Trinudear Molecules in the Crystal Structure of Bisacetylacetonenickel(II)

Abstract

THE stereochemistry of four-covalent nickel(II) complexes has been a subject of great interest to chemists for the past two decades. Following the enunciation of Pauling's theories relating stereochemistry, bonding orbitals and magnetic moment, it has been shown that, in all cases where structural studies have been carried out, the diamagnetic four-covalent complexes of nickel(II) are square planar¹. However, little work has been done to investigate the structure of the paramagnetic (presumably) four-covalent complexes such as bissalicylaldehyde-nickel(II) and bisacetylacetonenickel(II). These complexes have a magnetic moment indicating two unpaired electrons² and usually this has been assumed, without proof, to indicate that 4_s ${\text{4}}_{p^{\text{3}}}$ tetrahedral bonding occurs. It has been shown by Curtiss, Lyle and Lingafelter³ that the X-ray powder patterns of bissalicylaldehydenickel(II) and of its zinc analogue are identical. This has been taken as evidence in support of a tetrahedral arrangement of the four oxygen atoms around the nickel(II) atom because zinc(II) is known to display tetrahedral co-ordination. However, in the absence of definite proof that the zinc(II) atom has tetrahedral co-ordination in this instance, the case is not proved. It was decided, therefore, to carry out an X-ray investigation of bisacetylacetonenickel(II) and the preliminary results are summarized here.