Tory Joanne, King Lisa, Maroulis Antonios, Haukka Matti, Calhorda Maria José, Hartl František
Department of Chemistry, University of Reading , Whiteknights, Reading, RG6 6AD, U.K.
Inorg Chem. 2014 Feb 3;53(3):1382-96. doi: 10.1021/ic402146t. Epub 2014 Jan 13.
Cyclic voltammetry and ultraviolet-visible/infrared (UV-vis/IR) spectroelectrochemistry were used to study the cathodic electrochemical behavior of the osmium complexes mer-[Os(III)(CO) (bpy)Cl3] (bpy = 2,2'-bipyridine) and trans(Cl)-[Os(II)(CO) (PrCN)(bpy)Cl2] at variable temperature in different solvents (tetrahydrofuran (THF), butyronitrile (PrCN), acetonitrile (MeCN)) and electrolytes (Bu4NPF6, Bu4NCl). The precursors can be reduced to mer-Os(II)(CO) (bpy(•-))Cl3 and trans(Cl)-Os(II)(CO)(PrCN) (bpy(•-))Cl2, respectively, which react rapidly at room temperature, losing the chloride ligands and forming Os(0) species. mer-[Os(III)(CO) (bpy)Cl3] is reduced in THF to give ultimately an Os-Os-bonded polymer, probably [Os(0)(CO) (THF)(bpy)]n, whereas in PrCN the well-soluble, probably mononuclear [Os(0)(CO) (PrCN)(bpy)], species is formed. The same products were observed for the 2 electron reduction of trans(Cl)-[Os(II)(CO)(PrCN) (bpy)Cl2] in both solvents. In MeCN, similar to THF, the [Os(0)(CO) (MeCN)(bpy)]n polymer is produced. It is noteworthy that the bpy ligand in mononuclear [Os(0)(CO) (PrCN)(bpy)] is reduced to the corresponding radical anion at a significantly less negative potential than it is in polymeric [Os(0)(CO) (THF)(bpy)]n: ΔE1/2 = 0.67 V. Major differences also exist in the IR spectra of the Os(0) species: the polymer shows a broad ν(CO) band at much smaller wavenumbers compared to the soluble Os(0) monomer that exhibits a characteristic ν(Pr-CN) band below 2200 cm(-1) in addition to the intense and narrow ν(CO) absorption band. For the first time, in this work the M(0)-bpy (M = Ru, Os) mono- and dicarbonyl species soluble in PrCN have been formulated as a mononuclear complex. Density functional theory (DFT) and time-dependent-DFT calculations confirm the Os(0) oxidation state and suggest that [Os(0)(CO) (PrCN)(bpy)] is a square planar moiety. The reversible bpy-based reduction of [Os(0)(CO) (PrCN)(bpy)] triggers catalytic reduction of CO2 to CO and HCOO(-).
采用循环伏安法和紫外可见/红外（UV-vis/IR）光谱电化学法，研究了锇配合物mer-[Os(III)(CO)(bpy)Cl3]（bpy = 2,2'-联吡啶）和反式(Cl)-[Os(II)(CO)(PrCN)(bpy)Cl2]在不同溶剂（四氢呋喃（THF）、丁腈（PrCN）、乙腈（MeCN））和电解质（Bu4NPF6、Bu4NCl）中，于不同温度下的阴极电化学行为。前体可分别还原为mer-Os(II)(CO)(bpy(•-))Cl3和反式(Cl)-Os(II)(CO)(PrCN)(bpy(•-))Cl2，它们在室温下迅速反应，失去氯配体并形成Os(0)物种。mer-[Os(III)(CO)(bpy)Cl3]在THF中被还原，最终生成一种Os-Os键合的聚合物，可能是[Os(0)(CO)(THF)(bpy)]n，而在PrCN中则形成了可溶的、可能为单核的[Os(0)(CO)(PrCN)(bpy)]物种。在两种溶剂中，反式(Cl)-[Os(II)(CO)(PrCN)(bpy)Cl2]经2电子还原也观察到了相同的产物。在MeCN中，与THF类似，生成了[Os(0)(CO)(MeCN)(bpy)]n聚合物。值得注意的是，单核[Os(0)(CO)(PrCN)(bpy)]中的bpy配体被还原为相应的自由基阴离子时，其负电位明显低于聚合物[Os(0)(CO)(THF)(bpy)]n中的：ΔE1/2 = 0.67 V。Os(0)物种的红外光谱也存在重大差异：聚合物显示出一个宽的ν(CO)带，其波数比可溶的Os(0)单体小得多，该单体除了有强烈且狭窄的ν(CO)吸收带外，在2200 cm(-1)以下还显示出特征性的ν(Pr-CN)带。在这项工作中，首次将可溶于PrCN的M(0)-bpy（M = Ru、Os）单羰基和二羰基物种配制成单核配合物。密度泛函理论（DFT）和含时DFT计算证实了Os(0)的氧化态，并表明[Os(0)(CO)(PrCN)(bpy)]是一个平面正方形部分。[Os(0)(CO)(PrCN)(bpy)]基于bpy的可逆还原引发了CO2催化还原为CO和HCOO(-)。
