Trans effect of triphenylphosphine on Ni–S bonds in solid state and DFT/B3LYP optimized structure: Synthesis,spectral and structural studies on (bis(2-ethylhexyl)dithiocarbamato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II)

The compounds [Ni(behdtc)₂] (1) and [Ni(behdtc)(NCS)(PPh₃)] (2) (where behdtc = bis(2-ethylhexyl)dithiocarbamate) were synthesized and characterized by elemental analyses, electronic, IR, and NMR (¹H and ¹³C) spectroscopy. UV-vis spectral data are consistent with the formation of square-planar nickel complexes. The N¹³CS₂ carbon signal for [Ni(behdtc)(NCS)(PPh₃)] is observed at 204.4 ppm with an upfield shift of about 3.8 ppm compared with that found in [Ni(behdtc)₂] (208.2 ppm). The observed shielding in [Ni(behdtc)(NCS)(PPh₃)] indicates the effect of PPh₃ on the mesomeric drift of electron density toward nickel through the thioureide C-N bond. This observation is supported by the higher νC-N values observed in the IR spectrum of the complex 2. A single crystal X-ray analysis of complex 2 proved four coordinated nickel in a distorted square-planar arrangement with a S₂NP donor set. A significant asymmetry in the Ni–S bond in 2 (2.1690(10) and 2.2234(10)Å) supports the less effective trans effect of SCN^? over PPh₃. Molecular electrostatic potential surface map shows that there are no possible sites for nucleophilic attack and S atom of thiocyanate is preferred possible site for electrophilic attack.     

Synthesis and spectral studies on NiS<Subscript>4</Subscript>, NiS<Subscript>2</Subscript>PN,NiS<Subscript>2</Subscript>P<Subscript>2</Subscript> chromophores: Single-crystal X-ray structure of [Ni(dbpdtc)<Subscript>2</Subscript>] (dbpdtc = benzyl(4-(benzylamino)phenyl)dithiocarbamate)

Three complexes of a dithiocarbamate ligand (dbpdtc = benzyl(4-(benzylamino)phenyl)dithiocarbamate), namely [Ni(dbpdtc)₂] (1), [Ni(dbpdtc)(NCS)(PPh₃)] (2) and [Ni(dbpdtc)(PPh₃)₂]ClO₄ (3) have been prepared. The complexes were characterized by IR, electronic spectroscopy and cyclic voltammetry. A single-crystal X-ray structural analysis was carried out for complex 1 and showed that the nickel is in a distorted square planar environment with a NiS₄ chromophore. For the two mixed ligand complexes, the thioureide ν _C–N values were shifted to higher wavenumbers compared to [Ni(dbpdtc)₂], suggesting increased strength of the thioureide bond due to the presence of the π-accepting phosphine. Electronic spectral studies suggest square planar geometries for the complexes. Cyclic voltammetry showed easier reduction of nickel(II) to nickel(I) in the mixed ligand complexes compared to [Ni(dbpdtc)₂].     

Synthesis,Spectral, Cyclic Voltammetric Studies,and Single Crystal X‐Ray Structure Determination of the Planar NiS2P2, NiS2PN,and NiS2PC Chromophores

Synthesis, spectral and cyclic voltammetric characterization of [Ni(dedtc)(4‐MP)₂](ClO₄) ( 1 ), [Ni(dedtc)(4‐MP)(NCS)]( 2 ), [Ni(dedtc)(PPh₃)(NCS)] ( 3 ) and [Ni(dedtc)(PPh₃)(CN)] ( 4 ) (dedtc = diethyldithiocarbamate, 4‐MP = tri(4‐methylphenyl)phosphine, PPh₃ = triphenylphophine) are reported. IR spectra of complexes 1‐4 show the characteristic thioureide (C‐N) bands at higher wave numbers compared to that of the parent dithiocarbamate complex [Ni(dedtc)₂]. The d‐d transitions are observed in the region 452—482 nm. The CV studies clearly show the presence of reduced electron density on the nickel ions in mixed ligand complexes 1‐4 compared to the parent dithiocarbamate. Single crystal X‐ray structure studies show all the complexes to containplanar NiS₂P₂, NiS₂PN, and NiS₂PC chromophores in keeping with the observed diamagnetism. In all the complexes the Ni‐S distances are asymmetric. The thioureide C‐N distance of the complexes 1‐4 are less thanthe C‐N distance observed in the parent [Ni(dedtc)₂].     

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 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.     

Steric and electronic effects of N -coordinated NC − and NCS− on NiS2PN: synthesis,spectral and single crystal X-ray structural studies on N,N ′-di- n -butyldithiocarbamate complexes of nickel(II) with phosphorus and nitrogen donor ligands

Planar nickel(II) complexes involving N,N′-dibutyldithiocarbamate, such as [Ni(bu₂dtc)(PPh₃)(NC)] (1) and [Ni(bu₂dtc)(PPh₃)(NCS)] (2) (where bu₂dtc = N,N′-dibutyldithiocarbamate anion) have been prepared, characterized by electronic, IR and NMR spectra and their structures determined by single crystal X-ray crystallography. Cyclic voltammetric characterizations of the complexes are also reported. IR spectra of the two complexes indicate the isobidentate coordination (ν_c-s ? 1095 cm^?1 without splitting) of the dithiocarbamate moiety. The important stretching mode characteristic of the thioureide bond (ν_C–N) occurs at higher wave numbers compared to that of the parent dithiocarbamate complex [Ni(bu₂dtc)₂]. The electronic spectra of 1 and 2 show signature bands at 426 nm and 478 nm, respectively. NMR spectra show large ³¹P chemical shifts in both compounds and the most important N¹³CS₂ chemical shift appears at 204.86 ppm and 203.23 ppm for 1 and 2, respectively. The CV studies clearly show the presence of reduced electron density on the nickel ions in mixed-ligand complexes 1 and 2 compared to the parent dithiocarbamate. Single crystal X-ray structure studies show that 2 crystallizes as a new triclinic polymorph, whose molecular structure closely resembles that of the previously reported monoclinic form. Both complexes contain a planar NiS₂PN chromophore in keeping with the observed diamagnetism. In both complexes the Ni-S distances are significantly different. The thioureide C–N distances of the complexes are shorter than those observed in the parent [Ni(bu₂dtc)₂]. The two compounds allow comparison of the influence of NCS^? in place of NC^?.     

N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamato Complexes of Nickel(II) with Phosphorus Donor Ligands

Planar nickel(II) complexes involving N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamate, such as [NiX(nmedtc)(PPh₃)] (X = Cl, NCS; PPh₃ = triphenylphosphine), and [Ni(nmedtc)(P‐P)]ClO₄(P‐P = 1,1‐bis(diphenylphosphino)methane(dppm); 1,3‐bis(diphenylphosphino)propane (1,3‐dppp); 1,4‐bis(diphenylphosphino)butane(1,4‐dppb) have been synthesized. The complexes have been characterized by elemental analyses, IR and electronic spectroscopies. The increased νC–N value in all the complexes is due to the mesomeric drift of electrons from the dithiocarbamate ligands to the metal atom. Single crystal X‐ray structure of [Ni(nmedtc)(1,3‐dppp)]ClO₄·H₂O is reported. In the present 1,3‐dppp chelate, the P–Ni–P angle is higher than that found in 1,2‐bis(diphenylphosphino)ethane‐nickel chelates and lower than 1,4‐bis(diphenylphosphino)butane‐nickel chelates, as a result of presence of the flexible propyl back bone connecting the two phosphorus atoms of the complex.     

Syntheses,characterization, and antimicrobial properties of nickel(II) dithiocarbamate complexes containing NiS4 and NiS2PN moieties

Three Ni(II) dithiocarbamate complexes, [Ni(buphdtc)₂] (1), [Ni(buphdtc)(PPh₃)(NCS)] (2) and [Ni(buphdtc)(PPh₃)(NC)] (3) (where bu = butyl and ph = phenyl), were synthesized and characterized by elemental analysis, UVvis, and FTIR spectroscopies. Complexes 1 and 2 were further characterized by single-crystal X-ray structural analysis. The single-crystal X-ray structural analysis indicates a slightly distorted square planar geometry. In 2 and 3, the influences of the auxiliary ligands (PPh₃, NCS, and NC) on their steric and electronic properties were observed. Thermal studies of the complexes showed decomposition starting at 250–300 °C, leading to formation of nickel sulfide phases around 400 °C. The complexes were screened against some bacteria strains, Staphylococcus aureus, Streptococcus pneumoniae, Bacillus subtilis, Escherichia coli, Klebsiella oxytoca and Pseudomonas aeruginosa, and two fungi species, Aspergillus niger and Fusarium oxysporum. The complexes showed moderate-to-strong antimicrobial potentials, with [Ni(buphdtc)₂] (1) displaying the best antimicrobial activity. Fluconazole and streptomycin were used as reference drugs for antifungal and antibacterial assays, respectively.     

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)

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.     

Synthesis,Spectral, Valence‐Bond Parameters,and Single Crystal X‐ray Structural Studies on [Ni(dnpdtc)(PPh3)(NCS)] and [Ni(dnpdtc)(PPh3)(CN)]

Two new nickel complexes withplanar surrounding of Ni [Ni(dnpdtc)(PPh₃)(NCS)] (1) and [Ni(dnpdtc)(PPh₃)(CN)] (2) (dnpdtc=N, N‐dipropyldithiocarbamate) were prepared from the parent dithiocarbamate and were characterized by elemental analysis, electronic, IR and NMR spectra. The structures of both the complexes were determined by single crystal X‐ray crystallography. Thioureide stretching vibrations occur at 1528 cm^‐1 and 1521 cm^‐1 for 1 and 2 respectively. Large ³¹P chemical shifts were observed for the two compounds. A significant asymmetry in Ni—S bond distances was observed in compound 1 [2.1700(16) and 2.2251(17)Å] whereas in compound 2 the bond distances were almost similar [2.2100(14) and 2.2122(13)Å]. A marginal difference was observed with respect to the thioureide bond distances [1.340(6)Å for 1 and 1.312(5)Å for 2 ]. The observation clearly supports the less effective trans influence of SCN^— over PPh₃. However, PPh₃ and CN^— show almost similar trans influence.     

Structural variations of nickel complexes in NiS4 and NiS2PN coordination environments: spectral and single-crystal X-ray structural studies on bis(4-methylpiperidinecarbodithioato-S,S′)nickel(II) and (4-methylpiperidinecarbodithioato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II)

Abstract  

[Ni(4-mpipdtc)₂] and [Ni(4-mpipdtc)(PPh₃)(NCS)] (4-mpipdtc = 4-methylpiperidinecarbodithioate anion) have been characterized by electronic, IR, and NMR spectroscopy, single crystal X-ray analysis, and cyclic voltammetry. IR spectra of the complexes show the contribution of the thioureide form to the structures. ¹H NMR spectra show the deshielding of α-CH₂ protons on complexation. ¹³C NMR spectra shows interesting differences between the N¹³CS₂ carbon signals of the parent complex [Ni(4-mpipdtc)₂] and the mixed ligand complex [Ni(4-mpipdtc)(PPh₃)(NCS)]. The N¹³CS₂ carbon signal for [Ni(4-mpipdtc)(PPh₃)(NCS)] is observed at 204.85 ppm with an upfield shift of about 3.8 ppm compared with that found in [Ni(4-mpipdtc)₂] (201.06 ppm). The observed shielding in [Ni(4-mpipdtc)(PPh₃)(NCS)] indicates the effect of PPh₃ on the mesomeric drift of electron density toward nickel through the thioureide C–N bond. Single crystal X-ray analysis of [Ni(4-mpipdtc)₂] and [Ni(4-mpipdtc)(PPh₃)(NCS)] confirms the presence of four-coordinated nickel in a distorted square-planar arrangement with the NiS₄ and NiS₂PN chromophores, respectively. The C–N (thioureide) bond lengths of [Ni(4-mpipdtc)(PPh₃)(NCS)] are shorter than those found in [Ni(4-mpipdtc)₂], because of the presence of the π-acid (triphenylphosphine) in [Ni(4-mpipdtc)(PPh₃)(NCS)]. Significant asymmetry in Ni–S bond distances was observed in Ni(4-mpipdtc)(PPh₃)(NCS)] (2.162(2) and 2.211(2) ?). This observation clearly supports the less effective trans effect of SCN^– over PPh₃. The piperidine ring in the dithiocarbamate fragment is in the normal chair conformation.     

Synthesis,crystal structure,and antibacterial activity of mononuclear nickel(II) and cobalt(III) Schiff-base complexes

Four new mononuclear complexes, [Ni(L¹)(NCS)₂] (1), [Ni(L²)(NCS)₂] (2), [Co(L¹)(N₃)₂]ClO₄ (3), and [Co(L²)(N₃)₂]ClO₄ (4), where L¹ and L² are N,N′-bis[(pyridin-2-yl)methylidene]butane-1,4-diamine and N,N′-bis[(pyridin-2-yl)benzylidene]butane-1,4-diamine, respectively, have been prepared. The syntheses have been achieved by reaction of the respective metal perchlorate with the tetradentate Schiff bases, L¹ and L², in presence of thiocyanate (for 1 and 2) or azide (for 3 and 4). The complexes have been characterized by microanalytical, spectroscopic, single crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1–4 are distorted octahedral geometries. The antibacterial activity of all the complexes and their constituent Schiff bases have been tested against Gram-positive and Gram-negative bacteria.     

Steric distortion of planar NiP<Subscript>2</Subscript>N<Subscript>2</Subscript> chromophores: a spectral,cyclic voltammetric and single crystal X-ray structural study

The complexes trans-[Ni(4-MP)₂(NCS)₂]·MeCN (1) and trans-[Ni(3-MP)₂(NCS)₂] (2) (4-MP = tri(4-methylphenyl)phosphine, 3-MP = tri(3-methylphenyl)phosphine) were prepared and characterized by IR, UV–visible, NMR spectra, CV, TGA and single crystal X-ray crystallography. Both the complexes have planar geometry and are diamagnetic. The Ni–P distances in both complexes are relatively short as a result of strong back donation from nickel to phosphorus. The phenyl rings in the 3-MP analogue (2) show increased pitching with reference to the plane formed by the ipso carbons due to increased steric effects. For complex (2), the N–Ni–N and P–Ni–P angles are significantly lower than the almost linear N–Ni–N and N–Ni–P angles observed for both complex (1) and trans-[Ni(PPh₃)₂(NCS)₂]. This observation indicates that the 3-methylphosphine ligand forces complex (2) to distort towards a tetrahedral geometry. IR spectra of both complexes show strong bands around 2,090 cm⁻¹ due to N-coordinated thiocyanate, while the electronic spectra contain d–d transitions around 452 nm. Cyclic voltammograms show that the irreversible one-electron reduction potentials increase in the following order: trans- [Ni(PPh₃)₂(NCS)₂] < trans- [Ni(3-MP)₂(NCS)₂] < trans-[Ni(4-MP)₂(NCS)₂], revealing the electron releasing effect of the methyl groups. The planar complexes exhibit interallogony in coordinating solvents.     

Nickel(II) di(pentyl)dithiocarbamates with P ligands

Ni(II) di(pentyl)dithiocarbamates of composition [Ni(Pe₂dtc)₂], [NiX(Pe₂dtc)(PPh₃)] (X = Cl, Br, I, NCS), [Ni(NCS)(Pe₂dtc)(PBut₃)], [Ni(Pe₂dtc)(PPh₃)₂]ClO₄ and [Ni(Pe₂dtc)(PPh₃)₂]PF₆ (Pe₂dtc = di(pentyl)dithio-carbamate, PPh₃ = triphenylphosphine, PBut₃ = tributylphosphine) have been synthesized. The complexes have been characterized by the usual methods. X-ray structure analyses confirmed the nature of [NiI(Pe₂dtc)(PPh₃)] and [Ni(Pe₂dtc)(PPh₃)₂]ClO₄ complexes.     

Synthesis,characterization, and antitumor properties of ruthenium(II) anthraquinone complexes

Three new Ru(II) complexes, [Ru(dmb)₂(ipad)](ClO₄)₂ (dmb = 4,4′-dimethyl-2,2′-bipyridine, ipad = 2-(anthracene-9,10-dione-2-yl) imidazo[4,5-f][1,10]phenanthroline, 1), [Ru(dmp)₂(ipad)](ClO₄)₂ (dmp = 2,9-dimethyl-1,10-phenanthroline, 2), and [Ru(dip)₂(ipad)](ClO₄)₂ (dip = 4,7-diphenyl-1,10-phenanthroline, 3), have been synthesized and characterized. The three Ru(II) complexes intercalate with the base pairs of DNA. The in vitro antiproliferative activities and apoptosis-inducing characteristics of these complexes were investigated. The complexes exhibited cytotoxicity against various human cancer cell lines. BEL-7402 cells displayed the highest sensitivity to 1, accounted for by the greatest cellular uptake. Complex 1 was shown to accumulate preferentially in the nuclei of BEL-7402 cells and cause DNA damage and induce apoptosis, which involved cell cycle arrest and reactive oxygen species generation.     

Komplexbildung mit Aminophosphinen. IX. Vier- und fünffach koordinierte Komplexverbindungen des Nickels mit N,N-Bis(diphenylphosphino)anilin

Complex Formation with Aminophosphines. IX. Fourfold and Fivefold Coordinated Nickel(II) Complexes of the Bidentate N, N-Bis(diphenylphosphino)phenylamine The preparation and characterization of the ligand PhN(PPh₂)₂ and some of its nickel complexes are reported. The ligand (NP₂) forms stable planar complexes [(NP₂)NiX₂] (X = Cl, Br, I, NCS) and [Ni(NP₂)₂](ClO₄)₂, and the pentacoordinated, square-pyramidal complexes [(NP₂)₂NiX]ClO₄.     

Sodium-mediated self-assembly of two nickel(II) Schiff base complexes: crystal structure and characterizations

Sodium-assisted self-assembly of two nickel(II) Schiff base complexes under similar reaction conditions yield hetero-metallic compounds [{Ni(salpn)}₂Na(ClO₄)] (1) and [{Ni(salpr)}₃Na][Ni(salpr)]₂ClO₄·2H₂O (2) (where salpn?=?N,N′-bis-(salicylidene)-1,3-diaminopropane and salpr?=?N,N′-bis-(salicylidene)-1,2-diaminopropane). Both have been characterized by physico-chemical techniques and single-crystal X-ray diffraction. Crystal structure reveals that in the tri-metallic system of 1 sodium is sandwiched between two [Ni(salpn)] units while the hexametallic system of 2 consists of tetrametallic cluster ion [{Ni(salpr)}₃Na]⁺ with encapsulated sodium by three [Ni(salpr)] units. In both complexes, sodium adopts distorted trigonal prismatic geometry leaving nickel(II) in a distorted square-planar environment. Structural characterization also reveals that 2?:?1 (for 1) and 3?:?1 (for 2) self-assemblies of metallo-ligand and sodium were achieved with slight variation in ligand backbone.     

Copper(II), nickel(II) and zinc(II) complexes ofN,N′, N″, N‴-tetra(2-cyanoethyl)-1,4,8, 12-tetra-azacyclopentadecane

Summary Reaction of 1,4,8, 12-tetra-azacyclopentadecance ([15])-aneN₄) with an excess of acrylonitrile gives theN-tetracyanoethylated ligand (L). Several new complexes of this ligand with nickel(II), copper(II) and zinc(II) have been prepared and characterised. The complexes can be formulated [NiL]_n(ClO₄)_2n, [ML](ClO₄)₂ (M=Cu^II and Zn^II), [NiL(NCS)₂], [NiLCl₂], [CuL](NO₃)₂ and [NiL]_n(NO₃)_2n·2H₂O. Spectral, magnetic and conductivity data are reported and possible structures are considered.     

Trans influence of triphenylphosphines and pseudohalogens on Ni-S bonds: Synthesis, spectral and single crystal X-ray structural studies on NiS2PN and NiS2PC chromophores

Trans influence of triphenylphosphines and pseudohalogens on Ni-S bonds of NiS₂PN and NiS₂PC chromophores has been investigated by synthesizing and characterizing them. The complexes show the characteristic thioureide IR band at ∼ 1530 cm⁻¹. Electronic spectrum of the cyanide analogue shows a strong blue shift relative to others. X-ray structures of [Ni(pipdtc)(4-MP)(NCS)] (1), [Ni(pipdtc)(PPh₃)(NCS)] (2) and [Ni(pipdtc)(PPh₃)(CN)] (3) (pipdtc = piperidinecarbodithioate anion, 4-MP = tri(4-methylphenyl)phopshine) are reported. Ni-S bond distance trans to 4-MP(1) is longer than the distances in (2) and (3) and Ni-S bond distances trans to Ni-NCS/CN decrease as follows: (3) > (2) > (1). Particularly, 4-MP shows a highly significant trans influence than triphenylphosphine on Ni-S bond. Similarly, CN⁻ exerts a marginally significant trans influence compared to NCS-. Thioureide C-N distances are relatively very short due to the drift of electron density towards the metal. The Ni-N-C angle (163.5(2)°) observed in (2) indicates deviation from linearity to a larger extent compared to that in (1) (176.3(3)°) due to the steric effect of the 4-methyl group. The reduction potentials (CV) for the mixed ligand complexes are much less compared to that of the parent NiS₄ chromophore due to the π-acidic phosphines.      

Three new homoleptic nickel(II) 1,1-dithiocarbamate complexes: synthesis,structure, electrical conductivity and DFT study

Abstract

Three new homoleptic complexes of nickel having the formula [Ni(L1)₂] [L1?=?C₁₄H₁₄N₁O₂S₂^-, N-(4-methoxybenzyl)(furfuryl)methane dithiocarbamate] (1), [Ni(L2)₂] [L2?=?C₁₇H₁₈N₁O₂S₂^–, N-bis(4-methoxybenzyl)methane dithiocarbamate] (2) and [Ni(L3)₂] [L3?=?C₁₉H₂₁N₁O₁S₂^-, N-(4-isopropylbenzyl)(4-methoxybenzyl)methane dithiocarbamate] (3), have been designed, synthesized, and characterized by elemental analysis, IR, ¹H and ¹³C NMR and UV-visible absorption spectra showing that all complexes having analogous geometry and coordination number. The molecular structure of 2 is confirmed by single-crystal X-ray crystallography, which indicates that +2 charges on the metal ion (Ni²⁺) are balanced by dithiocarbamate anion. The X-ray analysis for 2 reveals a distorted square planar geometry around Ni²⁺ ion. Both C?–?H···S and intermolecular C–H···Ni interactions are the only artifact for the resulting Ni-dithiocarbamate architecture in 2. The electrical conductivity measurement between temperatures range of 303–393 K reflects that all complexes exhibit weak semiconducting behavior. Powder XRD, EDAX, and SEM spectra confirm the formation of NiS as thermal decomposition product in 1–3. The crystalline size of samples 1–3 was found to be 20.31?nm, 20.97?nm, and 20.39?nm, respectively.