The crystal and molecular structure of the electron transfer complex butane-2, 3-dione-bis(2′-pyridyl-hydrazonato)nickel, [Ni(BDPH)-2H

Abstract

The neutral complex butane-2,3-dione-bis(′pyridylhydrazonato)nickel, [Ni(BDPH)-2H], obtained by deprotonation of butane-2,3-dione-bis(2′-pyridylhydrazono)nickel(II) cation, Ni(BDPH) 2+, crystallizes in the monoclinic P2 1/c space group with four molecule in a unit cell of dimensions a = 16.278(20) Å, b = 11.891(21) Å, c = 6.934(12) Å, β = 91.56(18)°. The crystal structure of this compound has been determined by a single crystal X-ray diffraction study. Of the total of 2023 reflections measured by a scintillation counter technique, 1107 showed intensities significantly different from background, and the structure has been refined with these to a weighted R-value of 9.7%. The individual molecules are essentially planar with a trapezoid of donor nitrogen atoms at average distances of 1.828 and 1.939 Å from the metal. The crystal contains stacked columns of parallel molecules in which each nickel experiences two very weak intermolecular Ni … N interactions at 3.48 Å roughly normal to the molecular plane. The molecules depart from C 2v symmetry, apparently because of packing effects and intermolecular interactions. The patterns of bond distances in the two halves of the ligand are indicative of considerable electron delocalization in each. The delocalized halves are separated by a CC bridge bond of length 1.53 Å. Although [Ni(BDPH)2H] has been shown to be the central member of a five-membered electron transfer series, the observed bond distances do not indicate that a simple valence bond description of the ground state electronic structure, propose for other electron transfer complexes of equivalent oxidation level, is applicable to this molecule, at least the crystalline state.