Hydrogen bonding in cis-bis(L-alaninato)copper(II): a single crystal neutron diffraction study

The structure of cis-bis(L-alaninato)copper(II) {cis-[Cu(L-ala)(2)]} was de termined using single crystal neutron diffraction techniques at both low (7 K) and ambient temperature. At both temperatures the cell is orthorhombic, space group P2(1)2(1)2(1). The unit cell parameters obtained show essentia lly an isotropic contraction upon cooling. At both temperatures the coordin ation sphere around the copper atom is best described as square pyramidal, where the fifth position is occupied by a weakly bonded carbonyl oxygen fro m an adjacent alanine unit. The alanine ligands coordinate to the divalent copper atom in an approximately square planar cis-arrangement. The signific ant difference between the two structure determinations is the contraction of the apical carbonyl oxygen-copper bond distance from 2.372(4) to 2.326(2 ) Angstrom upon cooling. (C) 1999 Elsevier Science S.A. All rights reserved .