The Crystal Structure of [2,6-Bis(1-methyl-4-methylthio-5-thia-2,3-diazahexa-1,3-dienyl)-pyridine]dithiocyanatonickel(II), a Complex of a Potentially Pentadentate N₃S₂ Ligand, and a Comparison with Complexes of an N₃O₂ Ligand

Abstract

The crystal structure of Ni(dapsm)(NCS)₂ [dapsm is 2,6-bis(1-methyl-4-methylthio-5-thia-2,3-diazahexa-1,3-dienyl)pyridinel has been determined from three-dimensional single-crystal diffractometer X-ray data. Structure refinement was carried out by least-squares methods to a final R value of 0.059. The ligand dapsm is a potential N₃S₂ pentadentate, but it coordinates as a tetradentate, giving a planar N₃S donor grouping. Rotation occurs about an N-N bond in dapsm, moving a potential donor sulfur atom away from the nickel(II) ion. The pyridine ring of the ligand, and the N₃S donor grouping, are approximately coplanar. Two thiocyanate groups are coordinated to the nickel, giving a distorted octahedral structure. The structure and electronic spectrum of Ni(dapsm)- (NCS)₂ are compared with those for seven-coordinate complexes with the related N₃O₂ ligand, 2,6-diacetylpyridine bissemicarbazone.