Palladium carbene complexes as persistent radicals

A series of palladium(ii) radical carbene complexes, [PC˙(sp )P]PdI, [PC˙(sp )P]PdBr, and [PC˙(sp )P]PdCl (PC(sp )H P = bis[2-(di-iso-propylphosphino)-phenyl]methane), is described. Compound [PC˙(sp )P]PdI dimerizes to {[PC(sp )P]PdI} in the solid state, akin to the formation of Gomberg's dimer. While the bromo and the iodo derivatives could be obtained from the oxidation of [PC(sp )P]Pd(PMe ) by the respective dihalogens, a halogen transfer reaction from CH Cl was used for the formation of [PC˙(sp )P]PdCl. The halogen transfer from CH X (X = Cl, Br, I) could be used to obtain all three radical carbene palladium complexes and also allowed the isolation of [PC(CH )P]Pd(PMe ), which is the result of methylene group transfer from CH X . Compound [PC(CH )P]Pd(PMe ) was independently synthesized from [PC(CH )HP]PdCl , which contains a supporting ligand analogous to that of the radical carbene complexes but has one of the hydrogen atoms replaced by a methyl group. All three carbene radical species abstract a hydrogen from 9,10-dihydroanthracene or Bu SnH.