The crystal and molecular structure of di-μ-hydroxobis[di(1,10-phenanthroline)chromium(III)] chloride hexahydrate

The crystal and molecular structure of di-μ-hydroxobis[di(1,10-phenanthroline)chromium(III)] chloride hexahydrate, [Cr(phen)₂OH]₂Cl₄.6H₂O, has been determined from three-dimensional counter X-ray data. The material crystallizes in the triclinic space group P1 with two dimeric formula units in a cell whose dimensions are a = 14.056 (7), b = 11.296 (6), c = 18.990 (9) Å, α = 87.15 (3), β = 107.63 (2) and γ = 74.68 (3)°. The observed and calculated densities are 1.39 (4) and 1.342 g cm⁻³, respectively. The structure has been refined by full-matrix least-squares techniques to a conventional R value of 0.077 for 3392 independent intensities greater than three times their estimated standard deviations. The complex consists of pairs of chromium atoms which are linked by two hydroxo bridges, with two 1,10-phenanthroline groups coordinated to each metal; the coordination geometry around each chromium is roughly octahedral. The average Cr—N and Cr—O bond lengths are 2.052 (6) and 1.927 (6) Å, respectively, while the Cr—Cr separation is 3.008 (3) Å and the average Cr—O—Cr angle is 102.7 (4)°. The geometry of this complex is compared with that of [Cr(gly)₂OH]₂ and with those of complexes of the type [CuLOH]ⁿ⁺₂, and the magnetic properties of the complex are discussed in terms of the bridging geometry.