Isonitrosopropiophenone as an ambidentate chelating agent in some transition metal complexes

Abstract

Isonitrosopropiophenonates of cobalt(III), cobalt(II), nickel(II) and palladium(II) have been synthesised and characterised. Isonitrosopropiophenonatonickel(II) exists as green and brown varieties, the green forming mono- as well as bispyridine adducts. The brown variety is obtained after removal of base from the adducts. I.r. data of the metal chelates suggest atrans-asymmetric structure involving N and O bonding for one form and atrans-symmetric structure involving either N or O bonding of the oximino-group for the other. The former is observed exclusively with isonitrosopropiophenonates of nickel(II) while the latter is common among the other metal chelates. The low magnetic moment of the mono-adduct is ascribed to super-exchange interaction between two metal ions through oxo-bridges in the dimer. Acis-octahedral structure has been assigned to the tris(isonitrosopropiophenonato) cobalt(III) on the basis of1H n.m.r. data. Isonitrosopropiophenone forms mixed-ligand complexes of cobalt(III) with tetradentate Schiff bases such as SALEN,N,N′-ethylenebis(salicylaldimine), and SALPN,N,N′-1,3-propylenebis-(salicylaldimine), where the isonitrose group bonds through the nitrogen atom. These complexes have a N,N,N,O,O,O ligand environment. The imino-nickel(II) and -palladium(II) complexes are assigned atrans-symmetric square planar structure. Characterisation of the complexes was based upon elemental analyses, conductivity and magnetic moment, and i.r.,1H n.m.r., and electronic spectra.