Author:
Finney AJ,Hitchman MA,Raston CL,Rowbottom GL,White AH
Abstract
The crystal structures of
the dimer [Ni(γmpy)2(NO2)2]2,2C6H6
and the trimer [Ni(βmpy)2(NO2)2]3,-
C6Hs (γmpy = 4-methylpyridine,
βmpy = 3-methylpyridine) are reported, the
latter being the redetermination of a structure
described previously. The ligand coordination geometry in each oligomer is essentially octahedral, with neighbouring nickel(II) ions being bridged by two nitrite
groups, one through a single oxygen atom and the second through an oxygen and
the nitrogen atom. The amine ligands occupy trans coordination sites with the
terminal bond positions in both species being taken up by chelating nitrite
ions. In both compounds the oligomers pack so that
the amine rings form sheets with potential voids in the lattice being filled by
clathrated benzene molecules. The electronic spectra
of the complexes in the visible region are unusual, showing peaks centred at c. 17500 and c. 20500 cm-1, and the
assignment of these is discussed. The infrared stretching frequencies of the
nitrite groups in these and other compounds are found to correlate well with
the observed nitrogen-oxygen bond lengths.