Quantification of distortions associated with planar NiS4, NiS2NP and NiS2P2 chromophores: Synthesis, structural and CSM analysis

Abstract

Planar, diamagnetic [Ni(dadtc)(PPh3)(NCS)] (1), [Ni(dadtc)(PPh3)2]ClO4 (2) and [Ni(dadtc)(dppb)]ClO4 (3) (where dadtc=diallyldithiocarbamate, PPh3=triphenyl phosphine, NCS=thiocyanate and dppb=(1,4-bis(diphenylphosphino)butane) have been synthesized and characterized by UV–vis, IR, 1H, 13C, 31P NMR, CV, and thermal analysis. Solvothermal decomposition of the compounds yielded NiS. 1H NMR signals showed the α-CH2 protons to be the highly deshielded and 13C NMR spectra showed the characteristic thioureide (N13CS2) carbon signals around 200ppm. 31P chemical shifts showed the following order: (2) (29.4ppm)>(3) (22.40ppm)>(1) (12.7ppm). Single crystal X-ray analysis of (1), (2) and (3) showed a distorted square planar coordination in the NiS2NP and NiS2P2 chromophores. Deviation of the chromophore from square planar geometry towards tetrahedral geometry has been assessed for the first time by Continuous Symmetry Measure calculation in a scale of ‘0’ to ‘100’, which showed the following decreasing order from planarity: NiS4 (0.894)≫NiS2P2 (0.660)>NiS2NP (0.615)>NiS2P2 (chelating dppb) (0.411). The CSM analysis reveals that the deviation from planarity is less than unity for all the chromophores. However, NiS2P2 (chelating dppb) shows relatively the lowest deviation indicating chelate induced stability.