>/<sub>8</sub>, <sup>2</sup>/<sub>8</sub>, and <sup>5</sup>/<sub>8</sub> equiv of S<sub>8</sub>, leading to compounds [<i>o</i>-NCH(C<sub>4</sub>H<sub>3</sub>N)–P(S)Ph<sub>2</sub>C<sub>6</sub>H<sub>4</sub>]Cu{C[N(<i>i</i>Pr)CMe]<sub>2</sub>} (<b>3</b>), [<i>o</i>-NCH(C<sub>4</sub>H<sub>3</sub>N)–P(S)Ph<sub>2</sub>C<sub>6</sub>H<sub>4</sub>]Cu (<b>4</b>), and <b>5</b> respectively, in which CuS was generated in the third reaction and SC[N(<i>i</i>Pr)CMe]<sub>2</sub> in the latter two reactions. The clean confirmation of <b>2</b>–<b>4</b> demonstrates a stepwise reaction process of <b>1</b> with S<sub>8</sub> to <b>5</b> and CuS and the <i>N</i>-heterocyclic carbene acts well as a trapping agent.