Synthesis and characterization of mercury(II) complexes with 2,6-diacetylpyridine bis[N-methyl-N-(2′-pyridyl)hydrazone]. X-Ray structure of chloro{2,6-diacetylpyridine bis[N-methyl-N-(2′-pyridyl)hydrazone]}-mercury(II)–hexachlorodimercurate(II)(2/1)

Abstract

The quinquedentate ligand 2,6-diacetylpyridine bis[N-methyl-N-(2′-pyridyl)hydrazone], (dapmp) reacts in ethanol with Hg(NO₃)₂·H₂O in the presence of perchlorate ions to give the seven-co-ordinate diaqua complex [Hg (dapmp)(H₂O)₂][ClO₄]₂(1), while starting from HgCl₂ the species [Hg(dapmp)Cl]·0.5[Hg₂Cl₆](2) is obtained. The complexes have been characterized by a number of physicochemical measurements including the X-ray analysis of (2). Crystals of (2) are monoclinic, space group P2₁/c, with unit-cell dimensions a= 12.081 (2), b= 10.295(2), c= 21.480(2)Å, β= 93.00(1)°, and Z= 4. The structure has been solved from three-dimensional counter data by Patterson and Fourier methods and refined by full-matrix least squares to R 0.037 for 3 350 observed reflections. The crystal consists of a packing of discrete units of [Hg(dapmp)Cl]⁺ cations and [Hg₂Cl₆]^2– anions in the ratio 2 : 1. The co-ordination in the cation is approximately pentagonal pyramidal; the five basal positions are occupied by five N atoms of the polydentate ligand with a remarkable helical distortion and the apical position by a Cl atom which makes an angle of 10.3(1)° with the normal to the mean plane passing through the co-ordinated N atoms. The Hg atom lies 0.51 Å over this plane in the Cl direction.