Synthesis, NMR spectral and single crystal X-ray structural studies on Ni(II) dithiocarbamates with NiS2PN, NiS2PC, NiS2P2 chromophores: Crystal structures of (4-methylpiperazinecarbodithioato)(thiocyanato-N) (triphenylphosphine)nickel(II) and bis(triphen

Four Ni(II) dithiocarbamates with NiS2PX (X = NCS or CN or P) chromophores have been synthesized [[Ni(4-mpzdtc)(PPh3)(NCS)] (1), [Ni(4-mpzdtc)(PPh3)(CN)] (2), [Ni(4-mpzdtc)(PPh3)2]ClO4 · H2O (3) and [Ni(4-mpzdtc)(dppe)]ClO4 (4) (where 4-mpzdtc = 4-methylpiperazinecarbodithioato anion, PPh3 = triphenylphosphine and dppe = 1,2-bis((diphenylphosphino)ethane))] from [Ni(4-mpzdtc)2]. Electronic spectra of the complexes show bands corresponding to dz2/dxy→dx2-y2dz2/dxy→dx2-y2 transitions. IR spectra of all the compounds showed characteristic bands due to the dithiocarbamate ligand around 1500 cm−1 and 990 cm−1. CV studies showed a higher reduction potential for the parent complex indicating the reluctance to add more electron density to the already electron rich metal centre. 1H NMR spectra of the complexes showed the deshielding of α-CH2 protons on complexation. The 13C signals show interesting variations for the S2–13C N carbon signals between the neutral [1 and 2] and ionic complexes [3 and 4]. The S2–13C N chemical shifts of the three complexes with PPh3 follow the order: 3 < 1 < 2 indicating the influence of PPh3, NCS, CN respectively on the mesomeric drift of electron density towards nickel. The PPh3 complexes show the following order of increasing 31P chemical shifts: 3 (30.9 ppm) > 2 (22.1 ppm) > 1 (20.5 ppm). The observed order clearly establishes the ease with which the back bonding interaction takes place. The back bonding is best observed in the case of the NiS2P2 chromophore. Single crystal X-ray structures of [Ni(4-mpzdtc)(PPh3)(NCS)] and [Ni(4-mpzdtc)(PPh3)2]ClO4 indicate that the central metal atom is in a planar environment for both complexes. The planarity of the molecules is supported by the observed diamagnetism of the complexes. The short S2–C N bonds indicate the partial double bond character in both cases.

Ni(II) Dithiocarbamates with NiS2PN, NiS2PC, NiS2P2 chromophores have been synthesized. 13C signals show interesting variations for the thioureide carbon signals between the neutral [1 and 2] and ionic complexes [3 and 4]. UV–Vis and XRD analyses evidence the square planar geometry around the central metal atom in all the cases.Figure optionsDownload as PowerPoint slide