Synthesis of palladium and platinum complexes with phosphine-functionalized benzimidazolin-2-ylidene ligands

Phosphine-functionalized benzimidazolium salts of the type N-(2-phosphinoethyl)-N'- alkylbenzimidazolium chloride ( 4, alkyl=ethyl; 5, alkyl=n-propyl; 6, alkyl=n- butyl) and N, N'- bis(2- phosphinoethyl)-5,6-dimethylbenzimidazolium chloride ( 9) have been prepared. The reaction of 4-6 with silver oxide followed by a carbene transfer reaction from silver to palladium or platinum gave complexes of the type cis-[M(PCNHC)Cl-2] 13-18 (M) Pd, Pt; PCNHC) N-( 2-phosphinoethyl)-N'-alkylbenzimidazolin-2-ylidene). The pincer-type complexes [ M((PCP)-P-NHC) Cl] Cl (M) Pd (20), Pt ( 21); (PCP)-P-NHC) N, N'-bis(2-phosphinoethyl) benzimidazolin-2-ylidene) with a diphosphine-functionalized carbene ligand have been synthesized by carbene transfer from the corresponding silver complex [Ag((PCP)-P-NHC)Cl] (19) to [PdCl2(cod)] or [PtCl2-(PhCN)(2)]. The metathesis reaction of 20 with silver tetrafluoroborate in pyridine produced [Pd((PCP)-P-NHC)-py](BF4)(2) ( 22). Compounds 13, 15, and 22 center dot 0.5MeOH have been characterized by X- ray diffraction. Hecktype coupling reactions of several aryl halides with styrene and n-butyl acrylate have been studied with the palladium complexes containing phosphine-functionalized carbene ligands as catalysts.