Metal complexes derived from hydrazoneoxime ligands: III – Synthesis, characterization and electrospray ionization mass spectra of some nickel(II) complexes with aroylhydrazoneoximes

Abstract

Five binuclear nickel(II) complexes [{Ni(L-R)} 2] derived from diacetylmonooxime aroylhydrazones (H 2L-R) have been prepared and characterized. In these complexes the oximate group functions as a bridge between the two nickel(II) ions. The corresponding octahedral bisligand complexes [Ni(HL-R) 2] have been also prepared and characterized. Reaction of [{Ni(L-R)} 2] with excess pyrazole (HPyr) afforded square planar [Ni(L-R)HPyr] complexes. The structure of [Ni(L-H)HPyr] ( 11), [Ni(L-CH 3O)HPyr] ( 13) and [Ni(L-Cl)HPyr] ( 14) have been determined by single-crystal X-ray diffraction. In these complexes, the Ni(II) is coordinated to the oximate nitrogen, hydrazone nitrogen and enolimine oxygen of the aroylhydrazoneoxime ligand, the fourth coordination site is occupied by pyrazole nitrogen. In 11 and 13 the molecular units are linked together by intramolecular NH⋯O hydrogen bonds forming a helical chain propagating along a and b axis respectively. The helical structure is stabilized by CH⋯O, CH⋯π and π⋯π noncovalent interactions. The structure of 14 consists of two independently crystallographic molecular units. The Ni1 molecular units are assembled together by CH⋯O and CH⋯Cl1 interactions forming a two dimensional sheet, while the Ni2 units are jointed together by CH⋯O and CH⋯C interactions forming a chain extending along b-axis which are enclosed between sheets of Ni1 units.