A bis-acetonitrile two-coordinate copper(I) complex:: Synthesis and characterization of highly soluble B(C6F5)4- salts of [Cu(MeCN)2]+ and [Cu(MeCN)4]+

Copper(I)-acetonitrile complexes are exceedingly useful starting materials for the synthesis of copper(I) complexes with polydentate ligands. To extend the utility of such chemistry to solution studies in relatively low-dielectric solvents (i.e., diethyl ether, toluene) and to aid in obtaining products amenable to X-ray diffraction studies, we have recently begun to employ counteranions such as B(C6F5)(4)(-) for bioinorganic studies. Thus, the synthesis of [Cu(MeCN)(4)]B(C6F5)(4) (1) is presented. Its recrystallization from CH2Cl2/pentane yields the linear, two-coordinate complex [Cu(MeCN)(2)]B(C6F5)(4) (2), whose centrosymmetric X-ray structure shows that its Cu-N distance is significantly shorter than that in other two-coordinate Cu(I) complexes with nitrogen ligands or that in the tetrahedral complex [Cu(MeCN)(4)]CIO4. Infrared spectroscopy indicates interesting and diagnostically useful differences between the v(CN) of 1 and 2.