Studies of Complexes of Potential Catalytic Uses

Abstract

The importance of studying transition metal organonitrile complexes in order to determine how to achieve the activation of a nitrile is discussed. Two transition metal complex systems were selected based on their proven ability to react with dinitrogen and on the grounds of their potential use in the generation of industrially useful homogeneous catalysts. [Ru (R'NH2)5 (PhCN)] 2+ and CoH(X)(PR3)3, where R' = CH3-, C2H5-, C3H7- and C4H9- ; X = N2, CH3CN and PhCN; R = n-octyl-, n-butyl- and phenyl-. The preparations and characterisation of some new hexakisamine and benzonitrilepentakisamine complexes of ruthenium(II) are reported together with the assignment of the ruthenium nitrogen stretching mode. Also the change in the carbon nitrogen triple bond stretching frequency for the coordinated benzonitrile ligand with the increasing σ donor ability of the amine and with change of counter anion is discussed. The unusual oxidative degradation of the hexakis--methylamineruthenium(II) complex is reported and the products are shown to be a ruthenium cyanide Ru(CN)3, a methylammoniun salt and water. Oxidation of the long chained amine complexes is less simple, since the reaction yields a black tarry intractable material, the infra-red spectrum of which shows the presence of small traces of organonitrile, identified by its characteristic carbon nitrogen triple bond stretching frequency. The kinetics of the reaction between oxygen and the hexakismethylamineruthenium(I1) complex dissolved in water at various ionic concentrations and temperatures is discussed. By following the appearance of a band at 318nm and the rate of oxygen uptake a mechanism for the overall reaction is proposed. Syntheses and characterisation of the cobalt trialkylphosphine complexes with dinitrogen or organonitriles are outlined together with their subsequent reaction with excess triethyl aluminium. This reaction was followed by infra-red and electron spin resonance spectroscopy leading to the assignment of the carbon nitrogen triple bond stretching bands at frequencies lower than any previously observed for mononitrile metal complexes.