Distinct Palladium(II) Carbene Complexes Supportedby Six-Membered 13-Disubstituted Permidin-2-ylidene Six-MemberedN-Heterocyclic Carbenes

摘要

The first synthesis, isolation, and characterization of permidin-2-ylidene complexes of Pd(II) is reported with entry resulting from either a direct reaction with isolable six-membered N-heterocyclic carbene or from the enetetramine, arising from dimerization of the carbene. Furthermore, a simplified method to prepare N,N′-disubstituted perimidinium bromide salts, precursors to 1,3-disubstituted perimidin-2-ylidene, was achieved using ammonium bromide as a source of weak acid. Through synthesis and nuclear magnetic resonance spectroscopic analysis of a carbene-phosphinidine adduct, an interrogation of the fundamental π-bonding ability of 1,3-diisopropylperimidin-2-ylidene revealed this interaction to be weak and of a similar order to unsaturated imidazol-2-ylidenes.