The electronic structure of Ru(III)-ammine complexes and the product distribution from solid-state thermal reaction

INDO-type UHF-MO calculations were carried out for Ru(III)-ammine complexes in order to investigate their electronic structures and bonding nature. It was revealed that the ground state of RuX(NH3)52+(X=F, Cl, Br, or I) is the 2E state and that of cis-RuX2(NH3)4+ is the 2A1 state; in RuX(NH3)52+, the odd electron exists not on the d sub(xy) orbital but on the d sub(xz) or d sub(yz) orbital which interacts with the p sub(π)-orbital of the halide ligand, and in cis-RuX2(NH3)4+, this electron exists not on the d sub(xz) or d sub(xy) orbital but on the d sub(yz) orbital which interacts with the p sub(π) orbitals of the two halide ligands. Concerning the bonding nature, the following results were obtained: (1) the strength of the Ru-NH3 bond in these complexes increases in the order, cis-RuX2(NH3)4+<RuX(NH3)52+<Ru(OH2)(NH3)53+<Ru(NH3)63+; (2) in the aqua-ammine complex, the Ru-OH2 bond is weaker than the Ru-NH3 bond; and (3) in the halogeno-ammine complexes, the trans-Ru-NH3 bond is weaker than the cis-Ru-NH3 bond. MO calculations were also carried out for some distorted states of RuCl(NH3)52+. From these results, a discussion is presented on the relation between the thermal reaction product and the reaction mechanism; cis-RuCl2(NH3)4+ is expected to be produced via an associative reaction mechanism, while the trans-form product is expected to result from a dissociative mechanism. (auth.)