Synthesis and characterization of a monocyanide-bridged bimetallic iron(II) and copper(I) complex.
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The experiments reported here describe the interaction of the cyanide ligand in the neutral CpFe(CO)2CN derivative with copper(I) in both acetonitrile and methylene chloride solutions. In acetonitrile solution, acetonitrile competes with the Fe-CN moiety for binding to copper(I), where an equilibrium is established with Kcq = 4.3 x 103 ?? 25 C. On the other hand, in methylene chloride, complete adduct formation is observed. Adduct formation in solution is based on shifts of the vco and VCN vibrations to higher frequencies, as compared to the corresponding values in CpFe(CO)2CN, with vcN being more significantly affected by complex formation. Upon adding 2 equiv of PCy3 to a methylene chloride solution of CpFe(CO)2CN and Cu(CH3CN)4+, the complex cation CpFe(CO)2(-CN)Cu(PCy3)2+ is formed and isolated as its BF4- salt in crystalline form. X-ray crystallography has shown that the interatomic distances and angles in the parent complex CpFe(CO)2CN and its copper(I) adduct are quite similar. Further, the Fe-CN-Cu bridge is nonlinear, displaying a C-N-Cu angle of 161.3(5).