Trans influences of Cl-, NCO- and NCS- donors on planar NiS2PN(CO), NiS2PN(CS), NiS2PCl and NiS2P2 chromophores: synthesis, NMR spectral and single crystal X-ray structural studies

Planar [Ni(bedtc)(PPh3)Cl] (1), [Ni(bedtc)(PPh3)(NCO)] (2), [Ni(bedtc)(PPh3)(NCS)] (3), [Ni(bedtc)(PPh3)(CN)] (4) and [Ni(bedtc)(dppe)]ClO4 (5) (where bedtc = N-benzyl-N-(2-hydroxyethyl)dithiocarbamate anion, PPh3 = triphenylphosphine and dppe = 1,2-bis((diphenylphosphino)ethane)) were prepared from [Ni(bedtc)2]. Complexes 1-5 were characterized by elemental analysis, electronic, IR and NMR (1H, 13C, and 31P) spectra. Electronic spectra of the complexes show bands corresponding to dz2 dxy/dx2 - y2 transitions. The complexes were diamagnetic. IR and 13C NMR studies indicate the mesomeric flow of -electron density from the dithiocarbamate towards the nickel. In 1H NMR, -CH2-and -CH2-protons of-CH2-CH2-OH were equally deshielded. The deshielding for the coordinated phosphorus signals in 31P NMR spectra for all the cases compared with the free phosphine clearly manifests the drift of electron density from the phosphorus toward the metal on complexation. Single crystal X-ray structures of 1-3 indicate that nickel is in a planar environment with short S2C-N bond distances. In 2, a rare mode of coordination between nickel and cyanate (NCO-) through the nitrogen is observed. Significant asymmetry in Ni-S bond distances were observed for 1-3 clearly supporting the trans influences of Cl-, NCO- and NCS-, respectively, over PPh3.