Light-Induced Decarbonylation, Solvolysis, and Isomerization of Ru(L)(CO)₂Cl₂ (L = 2,2‘-Bipyridine and 4,4‘-Dimethyl-2,2‘-bipyridine) in Acetonitrile

Abstract

The photochemical properties of Ru(II) mono(bipyridine) complexes Ru(L)(CO) 2 Cl 2 [L ) 2,2′-bipyridine (1, 2) or 4,4′-dimethyl-2,2′-bipyridine (3)] were studied in CH 3 CN and CH 2 Cl 2 . Photochemical ligand substitution reactions occurring in CH 3 CN were followed by infrared and 1 H NMR spectroscopies and cyclic voltammetry. The structures of the photolysis products Ru(bpy)(CO)(CH 3 CN)Cl 2 (4), mer-(CH 3 CN) Ru(bpy)(CH 3 CN) 3 Cl + (6), and fac-(CH 3 CN) Ru(dmbpy)(CH 3 CN) 3 Cl + (8) were determined by single-crystal X-ray crystallography. Photosubstitution of the trans (1) and cis (2) Cl isomers of Ru(bpy)(CO) 2 Cl 2 (bpy ) 2,2′-bipyridine) led to the same monosubstituted Ru(bpy)(CO)(CH 3 CN)Cl 2 complex (4). Probably some isomerization occurs from the trans Cl isomer. Irradiation in CH 2 Cl 2 led mainly to the dichloro-bridged [Ru(bpy)(CO)Cl 2 ] 2 (5) dimer starting from either the trans (1) or cis (2) isomer of Ru(bpy)(CO) 2 Cl 2 .

Novel Complexes trans(Cl)-[Os(bpy)(CO)(CH3CN)Cl2]n (n = 0, +1; bpy = 2,2′-Bipyridine): Photo- and Electrochemical Syntheses and Comparative Study of Their Bonding and Redox Properties

“…2 Cl 2 ] (Me-DAB ϭ N,NЈ-dimethyl-1,4-diaza-1,3-butadiene) have revealed a mixed XLCT/MLCT character of its lowest-energy allowed electronic transition, while CASSCF/CASPT2 ab initio calculations favour its predominant MLCT assignment. [ is formed from trans(Cl)-[Ru(bpy)(CO) 2 Cl 2 ] markedly more rapidly (within a few minutes), [7,9] again consistent with weaker RuϪCO bonds in the reactive excited state and in analogy with the electrochemical oxidation. It is also possible that for the less photoreactive 5d-Os complex 1 a branching of the FranckCondon excited state evolution occurs, resulting in a competition between CO-loss reactivity from the dissociative state and parallel population of an unreactive excited state.…”

“…Schematic molecular structure of complex 2 with numbering of 2,2Ј-bipyridine proton nuclei for assignment of 1 [ν(CO) at 1969 cm Ϫ1 ; CH 3 CN]. [9] The typically smaller ν(CO) wavenumbers for the osmium() compounds compared to their ruthenium() derivatives [∆ν(CO) ഠ 30 cm Ϫ1 for corresponding bands] reflect the stronger bond between CO and the 5d metal atom.…”

Towards New Molecular Photocatalysts for CO2 Reduction: Photo‐Induced Electron Transfer versus CO Dissociation within [Os(NN)(CO)2Cl2] Complexes

“…Under irradiation the excited states of the complexes relax on the picosecond time scale only through the ligand-field (or metalcentred) dissociative state, which induces a fast and efficient CO-release reaction preventing photoredox processes. [15] The equivalent osmium complexes have undergone much less exhaustive studies. In a general way osmium complexes are more stable, because the third-row metal atoms form stronger coordination bonds than those of the first-and second-row metals and present more attractive reactivity upon optical excitation.…”

A Novel Organometallic Polymer of Osmium(0), [Os(2,2′-bipyridine)(CO)2]n: Its Electrosynthesis and Electrocatalytic Properties Towards CO2 Reduction

“…[5] It also exhibits interesting photochemical properties. [6] We could reasonably expect formation of an analogous Os 0 organometallic polymer by the electrochemical reduction of the parent mononuclear osmium(II) complex trans(Cl)-[Os(bpy)(CO) 2 Cl 2 ] (1), which has recently been synthesized but only superficially characterized. [7] We present here a preliminary electrochemical study of 1 which confirms that films of the [Os(bpy)(CO) 2 ] n polymer can indeed be prepared effectively.…”