(Diphenylphosphino)alkyl-functionalized nucleophilic carbene complexes of palladium

The (diphenylphosphino)alkyl-functionalized nucleophilic heterocyclic carbene (NHC) complexes of palladium LPdX2 (L = (3-R-1)[1-Ph2P(CH2)(2)]-imidazol-2-ylidene; R-1 = 2,6-(Pr2C6H3)-C-i, 2,4,6-Me3C6H2; X = CH3 (3a,b), X = Br (4a,b)) have been synthesized by the reaction of the in situ generated functionalized NHC ligand L-a or L-b with Pd(tmed)(CH3)(2) and Pd(COD)Br-2, respectively, and structurally characterized. Interaction of 3a with H(Et2O){B[3,5-(CF3)(2)C6H2]4} and pyridine or with (CF3)(2)CHOH and pyridine in CH2Cl2 gave the monocationic complexes [(L-a)Pd(CH3)(pyridine)](+)(A)(-) (A(-) = {B[(3,5-CF3)(2)C6H2)](4)}(-), (CF3)(2)CHO-); acetonitrile and benzonitrile analogues can be prepared in an analogous way. Reaction of 4a with AgBF4 in MeCN gave the dicationic complexes [(L-a)Pd(MeCN)(2)](BF4)(2). Complexes 3 show moderate catalytic activity for the coupling of acrylates with aryl bromides but not chlorides. The cationic species generated in situ from 3a and H(Et2O){B[(3,5-CF3)(2)C6H2)](4)} in CH2Cl2 under CO/ethylene acts as a copolymerization catalyst under mild conditions.