Synthesis and spectral studies on Ni(II) complexes involving N-furfuryl-N-substituted benzyldithiocarbamates and PPh₃: Anagostic and C–H^…π(chelate) interactions in (N-furfuryl-N-(4-fluorobenzyl)dithiocarbamato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II)

ABSTRACT

Twelve new nickel(II) complexes of functionalized dithiocarabamates [Ni(S₂CNRR')₂](1-6) and [Ni(S₂CNRR')(NCS)(PPh₃)](7-12) [where R=furfuryl; R'=2-hydroxy benzyl (1,7), 3-hydroxy benzyl (2,8), 4-hydroxy benzyl (3,9), 4-methoxy benzyl (4,10), 4-fluoro benzyl (5,11), 4-chloro benzyl (6,12)] have been prepared and characterized by elemental analysis, IR, UV-Vis and NMR (¹H and ¹³C) spectroscopy. IR spectra of the complexes support the bidentate coordination of dithiocarbamate ligands. Electronic spectral studies on complexes 1-12 indicate square planar geometry around the nickel(II) central atom. In the ¹³C NMR spectra, the upfield shift of NCS₂ carbon signal for heteroleptic complex (7-12) compared to homoleptic complexes (1-6) is due to the effect of PPh₃ on the mesomeric drift of electron density toward nickel through thioureide C-N bond. Single crystal X-ray structural analysis of complex 11 confirms that the coordination geometry about the Ni(II) is distorted square planar. A rare intramolecular anagostic interaction C–H^…Ni [Ni⋅⋅⋅H=2.804 Å] is observed. The packing of complex 11 is stabilized by non-conventional C–H^…S, C–H⋯F and C–H⋯π(chelate, NiS₂C) bonding interactions.

GRAPHICAL ABSTRACT

KEYWORDS:

• Ni(II) dithiocarbamate
• NMR spectroscopy
• X-ray structure
• anagostic interaction

Funding

E. Sathiyaraj gratefully acknowledges the University Grants Commission (UGC), India, for the award of Basic Sciences Research (BSR)-Special Assistant Programme (SAP) Fellowship.