A. Lyubchova et al., Structure of di(salicylaldehyde benzoylhydrazonato) zinc(II), an unusual staircase polymeric structure formed via E -> Z isomerization on complexation, Z KRISTALL, 216(10), 2001, pp. 556-559
A bicomplex of salicylaldehyde benzoylhydrazone (SBH) with Zn(II) was synth
esized in ethanol and single crystals were obtained in DMSO. The compound c
rystallizes in the orthorhombic system with the space group Pna2(1)(33) and
crystal data: a = 22.573(3) A, b = 6.1208(5) A. c = 17.881(2) A. V = 2470.
5(5) A(3). Z = 4. d(calc) = 1.462 g(.)cm(-3). (2633 reflections with I > 2
sigma (I); final R = 0.0509: R-w = 0. 1099).
The asymmetric unit is a nearly planar bicomplex built up from one Zn atom
linked to two monodeprotonated SBH ligands. The compound can be described a
s formed of chains extended along the b axis. This linear polymeric charact
er results from the linking of each asymmetric unit to two neighbouring one
s via four (2 x 2) covalent Zn-O bonds involving three Zn atoms and four ph
enolic oxygens. These covalent bonds are related to the very unusual Z conf
iguration of the ligand. The three-dimensional cohesion of the compound is
obtained by van der Waals forces between the polymeric chains. El Hage Chah
ine. 1997). The title compound was prepared and characterized as a part of
this work.
In other respects, metal cations were classified as hard and soft Lewis aci
d - HSAB concept (Pearson, 1963). Soft acids form unexpected complexes with
Lewis bases. Therefore, it seemed interesting to study the behavior of a c
helator designed as a hard and/or a borderline Lewis base towards complex f
ormation with a borderline Lewis acid, Zn++.