Syntheses and coordination chemistry of methylpyridylphosphine oxide ligands with copper(II)

The coordination properties of three heterofunctional phosphine oxide ligands, 2-methylpyridyldiphenylphosphine oxide (L1), phenylphosphino-bis-2-methylpyridine oxide (L2) and phenylphosphino-bis-2-methylpyridine N,N′,P-trioxide (L3) with Cu(II) is described. The X-ray crystal structures of the compounds display a distorted octahedral geometry, which exhibit Jahn–Teller distortions. In compounds 1 and 2, the L1 and L2 ligands react with Cu(BF4)2 in a 2:1 ligand to metal ratio, respectively, with the BF4 anions interacting with the metal center. L3 reacts with Cu(BF4)2 in 1:1 and 2:1 ligand/metal ratios to form compounds 3 and 4, respectively. Addition of either 2,2′-bipyridine or 4,4′-bipyridine to reaction solutions containing Cu(BF4)2 and L3 produces a discrete molecule (5) and a polymeric structure (7), respectively. The reaction of both bipyridines in the presence of Cu(BF4)2 and L3 gives rise to a discrete molecule (6) characterized by two octahedral coppers interconnected by the 4,4′-bipyridine. The electrochemical and photophysical properties of all compounds were investigated by cyclic voltammetry (CV) and UV–Vis, as they exhibited no emission or excitation in fluorimetric experiments.

Oxidation of 2-methylpyridylphosphines of the type PPhxCH2py3−x (x = 1, 2) afforded two novel phosphine oxide ligands whose coordination properties towards Cu(BF4)2·xH2O were investigated obtaining a series of discrete molecules and one polymeric structure when 4,4′-bipyridine was used to link the metal centers.Figure optionsDownload as PowerPoint slide