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

Abstract

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 dz ² → dxy/dx ² − y ² transitions. The complexes were diamagnetic. IR and ¹³C NMR studies indicate the mesomeric flow of π-electron density from the dithiocarbamate towards the nickel. In ¹H NMR, α-CH₂–and β-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.

Keywords:

• Nickel
• Dithiocarbamate
• Triphenylphosphine
• dppe
• X-ray crystallography
• NMR