Copper and Silver Complexes of N-Heterocyclic Carbene-Parent Phosphinidene Adducts

The reactions of the N-heterocyclic carbene-parent phosphinidene adducts (IMes)PH (1 a) and (IDipp)PH (1 b) with one equivalent of copper(I) or silver(I) chloride afforded the monometallic complexes [{(IMes)PH}MCl] (2 a, M=Cu; 2 b, M=Ag) and [{(IDipp)PH}MCl] (3 a, M=Cu; 3 b, M=Ag). Single-crystal X-ray diffraction analyis provided evidence for a higher tendency of the (IMes)PH ligand to form polynuclear structures with bridging NHC-phosphinidene ligands in the solid state, while the larger (IDipp)PH ligand afforded mononuclear complexes. The reactions of 1 a and 1 b with two equivalents of CuCl provided evidence for the formation of the bimetallic complexes [{(NHC)PH}(CuCl)(2)] (4 a, NHC=IMes; 4 b, NHC=IDipp), but their isolation in pure form was not possible because of their considerable instability in solution.