Palladium superoxido complexes. In what way (σ or π) is O₂^–co-ordinated? A quantum chemical approach

Abstract

The relative stability of palladium superoxido complexes, formed via o-or n-type co-ordination of a superoxide ion in monomeric and trimeric palladium species, has been investigated by CNDO-S2, a semi-empirical quantum chemical SCF-m.0. method. The CN DO-S2 method has been adapted to calculate the energetic and geometric properties of transition-metal compounds. A n-type co-ordination for 0,is calculated t o be most stable for monomeric palladium species, while o-type co-ordination is favoured for trimeric species. Experimental data on the reactivity of palladium superoxido complexes towards the epoxidation of simple alkenes are in agreement with the results of CNDO-S2 calculations.

Kinetics and mechanism of hydrogen peroxide decomposition in the presence of the tetraaquapalladium(II) complex

“…Second, being a strong electron acceptor, a C(NO 2 ) 4 molecule reacts efficiently with the low valence metal species (in this case, Pd I ). However, the influence of tetranitromethane on the kinetics of re action (1) can be considered as a fact confirming that reaction (14) is a rate determining step, because the oxi dation of any above mentioned species with tetranitro methane prevents reactions (16)- (19) or (21), (22), due to which the consumption rate of hydrogen peroxide de creases twofold.…”