Lunsford Allen M, Goldstein Kristina F, Cohan Matthew A, Denny Jason A, Bhuvanesh Nattamai, Ding Shengda, Hall Michael B, Darensbourg Marcetta Y
Department of Chemistry, Texas A&M University, College Station, Texas, USA.
Dalton Trans. 2017 Apr 19;46(16):5175-5182. doi: 10.1039/c7dt00600d.
The bipyridine ligand is renowned as a photo- and redox-active ligand in catalysis; the latter has been particularly explored in the complex Re(bipy)(CO)Cl for CO reduction. We ask whether a bidentate, redox-active MNS metallodithiolate ligand in heterobimetallic complexes of Mn and Re might similarly serve as a receptor and conduit of electrons. In order to assess the electrochemical features of such designed bimetallics, a series of complexes featuring redox active MNS metallodithiolates, with M = Ni, {Fe(NO)}, and {Co(NO)}, bound to M'(CO)X, where M' = Mn and Re, were synthesized and characterized using IR and EPR spectroscopies, X-ray diffraction, cyclic voltammetry, and density functional theory (DFT) computations. Butterfly type structures resulted from binding of the convergent lone pairs of the cis-sulfur atoms to the M'(CO)X unit. Bond distances and angles are similar across the M' metal series regardless of the ligand attached. Electrochemical characterizations of [MNS·Re(CO)Cl] showed the redox potential of the Re is significantly altered by the identity of the metal in the NS pocket. DFT calculations proved useful to identify the roles played by the MNS ligands, upon reduction of the bimetallics, in altering the lability of the Re-Cl bond and the ensuing effect on the reduction of Re to Re.
联吡啶配体在催化领域作为光活性和氧化还原活性配体而闻名;后者在配合物Re(bipy)(CO)Cl中用于CO还原方面得到了特别研究。我们探究在Mn和Re的异双金属配合物中,一种双齿、氧化还原活性的MNS金属二硫醇盐配体是否同样可以作为电子受体和传导体。为了评估此类设计的双金属化合物的电化学特性,合成了一系列具有氧化还原活性MNS金属二硫醇盐的配合物,其中M = Ni、{Fe(NO)}和{Co(NO)},它们与M'(CO)X相连,这里M' = Mn和Re,并使用红外光谱和电子顺磁共振光谱、X射线衍射、循环伏安法以及密度泛函理论(DFT)计算对其进行了表征。蝴蝶型结构是由顺式硫原子的收敛孤对与M'(CO)X单元结合产生的。无论连接何种配体,整个M'金属系列的键长和键角都相似。[MNS·Re(CO)Cl]的电化学表征表明,NS口袋中金属的特性会显著改变Re的氧化还原电位。DFT计算有助于确定双金属化合物还原时MNS配体在改变Re-Cl键的活性以及对Re还原为Re的后续影响中所起的作用。