STRUCTURAL, MAGNETIC AND SPECTROSCOPIC CHARACTERIZATION OF NOVEL DI-MU-CARBOXYLATO-BRIDGED BINUCLEAR COPPER(II) COMPLEXES WITH 1,10-PHENANTHROLINE

Bis(μ-carboxylato-O,O')-diaquabis(1,10-phenanthroline)dicopper(II) dinitrate tetrahydrates, [Cu(RCOO)(phen)(H2O)]2(NO3)24H2O, where R=H, CH3, and (CH3)3C, were prepared and characterized by elemental analyses, electronic spectra, magnetic susceptibilities, and X-ray structure analysis. The magnetic susceptibility data conform to the usual dimer equation. The -2J values are 125 cm-1 for formate, 86 cm-1 for acetate, and 99 cm-1 for 2.2-dimethylpropanoate. The crystal structures of [Cu(HCOO)(phen)(H2O)]2(NO3)24H2O(1) and [Cu(CH3COO)(phen)(H2O)]2(NO3)24H2O (2) were determined by the single-crystal X-ray diffraction method. The crystallographic data are: Compound 1, monoclinic, 12/a, a=18.850(2), b=9.775(2), c=17.752(2) A, β=99.03(1)°, V=3230.4(8) A3, Z=4, R=0.055 for 2511 observed unique reflections; Compound 2, monoclinic, C2/c, a=18.563(4), b=14.272(5), c=14.126(3) A, β=106.72(2)°, V=3584(2) A3, Z=4, R=0.082 for 2092 reflections. The complexes consist of dimeric [Cu(RCOO)(phen)(H2O)]2 +2 cations with five-coordinated copper ions linked by two carboxylato ions in a syn-syn bridging arrangement. The Cu...Cu distances are 3.103(2) A for 1 and 3.063(3) A for 2.