Structural and Spectroscopic Properties of Two New Isostructural Complexes of Lapacholate with Cobalt and Copper

Abstract

The molecular structures of two isostructural complexes of lapacholate (Lap) anion and dimethylformamide (DMF), M(Lap)2(DMF)2 with M: Co Cu, were determined by X-ray diffraction methods. The substances crystallize in the triclinic space group P1 with one molecule per unit cell and cell constants a = 7.7591(3), b = 10.3560(3), c = 11.2224(4) A, ˚ α = 95.110(2), β = 94.310(2), and γ = 107.704(2)◦ for the Co complex and a = 7.9308(2), b = 10.0033(4), c = 10.7508(4), α = 97.387(2), β = 93.621(2), and γ = 103.980(2)◦ for the Cu complex. The structures were solved from 2933 (Co) and 2888 (Cu) reflections with I > 2σ (I) and refined by full matrix least squares to agreement R1-factors of 0.041 (Co) and 0.033 (Cu). The metal M(II) ion is sited on a crystallographic inversion center in a MO6 distorted octahedral environment. This ion is coordinated equatorially to two lapacholate anions through their adjacent carbonyl and phenol oxygen atoms [M–O bond distances of 2.134(1) and 2.008(1) A˚ (Co) and 2.301(1) and 1.914(1) A (Cu)] and axially to two DMF molecules through oxygen atoms [M–O bond lengths of 2.143(1) ˚ A (Co) and 2.069(1) ˚ A (Cu)]. The solid state IR transmittance and solution electronic absorption spectra of both Co and Cu ˚ compounds are also reported and compared to each other and to the corresponding spectra of other members of the lapacholate metal family of complexes.