Linear Chain Bis(α,β-dionedioximato)metal Compounds of the Nickel Triad: Solid State Design by Molecular Engineering

Abstract

<jats:p>Chemical and structural data of numerous bis(α,β-dionedioximato)metal(II) compounds are summarized. All of them crystallize in columns but principally two different kinds of molecular arrangements occur in the solids. In one phase the molecular planes are inclined to the direction of the linear metal chains with an angle different from 90°. This allows only indirect interactions between the metal ions via the ligand. (“M—L—M” stacking.) The other modification consists of molecules with their planes perpendicular to the M—M-chains. This form allows direct metal-metal contacts (“M—M” modification). Depending on a few molecular parameters a “M—L—M” or a “M—M” stacking is obtained upon crystallization. Since for those compounds which could be isolated in both modifications the M—L—M form has the higher density it is concluded that only stronger M—M interactions stabilize the less dense M—M forms.</jats:p><jats:p>A wide range of metal-metal separations with a lower limit of 3.15 Å in mixed valence systems are found in different “M—M” compounds. In any case the intrachain metal-metal distances are reduced considerably upon oxidation of the bivalent complex molecules. The influence of “electronic” and “sterical” parameters of the complex molecules on the intermolecular metal interactions and on the type of columns in the solid state is discussed.</jats:p>

The crystal and molecular structure of anilinebis(difluoroborondimethylglyoximato)nickel(II)

“…Intermolecular contact distances are comparable with those found in the parent structure (Stephens & Vagg, 1977a). In particular the shorter C... O contacts (Table 4) are similar to those in the parent, which average 3-16 (2) /L It has been suggested (Endres et aL, 1977) that close packing of the organic ligands in these types of complexes occurs at a spacing of about 3-2 A.…”

“…This effect might be expected with the increase in electron density on the Ni atoms, and consequent increase in repulsive forces, that results from the base coordination (Endres et al, 1977).…”

Bis(oxamide onmato)platinum(II)–1/3-sodium acetate–1/3-sodium chloride–2-water

“…There should be only van der Waals interactions between these molecules. Their relative orientation is typical for the M--L--M form of n,fl-dione dioximato complexes of the Ni triad (Endres, Keller, Lehmann, Poveda, Rupp & van de Sand, 1977). Thus, the two characteristic overlap patterns of the two forms of a,fl-dione dioximato complexes of the Ni triad are realized in this compound.…”

“…Poveda, Rupp & van de Sand, 1977). A quite unusual feature is the additional linkage of the molecules within a triad by short 0(2)-0(3) distances [2.60 (2) A], typical for a H bridge.…”

“…In the search for new materials with highly anisotropic physical properties we are interested in the oaoH complexes of the Ni triad (Endres, 1978(Endres, , 1979a, for the a,fl-dione dioximato complexes of these metals are known to crystallize in stacked structures (Endres, Keller, Lehmann, Poveda, Rupp & van de Sand, 1977).…”