Tripodal oxygen ligand supported palladium(II) complexes: Alkylation, carboxymethylation, and CO insertion reactions - X-ray crystal structure determination of [PdL2], L- = [(C5H5)Co{P(O)(OMe)(2)}(3)](-), a novel homoleptic oxygen ligand palladium complex

The reaction of [PdCl2(CH3CN)(2)] with the silver salt of the tripodal oxyg en ligand L- = [(C5H5)Co{P(O)(OMe)(2))}(3)](-) yields the homoleptic oxygen Ligand complex [PdL2] (1). The molecular structure of 1 was determined by single-crystal Xray diffraction: monoclinic spade group P2(1)/n; a = 8.515( 1), b = 13.627(2), c = 15.828(2) Angstrom; beta = 92.44(1)degrees; V = 1834 .9(7) Angstrom(3); Z = 2. The complexes [Pd(PPh3)XL] [X = Cl (2a), Br (2b), I (2c)] have been prepared starting from 1. Complex 2a reacts with PPh3 to form [Pd(PPh3)(2)L]Cl (3a) and [Pd(PPh3)(2)L]L (3b). Treatment of 2a with CO in MeOH yields the carboxymethyl complex [{(PPh3)(COOMe)Pd(mu-Cl)}(2)] ( 4) and the protonated ligand HL. The carboxymethyl complex 4 shows some cat alytic activity for the copolymerization of CO and ethene. Complex 4 reacts with AgL to yield [Pd(PPh3)(COOMe)L] (6). Alkylation of 2a with Me4Sn lead s to the methyl complexes [Pd(PPh3)MeL] (7) and [Me2ClSnL] (8). CO insertio n 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 studie d by temperature-dependent H-1- and P-31-NMR spectroscopy.