Synthesis and Characterization of Homoleptic and Heteroleptic Complexes Involving Dithiocarbamates, Triphenylphosphine, and Nickel(II)

Six new nickel complexes of two dithiocarbamate ligands (cyfdtc=N-cyclohexyl-N- furfuryldithiocarbamate and bztpedtc=N-benzyl-N-[2-thiophenylethyl]dithiocarbamate) namely, (Ni[cyfdtc](2)) (1), (Ni[bztpedtc](2)) (2), (Ni[cyfdtc][NCS][PPh3]) (3), (Ni[bztpedtc] [NCS][PPh3]) (4), (Ni[cyfdtc][PPh3](2))ClO4 (5), and (Ni[bztpedtc][PPh3](2))ClO4 (6) have been prepared and characterized using IR, electronic, and NMR (H-1 and C-13) spectra. A single crystal X-ray structural analysis was carried out for complex 3 and showed that nickel is in a distorted square planar arrangement with the NiS2PN chromophore. The shift in (CN) of the heteroleptic complexes to higher frequencies compared with the parent complex is assigned to mesomeric delocalization of electron density from the dithiocarbamate ligand toward the metal atom, which increases the contribution of polar thioureide form in mixed ligand complexes. Electronic spectral studies suggest square planar geometry for the complexes. In the C-13 NMR spectra, the upfield shift of NCS2 carbon signal for 3 and 4 from the chemical shift value of 1 and 2 is due to effect of PPh3 on the mesomeric drift of electron density toward nickel throughout thioureide CN bond.