181185-75-1Relevant academic research and scientific papers
Synthesis and reactivity of aryl- and alkyl-palladium(II) complexes with functional phosphines and phosphinoenolate ligands: First analogues of model nickel catalysts
Andrieu, Jacques,Braunstein, Pierre,Naud, Frederic
, p. 2903 - 2909 (2007/10/03)
Phenyl- and methyl-palladium(II) complexes analogous to model nickel(II) catalysts were prepared from readily available precursors. The methods used allow different ligands to be introduced in the co-ordination sphere. For example, the chelating phosphinoenolate ligand in [PdPh{Ph2PCH-..C(-..O)NPh2}L 2] [L2 = Ph2PCH2C(O)NPh2] was displaced by 1 equivalent of Ph2PCH2C(O)Ph(L1) to give [PdPh{Ph2PCH-..C(-..O)Ph}L2] whereas the terminal functional phosphine was displaced by P(C6H11)3 to give [PdPh{Ph2PCH-..C(-..O)NPh2}{P(C 6H11)3}]. Owing to favourable ligand-redistribution reactions, treatment of a mixture of complexes trans-[PdMe(Cl)L22], trans-[PdMe(Cl)L12] and trans-[PdMe(Cl)L1(L2)] (which cannot be isolated pure) with an excess of NaOMe in toluene selectively afforded the phosphinoenolate complex [PdMe{Ph2PCH-..C(-..)Ph}L2]. The enolate moiety of [PdPh{Ph2PCH-..C(-..O)NPh2}L 2] and of [PdMe{Ph2PCH-..C(-..O)NPh2}L 2] reacted with R′N=C=O (R′ = Ph or p-tolyl) with formation of a carbon-carbon bond in a Michael-type addition and the products were shown to exist in the form of two isomers a and b, characterised by a N-H ... O or a N-H ... N hydrogen bond within the ligand system. Insertion of CO into the Pd-Me bond of [PdMe{Ph2PCH-..C(-..O)NPh2}L 2] or [PdMe{Ph2C[=C(O)NHPh]C(O)NPh2}L2] yielded the corresponding acyl complexes. Although [PdMe{Ph2PCH-..C(-..O)Ph}(PPh3)] inserted ethylene into its Pd-Me bond, as evidenced by quantitative formation of propylene, the palladium hydride that must be generated by the β-elimination reaction decomposes before further ethylene insertion can occur.
