Trans effect of triphenylphosphine on Ni–S bonds in solid state and DFT/B3LYP optimized structure: Synthesis, spectral and structural studies on (bis(2-ethylhexyl)dithiocarbamato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II)

GRAPHICAL ABSTRACT

ABSTRACT

The compounds [Ni(behdtc)₂] (1) and [Ni(behdtc)(NCS)(PPh₃)] (2) (where behdtc = bis(2-ethylhexyl)dithiocarbamate) were synthesized and characterized by elemental analyses, electronic, IR, and NMR (¹H and ¹³C) spectroscopy. UV-vis spectral data are consistent with the formation of square-planar nickel complexes. The N¹³CS₂ carbon signal for [Ni(behdtc)(NCS)(PPh₃)] is observed at 204.4 ppm with an upfield shift of about 3.8 ppm compared with that found in [Ni(behdtc)₂] (208.2 ppm). The observed shielding in [Ni(behdtc)(NCS)(PPh₃)] indicates the effect of PPh₃ on the mesomeric drift of electron density toward nickel through the thioureide C-N bond. This observation is supported by the higher νC-N values observed in the IR spectrum of the complex 2. A single crystal X-ray analysis of complex 2 proved four coordinated nickel in a distorted square-planar arrangement with a S₂NP donor set. A significant asymmetry in the Ni–S bond in 2 (2.1690(10) and 2.2234(10)Å) supports the less effective trans effect of SCN⁻ over PPh₃. Molecular electrostatic potential surface map shows that there are no possible sites for nucleophilic attack and S atom of thiocyanate is preferred possible site for electrophilic attack.

KEYWORDS:

• Crystal structure
• theoretical calculations
• dithiocarbamate
• nickel (II) complex