Research on Synthesis, Structure, and Catalytic Performance of Tetranuclear Copper(I) Clusters Supported by 2-Mercaptobenz-zole-Type Ligands

Tetrahedral copper(I) clusters [Cu₄(MBIZ)₄(PPh₃)₂] (<b>2</b>), [Cu₄(MBOZ)₄(PPh₃)₄] (<b>6</b>) (MBIZ = 2-mercaptobenzimidazole, MBOZ = 2-mercaptobenzoxazole) were prepared by regulation of the copper-thiolate clusters [Cu₆(MBIZ)₆] (<b>1</b>) and [Cu₈(MBOZ)₈I]^- (<b>5</b>) with PPh₃. With the presence of iodide anion, the regulation provided the iodide-containing clusters [Cu^I₄(MBIZ)₃(PPh₃)₃I] (<b>3</b>) and [Cu^I₄(MBOZ)₃(PPh₃)₃I] (<b>7</b>). The cyclic voltammogram of <b>3</b> in MeCN (0.1 M ⁿBu₄NPF₆, 298 K) at a scan rate of 100 mV s^-1 shows two oxidation processes at E_p^a = +0.11 and +0.45 V with return waves observed at E_p^c = +0.25 V (vs. Fc⁺/Fc). Complex <b>3</b> has a higher capability to lose and gain electrons in the redox processes than complexes <b>2</b>, <b>4</b>, <b>4</b>', <b>6,</b> and <b>7</b>. Its thermal stability was confirmed by thermogravimetric analysis. The catalytic performance of <b>3</b> was demonstrated by the catalytic transformation of iodobenzenes to benzonitriles using AIBN as the cyanide source. The nitrile products show potential applications in the preparation of 1,3,5-triazine compounds for organic fluorescence materials.