Crystal and molecular structure of [α-N-(o-hydroxybenzyl)-L-histidinato](L-alaninato) cobalt(III) dihydrate

The crystal and molecular structure of [α-N-(o-hydroxybenzyl)-L-histidinato](L-alaninato)cobalt(III) dihydrate has been determined by three-dimensional x-ray analysis. The compound crystallizes in the orthorhombic space group P212121, with a = 13.188 (2) A, b = 18.140 (2) A, c = 7.842 (1) A, and Z = 4. The structure was solved by the heavy-atom method and refined by full-matrix least-squares procedures to a final discrepancy factor R = 0.059 for 3553 observed reflections (I/sub obsd/ > or = 3 sigma/sub I/). The geometry around the cobalt ion is distorted octahedral. The α-N-(o-hydroxybenzyl)-L-histidinato ligand is tetradentate, bonding through the imidazole nitrogen, carboxylate oxygen, secondary amino nitrogen, and phenolate oxygen atoms. The histidinate fragment of the tetradentate ligand occupies one face of the coordination octahedron with the phenolate oxygen of the o-hydroxybenzyl substituent occupying the position trans to the histidinate carboxyl oxygen. The bidentate L-alaninate ligand is attached with its amino nitrogen trans to the imidazole nitrogen and its carboxylate oxygen trans to the secondary amino nitrogen of the tetradentate ligand. The L-alaninato five-membered chelate ring adopts the conformation of an asymmetric envelope