Synthesis and spectroscopic characterization of Ni(II) complexes involving functionalised dithiocarbamates and triphenylphosphine: Anagostic interaction in (N-cyclopropyl-N-(4-fluorobenzyl)dithiocarbamato-S,S′) (thiocyanato-N)(triphenylphosphine)nickel(II)

Abstract

Twelve new nickel(II) complexes namely [Ni(S2CNRR′)2](1–6) and [Ni(S2CNRR′)(NCS)(PPh3)](7–12) [where R = cyclopropyl (cPr); R′ = 2HO–C6H4–CH2– (1,7), 3HO–C6H4–CH2– (2,8), 4HO–C6H4–CH2– (3,9), 4CH3O–C6H4–CH2– (4,10), 4F–C6H4–CH2– (5,11), 4Cl–C6H4–CH2– (6,12)] have been prepared and characterized by elemental analysis, IR, UV–Vis and NMR (1H and 13C) spectroscopy. A single crystal X-ray structural analysis was carried out for (N-cyclopropyl-N-(4-fluorobenzyl)dithiocarbamato-S,S′)(thiocyanato-N)- (triphenylphosphine)nickel(II). The increase in wavenumber of νC–N thioureide and decrease in chemical shift values of heteroleptic complexes 7–12 compared to that of homoleptic complexes 1–6 are due to the mesomeric drift of electron density from the dithiocarbamate moiety towards the metal centre, increasing the carbon–nitrogen double bond character. The increased strength of C–N bond is due to the presence of the π-accepting triphenylphosphine. Electronic spectral studies indicated square planar geometry around the nickel(II) central atom for all the complexes. Single crystal X-ray structural analysis of 11 confirms that the coordination geometry about the Ni is distorted square planar. The C–H…F interactions lead to a polymeric structure and a rare intramolecular anagostic interaction [M…H = 2.929 Å] is observed. The molecular geometry, HOMO–LUMO in the ground state and MEP have been calculated for 11 using the Hartree–Fock (HF) method with the LANL2DZ basic set. The optimized bond lengths and bond angles agree well with the experimental results. The asymmetry in the Ni–S bonds reveal the greater trans influence of triphenylphosphine compared to that of the isothiocyanate ion.