Tripodal Oxygen Ligand Supported Palladium(II) Complexes: Alkylation, Carboxymethylation, and CO Insertion Reactions - X-ray Crystal Structure Determination of [PdL_2], L~- = [(C_5H_5)Co{P(O)(OMe)_2}_3]~-, a Novel Homoleptic Oxygen Ligand Palladium C

摘要

The reaction of [PdCl_2(CH_3CN)_2] with the silver salt of the tripodal oxygen ligand L~- = [(C_5H_5)Co{P(O)(OMe)_2)}_3]~- yields the homoleptic oxygen ligand complex [PdL_2] (1). The molecular structure of 1 was determined by single-crystal X-ray diffraction: monoclinic space group P2_1; a = 8.515(1), b = 13.627(2), c = 15.828[2) A; β = 92.44(1)°; V = 1834.9(7) A~3; Z = 2. The complexes [Pd(PPh_3)XL] [X = Cl (2a), Br (2b), I (2c)] have been prepared starting from 1. Complex 2a reacts with PPh_3 to form [Pd(PPh_3)_2L]Cl (3a) and [Pd(PPh_3)_2L]L (3b). Treatment of 2a with CO in MeOH yields the carboxymethyl complex [{PPh_3)(COOMe)Pd(μ-Cl)}_2] (4) and the protonated ligand HL. The carboxymethyl complex 4 shows some catalytic activity for the copolymerization of CO and ethene. Complex 4 reacts with AgL to yield [Pd(PPh_3)(COOMe)L] (6). Alkylation of 2a with Me_4Sn leads to the methyl complexes [Pd(PPh_3)MeL] (7) and [Me_2ClSnL] (8). CO insertion in the palladium-carbon bond of 7 gives the stable acetyl complex [Pd(PPh_3){C(O)Me}L] (10). The palladium(II) complexes 1, 2, 3, 6, 7, and 10 of the tripodal oxygen ligand L are all fluxional molecules that have been studied by temperature-dependent ~1H- and ~(31)P-NMR spectroscopy.