Interconversion of CN and CNH2 ligands: electrosynthesis and X-ray crystallographic structures of trans-[W(CNH2)Cl(dppe)2] and trans-[W(CNH2)Cl(dppe)2][BF4](dppe = Ph2PCH2CH2PPh2): aminocarbyne (C–NH2) or iminomethylenium (CNH2+) ligands?
Abstract
Electrochemical reduction of trans-[W(CN)Cl(dppe)2] in the prsence of phenol gives trans-[W(CNH2)Cl(dppe)2]3, which can be oxidised electrochemically or chemically to the paramagnetic cation trans-[W(CNH2)Cl(dppe)2]+4; X-ray crystallographic analyses of 3 and 4[BF4] suggest that the CNH2 group at both the 18 and 17e W-centres is best described as iminomethylenium (CNH2+); 3 and the deutero-complex trans-[W(CND2)Cl(dppe)2] reduce azobenzene with regeneration of the parent cyanide, the former giving hydrazobenzene and latter PhNDNDPh, suggesting that the CNH(D)2 complexes can behave as 2H(D) atom transfer reagents.