名称:
Effect of position of methyl substituent in piperidinedithiocarbamate on the ZnS4N chromophore: Synthesis, spectral, valence-bond parameters and single crystal X-ray structural studies on bis(2-methylpiperidinecarbodithioato-S,S′)-(pyridine)zinc(II) and bis(4-methylpiperidinecarbodithioato-S,S′)(pyridine)zinc(II)
摘要:
Two Zn(II)monomethyl substituted piperidinedithiocarbamates with ZnS4N chromophores have been synthesized ([Zn(2-mpipdtc)(2)(py)] (1) and [Zn(4-mpipdtc)(2)(py)] (2) (where 2-mpipdtc = 2-methylpiperidinedithiocarbamate, 4-mpipdtc = 4-methylpiperidinedithiocarbamate and py = pyridine)) from [Zn(2-mpipdtc)(2)] and [Zn(4-mpipdtc)(2)], respectively. Their structures and properties have been characterized by IR, H-1 and C-13 NMR spectroscopy. The structures of both the complexes were determined by single crystal X-ray crystallography. IR spectra of the complexes 1 and 2 show the thioureide nu(C-N) band at 1431 and 1445 cm (1), respectively. In the case of complex 1, the thioureide nu(C-N) values are shifted to lower wave number compared to 2. This may be due to the steric effect of the ortho-methyl group in the 2-mpipdtc resulting in a decrease in the double bond character of the C-N bond. The methyl protons are more deshielded in 1 (1.28 ppm) than that found in 2 (0.98 ppm), due to deshielding decrease with increase in distance from the metal centre. The C-13 NMR peaks of the group (NCS2)-C-13 are found in both cases, at around 202 ppm, which indicates the bidentate character of the ligands. Single crystal X-ray structural analysis of 1 and 2 showed that the zinc atom is pentacoordinated with four sulfur atoms from the dithiocarbamate and one nitrogen atom from the pyridine. Both the complexes adopt a geometry which is intermediate between the tetragonal pyramid (C-4v) and trigonal bipyramid (D-3h). From the tau values, the coordination geometry of 1 and 2 is described as being 38.9% and 36.1% along the pathway of distortion from tetragonal pyramid toward trigonal bipyramid. (C) 2009 Elsevier B. V. All rights reserved.