Yu Rongmin, Arumugam Kuppuswamy, Manepalli Ashok, Tran Yvon, Schmehl Russell, Jacobsen Heiko, Donahue James P
Department of Chemistry, Tulane University, 6400 Freret Street, New Orleans, Louisiana 70118-5698, USA.
Inorg Chem. 2007 Jun 25;46(13):5131-3. doi: 10.1021/ic0624569. Epub 2007 May 19.
The homoleptic bis(dithiolene) complexes M(S(2)C(2)R(2))(2) (M = Fe, Co; R = p-anisyl) undergo two successive reductions to form anions that display M(S(2)C(2)R(2))(2)(2-) <--> 2M(S(2)C(2)R(2))(2) solution equilibria. The neutral dimers react with Ph3P to form square pyramidal M(Ph(3)P)(S(2)C(2)R(2))(2). Voltammetric measurements upon M(Ph(3)P)(S(2)C(2)R(2))(2) in CH(2)Cl(2) reveal only irreversible features at negative potentials, consistent with Ph(3)P dissociation upon reduction. Dissociation and reassociation of Ph(3)P from and to Fe(Ph(3)P)(S(2)C(2)R(2))(2) is demonstrated by spectroelectrochemical measurements. These collective observations form the basis for a cycle of reversible, electrochemically controlled binding of Ph(3)P to M(S(2)C(2)R(2))(2) (M = Fe, Co; R = p-anisyl). All members of the cycle (M(S(2)C(2)R(2))(2)(0), M(S(2)C(2)R(2))(2)(1-), MM(S(2)C(2)R(2))(2)(2-), M(S(2)C(2)R(2))(2), [M(Ph(3)P)(S(2)C(2)R(2))(2)]) for M = Fe, Co have been characterized by crystallography. Square planar Fe(S(2)C(2)R(2))(2) is the first such iron dithiolene species to be structurally identified and reveals Fe-S bond distances of 2.172(1) and 2.179(1) Angstrom, which are appreciably shorter than those in corresponding square planar dianions.
同配双（二硫纶）配合物[M(S₂C₂R₂)₂]²（M = Fe，Co；R = 对甲氧基苯基）经历两步连续还原形成阴离子，这些阴离子在溶液中存在[M(S₂C₂R₂)₂]²²⁻⇌2[M(S₂C₂R₂)₂]¹⁻的平衡。中性二聚体与三苯基膦反应生成正方锥型的[M(Ph₃P)(S₂C₂R₂)₂]⁰。在二氯甲烷中对[M(Ph₃P)(S₂C₂R₂)₂]⁰进行伏安测量，结果显示在负电位下只有不可逆特征，这与还原时三苯基膦的解离一致。通过光谱电化学测量证明了三苯基膦在[Fe(Ph₃P)(S₂C₂R₂)₂]⁰上的解离和重新结合。这些总体观察结果构成了三苯基膦与[M(S₂C₂R₂)₂]²（M = Fe，Co；R = 对甲氧基苯基）进行可逆的、电化学控制结合循环的基础。该循环的所有成员（[M(S₂C₂R₂)₂]²⁰、[M(S₂C₂R₂)₂]²¹⁻、[M(S₂C₂R₂)₂]²²⁻、[M(S₂C₂R₂)₂]¹⁻、[M(Ph₃P)(S₂C₂R₂)₂]）对于M = Fe、Co均已通过晶体学进行了表征。平面正方形的[Fe(S₂C₂R₂)₂]¹⁻是首个在结构上被鉴定的此类铁二硫纶物种，其Fe - S键长为2.172(1)和2.179(1)埃，明显短于相应平面正方形二价阴离子中的键长。
