Département de chimie moléculaire

A novel synthesis method is introduced for the prepn. of [Os(NN)(CO)2X2] complexes (X = Cl, Br, I, and NN = 2,2'-bipyridine (bpy) or 4,4'-dimethyl-2,2'-bipyridine (dmbpy)). In the first step of this two-step synthesis, OsCl3 is reduced in the presence of a sacrificial metal surface in an alc. soln. The redn. reaction produces a mixt. of trinuclear mixed metal complexes which after the addn. of bpy or dmbpy produce a trans(Cl)-[Os(NN)(CO)2Cl2] complex in 60-70{%} yield. The halide exchange of [Os(bpy)(CO)2Cl2] has been performed in a concd. halidic acid (HI or HBr) soln. in an autoclave producing 30-50{%} of the corresponding complex. All of the synthesized trans(X)-[Os(bpy)(CO)2X2] (X = Cl, Br, I) complexes displayed a similar basic electrochem. behavior to that found in the ruthenium analog trans(Cl)-[Ru(bpy)(CO)2Cl2] studied previously, including the formation of an electroactive polymer [Os(bpy)(CO)2]n during the two-electron electrochem. redn. The absorption and emission properties of the osmium complexes were also studied. Compared to the ruthenium analogs, these osmium complexes display pronounced photoluminescence properties. The DFT calcns. were made in order to det. the HOMO-LUMO gaps and to analyze the contribution of the individual osmium d-orbitals and halogen p-orbitals to the frontier orbitals of the mols. The electrochem. and photochem. induced substitution reactions of carbonyl with the solvent mol. are also discussed. [on SciFinder(R)]