Copper(I) and silver(I) complexes of carbaphosphazene-anchored N-heterocyclic carbene ligands

Carbaphosphazene-anchored imidazolium salts are synthesized by treating a six-membered dichlorodiphenyldicarbaphosphazene of the formula (ClCN)2(Ph2PN) with N-Me, N-tert-Bu and N-Dipp imidazoles (Dipp = 2,6-diisopropylphenyl) in toluene. While Dipp and tert-Bu substituted imidazolium salts undergo a facile reaction with Ag2O in CH2Cl2 to form carbene complexes, [DPCP-(NHC:Bu-tAgCl)2] and [DPCP-(NHC:DippAgCl)2], no pure products are found in case of Me substituted salt. Under similar conditions, Cu2O with the N-Dipp substituted imidazolium salt gives [(DPCP-(ImidDipp)2Cl][CuICl2], a [CuICl2]− complex with the imidazolium ion as counter cation. However, a carbaphosphazene-anchored NHC complex of Cu, [DPCP-(NHC:DippCuCl)2], is also synthesized by heating a mixture of Cu2O and the N-Dipp imidazolium salt at 60 °C in acetonitrile. The complexes [DPCP-(NHC:Bu-tAgCl)2], [DPCP-(NHC:DippCuCl)2] and [(DPCP-(ImidDipp)2Cl][CuICl2] are structurally characterized. In all these compounds the imidazole rings are coplanar with the carbaphosphazene ring.