FERROCENE-CONTAINING CHELATING LIGANDS .1. SOLUTION STUDY, SYNTHESIS, CRYSTAL-STRUCTURE, AND ELECTRONIC-PROPERTIES OF BIS(N,N'-ETHYLENEBIS((FERROCENYLMETHYL)AMINE))COPPER(II) NITRATE

The synthesis of the Schiff base N,N'-ethylenebis((ferrocenylmethylidene)amine), (eta5-C5H5)Fe[eta5-C5H4)CH=N-(CH2)2N=CH(eta5-C5H4)]Fe(175-C5H5) (1), its parent amine (eta5-C5H5)Fe[(eta5-C5H4)CH2NH(CH2)2NHCH2(eta5-C5H4)]Fe(eta5-C5H5),Fc2L (2), and the complex [Cu(Fc2L)2(NO3)2].2CH3OH (3) are reported. The protonation of 2 and its complex formation with copper(II) have been investigated by potentiometry in dimethyl sulfoxide (dmso)-water (80:20 w/w) mixtures at 25-degrees-C and 0.1 mol dm-3 KClO4. The molecular structure of 3 has been determined by single-crystal X-ray analysis. It crystallizes in the triclinic system, space group P1BAR, a = 7.520(1) angstrom, b = 11.047(2) angstrom, c = 16.186(5) angstrom, alpha = 101.93(2)-degrees, beta = 97.24(2)-degrees, gamma = 104.95(1)-degrees, Z = 1, and V = 1247.9(5) angstrom3. Refinement of the atomic parameters by least-squares techniques gave a final R factor of 0.046 (R(w) = 0.051) for 2941 unique reflections having I > 2.5sigma(I). The structure of 3 consists in discrete [Cu(FC2L)2(NO3)2] neutral units in which the copper(II) ion exhibits a distorted octahedral environment: the four equatorial positions are occupied by the nitrogen atoms of the bidentate ligand, Fc2L, whereas the apical sites are filled by oxygen atoms of weakly coordinated nitrate anions. 3 is actually a pentanuclear complex with four ferrocene groups which oxidize at the same potential as shown by cyclic voltammetry. So, this compound is a four-electron reservoir potentially capable of acting as a multielectron mediator in redox catalytic reactions. Its electronic properties have been characterized by spectroscopic techniques and variable-temperature magnetic susceptibility measurements.