Electrophilic nitrosyls: preparation, structure, and reactivity of cis-chloronitrosylbis(pyridine-2-carboxylato)ruthenium and related complexes

Abstract

Reaction of [RuCl₅(NO)]^2– with pyridine-2-carboxylic acid (Hpyca) at pH 4.5 gave cis[RuCl(pyca)₂(NO)], isomer(I), with the acetate groups co-ordinated trans to the nitrosyl and chloro-ligands and the pyridine nitrogens trans to one another, as proved by an X-ray crystallographic investigation. Crystal data: orthorhombic, space group P2₁2₁2₁, a=15.297(8), b=11.401(5), and c= 8.224(3)Å; R= 0.072. A second product of the reaction was [RuCl₃(pyca)(NO)]^–. At pH 7 the reaction gave a second isomer of cis-[RuCl(pyca)₂(NO)], (II), with the acetate oxygen trans to NO and a pyridine nitrogen traps to Cl. Reaction of quinoline-2-carboxylic acid (Hgnca) with [RuCl₅(NO)]^2–at pH 4.5 gave cis-[RuCl(qnca)₂(NO)], isomer (II), and at pH 7 [Ru(OH)(qnca)₂(NO)]. With [OsCl₅(NO)]^2– and Hpyca only [OsCl₃(pyca)(NO)]^–, was obtained. It was not possible to isomerise isomer (I) thermally without decomposition by loss of HCl. Reactions of the nitrosyl group in isomers (I) and (II) with nucleophiles were complicated by ligand-replacement reactions.