Dialkylargentate (I) decompositions and the heterogenization of analogous complexes for catalyst preparations

Abstract

Lithium di-n-butyl(tri-n-butylphosphine)argentate(I) (2) and other organoargentate(I) complexes have been prepared and their mechanism of thermal decomposition studied. Chemical characterization of 2 by reaction first with dibromoethane and then iodine yielded only l-iodobutane, showing that 2 was formed quantitatively. ('13)C and ('31)P NMR spectra of lithium dimethyl(tri-n-butylphosphine)argentate(I) are described which support this conclusion. Dilithium trimethyl(tri-n-butylphosphine)argentate(I) was also identified by ('13)C NMR. Analysis of the products of thermal decomposition of 2 suggests that the observed thermal stabilization of 2 with respect to the rapid thermal decomposition of n-butyl(tri-n-butylphosphine)silver(I) (1) is the result of an altered mechanism for carbon-silver bond cleavage. Lithium di-n-butyl(tri-n-butylphosphine)argentate(I) is proposed to decompose to give products derived from n-butyl radicals and n-butyllithium. The principle thermal decomposition products from 2 were octane (26%), butane (71%) and 1-butane (3%). Crossover experiments in which mixed lithium n-butyl(n-pentyl)argentate(I) was thermally decomposed yielded a statistical distribution of coupled products. Substitution of magnesium bromide for lithium had no effect on the product mixture from these thermal decomposition reactions. Kinetics of decomposition of 2 were first order in 2. Other possible pathways for decomposition of organoargentate(I) complexes are discussed and the suggested mechanism for this thermal decomposition reaction is compared to similar organocopper(I) and organogold(I) chemistry. ...