Square Planar Structure Research Articles

A novel square-planar Ni(II) complex with an amino-carboxamido-dithiolato-type ligand as an active-site model of NiSOD.

To understand the role of the unique equatorial coordination environment at the active center in nickel superoxide dismutase (NiSOD), we prepared a novel Ni(II) complex with an amino-carboxamido-dithiolato-type square-planar ligand (1, [Ni(2+)(L1)](-)) as a model of the NiSOD active site. Complex 1 has a low-spin square-planar structure in all solvents. Interestingly, the absorption wavelength and ν(C═O) stretching vibrations of 1 are affected by solvents. This provides an indication that the carbonyl oxygens participate in hydrogen-bonding interactions with solvents. These interactions are reflected in the redox potentials; the peak potential of an anodic wave (Epa) values of Ni(II)/Ni(III) waves for 1 are shifted to a positive region for solvents with higher acceptor numbers. This indicates that the disproportionation of superoxide anion by NiSOD may be regulated by hydrogen-bonding interactions between the carboxamido carbonyl and electrophilic molecules through fine-tuning of the redox potential for optimal SOD activity. Interestingly, the Epa value of the Ni(III)/Ni(II) couple in 1 in water (+0.303 V vs normal hydrogen electrode (NHE)) is similar to that of NiSOD (+0.290 V vs NHE). We also investigated the superoxide-reducing and -oxidizing reactions of 1. First, 1 reacts with superoxide to yield the superoxide-bound Ni(II) species (UV-vis: 425, 525, and ∼650 nm; electron paramagnetic resonance (EPR) (4 K): g// = 2.21, g⊥ = 2.01; resonance Raman: ν((16)O-(16)O)/ν((18)O-(18)O) = 1020/986 cm(-1)), which is then oxidized to Ni(III) state only in the presence of both a proton and 1-methylimidazole, as evidenced by EPR spectra. Second, EPR spectra indicate that the oxidized complex of 1 with 1-methylimidazole at the axial site can be reduced by reaction with superoxide. The Ni(III) complex with 1-methylimidazole at the axial site does not participate in any direct interaction with azide anion (pKa 4.65) added as mimic of superoxide (pKa 4.88). According to these data, we propose the superoxide disproportionation mechanism in superoxide-reducing and -oxidizing steps of NiSOD in both Ni(II) and Ni(III) states.

Syntheses and characterization of palladium(II) complexes with a bidentate bis-NHC ligand having methyl and aryl substituents on terminal nitrogen atoms

An imidazolium salt, N-chloromethyl-N′-methylimidazolium bromide was prepared as an intermediate for the syntheses of unsymmetrical bidentate bis-NHC ligands bearing methyl and aryl substituents on the terminal nitrogen atoms. Three bis-NHC ligand precursors and their corresponding palladium(II) complexes were also prepared. 1H NMR spectra of the imidazolium salts of the bidentate ligands implied that the carbene on a methyl-substituted imidazolylidene ring is a stronger donor than one on an aryl-substituted ring. The crystal structures of the palladium(II) complexes showed a distorted square-planar structure. The complexes demonstrated good catalytic performance in the Heck reaction.

Coordination of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), Pd(II) and Pt(II) with 2,5-hexanedione bis(thiosemicarbazone), HBTS: Crystal structure of cis-[Pd(HBTS)]Cl2 and 1-(2,5-dimethyl-1H-pyrrol-yl)-thiourea

Metal complexes of Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pd2+ or Pt2+ with 2,5-hexanedione bis(thiosemicarbazone), HBTS; have been prepared and spectroscopically investigated. The empirical formulae of the complexes were suggested based on the elemental analysis. Single crystal of Pd(II) has been solved to be cis-form of square-planar geometry by the X-ray crystallography. 1H and 13C NMR spectra have been recorded for HBTS, Zn(II), Cd(II), Hg(II), Pd(II) and Pt(II) complexes, in DMSO-d6, showing the mode of chelation. The ligand acts as a neutral or a binegative tetradentate (N2S2) or neutral bidentate on the basis of FT-IR. The magnetic moments and electronic spectra provide information about the geometry of the complexes which supported by calculating the ligand field parameters for the Co(II) and Fe(III) complexes. The Ni(II) complex has subnormal magnetic moment (0.71BM) indicative of a mixed stereochemistry of square-planar and tetrahedral structure. [Cu(HBTS-2H)] measured 0.93BM indicating high interaction between the copper centers. The ligand may be ordered at the top of the spectrochemical series which giving high ligand field splitting energy (10Dq=17,900cm−1 for Co2+ complex). The mass spectra of some complexes proved their stable chemical formulae while the TGA depicts the degradation steps and the final residue. In evaporating the mother liquor during the preparation of HBTS, new compound is obtained naming 1-(2,5-dimethyl-1H-pyrrol-yl)thiourea and its crystal was solved.

On the cytotoxic activity of Pd(II) complexes of N,N-disubstituted-N′-acyl thioureas

The rational design of anticancer drugs is one of the most promising strategies for increasing their cytotoxicity and for minimizing their toxicity. Manipulation of the structure of ligands or of complexes represents a strategy for which is possible to modify the potential mechanism of their action against the cancer cells. Here we present the cytotoxicity of some new palladium complexes and our intention is to show the importance of non-coordinated atoms of the ligands in the cytotoxicity of the complexes. New complexes of palladium (II), with general formulae [Pd(PPh3)2(L)]PF6 or [PdCl(PPh3)(L)], where L=N,N-disubstituted-N′-acyl thioureas, were synthesized and characterized by elemental analysis, molar conductivity, melting points, IR, NMR(1H, 13C and 31P{1H}) spectroscopy. The spectroscopic data are consistent with the complexes containing an O, S chelated ligand. The structures of complexes with N,N-dimethyl-N′-benzoylthiourea, N,N-diphenyl-N′-benzoylthiourea, N,N-diethyl-N′-furoylthiourea, and N,N-diphenyl-N′-furoylthiourea were determined by X-ray crystallography, confirming the coordination of the ligands with the metal through sulfur and oxygen atoms, forming distorted square-planar structures. The N,N-disubstituted-N′-acyl thioureas and their complexes were screened with respect to their antitumor cytotoxicity against DU-145 (human prostate cancer cells), MDA-MB-231 (human breast cancer cells) and their toxicity against the L929 cell line (health cell line from mouse).

Structure and spectroscopic studies of homo-and heterometallic complexes of adipic acid dihydrazide

A single crystal of adipic acid dihydrazide, ADH, has been analyzed. Its reaction with Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Ag+, Pd2+ and/or Pt2+ gave homometallic and heterometallic complexes which are characterized by partial elemental analysis, spectra (MS, ESR, 1H NMR, electronic; IR), thermal analysis and magnetic measurements. Some complexes: Zn0.73Cu(ADH)Cl4·H2O; Zn0.71Hg0.36(ADH)Cl4·H2O; Zn0.65Cd0.46(ADH)Cl4·½H2O; Zn0.75Co0.41(ADH-2H)Cl2·3H2O; Cd0.85Co0.43(ADH)Cl4·½EtOH were isolated having nonstiochiometric metal ratios. The ligand behaves as a neutral (bidentate or tetradentate) and/or binegative tetradentate. A square-pyramid, square-planar and tetrahedral structures were proposed for the homo Co(II), Cu(II) and Ni(II) complexes, respectively. A similar and different stereochemistry around each metal ion (tetrahedral+tetrahedral; tetrahedral+square-planar; tetrahedral+tetrahedral and/or tetrahedral+octahedral) was suggested for the heterometallic complexes. Some complexes were found highly stable with stability point >240°C; the most stable is [HgNi(ADH-2H)Cl2]. The presence of diamagnetic atom (Zn, Cd or Hg) reduces the magnetic moments and gave anomalous moments. The degradation steps and the hydrated complexes are confirmed through the TGA study. The order of covalency of [Zn0.73Cu(ADH)Cl4]·H2O, [CdCu(ADH)Cl4]·H2O and [HgCu(ADH-2H)Cl2] matches with the size of the second metal (Zn complex>Cd complex>Hg complex). Some heterometallic complexes were found nonstoichiometric through the analysis of their metal content and supported by TGA.

A stable, mononuclear, cationic Pt(iii) complex stabilised by bulky N-heterocyclic carbenes

The thermally stable, paramagnetic Pt(iii) complex [PtI2(IPr)2][BAr(F)] has been prepared by oxidation of the Pt(ii) complex [PtI2(IPr)2] with iodine in the presence of NaBAr(F). X-ray crystallographic studies revealed the mononuclear nature of this species with a square-planar geometry. EPR and DFT studies pointed out to a metal-centred radical.

Physicochemical, Spectral, and Biological Studies of Mn(II), Cu(II), Cd(II), Zr(OH)2(IV), and UO2(VI) Compounds with Ligand Containing Thiazolidin-4-one Moiety

The Schiff base (I) upon reacting with mercaptoacetic acid in dry benzene undergoes cyclization and forms N-(2-carbamoylthienyl)-C-(3′-carboxy-2′-hydroxyphenyl)thiazolidin-4-one, LH3(II). A MeOH solution ofIIreacts with Mn(II), Cu(II), Cd(II), Zr(OH)2(IV), and UO2(VI) ions and forms the coordination compounds, [Mn(LH)(MeOH)2], [Cu(LH)]2, [Cd(LH)], [Zr(OH)2(OAc)2(LH3)], and [UO2(NO3)(LH2)(MeOH)]. The compounds have been characterized on the basis of elemental analyses, molar conductance, molecular weight, spectral (IR, reflectance, and EPR) studies and magnetic susceptibility measurements. LH3behaves as a neutral tridentate ONS donor ligand in [Zr(OH)2(OAc)2(LH3)], monobasic tridentate ONS donor ligand in [UO2(NO3)(LH2)(MeOH)], dibasic tridentate OOS donor ligand in [Cu(LH)]2and dibasic tetradentate OONO donor ligand in [Mn(LH)(MeOH)2] and [Cd(LH)]. [Cu(LH)]2is dimer, while all other compounds are monomers in diphenyl. A square-planar structure for [Cu(LH)]2, a tetrahedral structure for [Cd(LH)], an octahedral structure for [Mn(LH)(MeOH)2], a pentagonal-bipyramidal structure for [Zr(OH)2(OAc)2(LH3)], and an eight-coordinate structure for [UO2(NO3)(LH2)(MeOH)] are proposed. The ligand (II) and its compounds show antibacterial activities towardsE. coli. (Gram negative) andS. aureus(Gram positive).

Synthesis, structure and biological activities of Pd(II) and Pt(II) complexes with 2-(diphenylphosphino)benzaldehyde 1-adamantoylhydrazone

The reaction of an ethanolic solution of the newly synthesized 2-(diphenylphosphino)benzaldehyde 1-adamantoylhydrazone (HL) with aqueous solutions of K2[MCl4] (M=Pd(II), Pt(II)) resulted in neutral complexes of the general formulae [M(L)Cl]. These complexes have a square-planar structure that was achieved by tridentate PNO coordination of the monoprotonated Schiff base and a chloride ligand. The ligand and its metal complexes were analyzed for their antimicrobial activity and their in vitro cytotoxicity in human larynx carcinoma cells (Hep-2) and non-cancerous human lung fibroblast cells (MRC-5). The platinum(II) complex shows cytotoxicity towards Hep-2 cells comparable to oxaliplatin and exhibited improved selectivity for cancer cells. The ligand and its complexes were characterized by elemental analysis, NMR and IR spectroscopy, and single crystal X-ray diffraction analysis.

Homogeneous Hydrogenation and Isomerization of 1-Octene Catalyzed by Nickel(II) Complexes with Bidentate Diarylphosphane Ligands

A systematic library of 24 nickel(II) complexes with bidentate diphosphane ligands was synthesized, and the solid-state structures of five of them were determined with X-ray crystallography. The compounds C1-C3 are common P2Ni(II)X2-type complexes, while C4 contains a unique [P2Ni(II)(NH3)(OAc)](+) square-planar structure with a P2NO donor set and C5 constitutes a rare [(P2Ni(II))2(μ-OH)2](2+) dinuclear compound. The catalytic activity of all complexes was tested in the hydrogenation and/or isomerization of 1-octene in a CH2Cl2/CH3OH reaction medium. Catalyst precursors bearing ligands with o-alkoxy aryl rings selectively hydrogentate 1-octene to n-octane, while catalytic systems comprising ligands without the o-alkoxy functionality selectively isomerize the substrate to a mixture of internal alkenes, mostly cis- and trans-2-octene. The conversion is enhanced by equipping the ligand aryl rings with electron-donating alkoxy groups, by increasing the steric bulk of the backbone and/or the aryl rings, by employing relatively noncoordinating anions, and by adding a base as the cocatalyst. Using the compound [Ni(L3X)I2] as the catalyst precursor and upon application of standard hydrogenation conditions, full conversion of the substrate was achieved in 1 h to isomerization products only (TON = 1940). When a catalytic amount of the base is added, a similar result is obtained even in the absence of H2. A maximum TON of 4500 in 1 h with 96% selectivity for n-octane was achieved by employing [Ni(oMeO-L3X)(NH3)(OAc)]PF6 as the catalyst precursor.

Synthesis, characterization, and electrochemical study of some novel, azo-containing Schiff bases and their Ni(II) complexes

Abstract Five novel azo-azomethine ligands with NN'OS coordination spheres were prepared by reaction of methyl-2-{ N -(2′-aminoethane)}-amino-1-cyclopentenedithiocarboxylate (Hcden) with ( E )-2-hydroxy-5-(phenyldiazenyl)benzaldehyde and its substituted derivatives and then the corresponding nickel(II) complexes were synthesized. The structures of ligands and the complexes were characterized by elemental analyses, IR, UV–Vis, 1 H NMR spectroscopy and cyclic voltammetry. The structures of (methyl 2-(2-(( E )-2-hydroxy-5-(( E )- p -tolyldiazenyl)benzyli deneamino)ethylamino)cyclopent-1-enecarbodithioato)nickel(II) and (methyl 2-(2-(( E )-5-(( E )-(4-chlorophenyl)diazenyl)-2-hydroxybenzylideneamino)ethylamino)cyclopent-1-enecarbodithioato)-nickel(II) have been determined by X-ray crystallography. The X-ray results confirm that the geometry of the complexes are slightly distorted square-planar structures. The nickel(II) ions coordinate to two nitrogen atoms from the imine moiety of the ligand, a sulfur atom from the methyl dithiocarboxylate moiety and a phenolic oxygen atom.

Synthesis and Characterization of New Platinum(II) and Platinum(IV) Triphyrin Complexes

Metalation of 6,13,20,21-tetrakis(4-methylphenyl)-22H-tribenzo[14]triphyrin(2.1.1) with PtCl(2) gave a platinum(II) complex having a square-planar coordination structure with two pyrrolic nitrogen atoms and two chloride ions, with a saddle-shaped macrocycle. This platinum(II) complex was easily oxidized by air to an octahedral platinum(IV) complex coordinated by three pyrrolic nitrogen atoms as a tridentate monoanionic cyclic ligand and three chloride ions. When platinum(II) triphyrin was crystallized in air, an oxygen atom was incorporated between two α-carbon atoms of the pyrroles as an oxygen bridge to intercept the 14π aromatic system.

Syntheses, Spectral Characterization, and Antimicrobial Studies on the Coordination Compounds of Metal Ions with Schiff Base Containing Both Aliphatic and Aromatic Hydrazide Moieties

An EtOH solution of 3-ketobutanehydrazide and salicylhydrazide on refluxing in equimolar ratio forms the corresponding Schiff base, LH3 (1). The latter reacts with Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Zr(OH)2(IV), MoO2(VI), and UO2(VI) ions in equimolar ratio and forms the corresponding coordination compounds, [M(LH)(MeOH)3] (2, M = Mn, Co, Ni), [Cu(LH)]2 (3), [M′(LH)(MeOH)] (4, M′ = Zn, Cd), [Zr(OH)2(LH)(MeOH)2] (5), [MoO2(LH)(MeOH)] (6), and [UO2(LH)(MeOH)] (7). The coordination compounds have been characterized on the basis of elemental analyses, molar conductance, spectral (IR, reflectance, 1H NMR, ESR) studies, and magnetic susceptibility measurements. They are nonelectrolytes in DMSO. The coordination compounds, except 3, are monomers in diphenyl. They are active against gram-positive bacteria (S. aureus, B. subtilis), gram-negative bacteria (E. coli, P. aeruginosa), and yeast (S. cerevisiae, C. albicans). 1 acts as a dibasic tridentate ONO donor ligand in 2–7 coordinating through its both enolic O and azomethine N atoms. The coordination compounds 2 and 3 are paramagnetic, while rest of the compounds are diamagnetic. A square-planar structure to 3, a tetrahedral structure to 4, an octahedral structure to 2, 6, and 7, and a pentagonal bipyramidal structure to 5 are proposed.

Highly emissive platinum(ii) complexes bearing carbene and cyclometalated ligands

A series of heteroleptic platinum(II) complexes (1a-3a and 1b-3b) bearing a dicarbene ligand and a cyclometalated bidentate ligand have been prepared. Two of the complexes (1a and 3a) were characterized by X-ray diffraction analyses, confirming the square-planar structures. Detailed spectroscopic properties of the complexes have been studied, and two complexes, 3a and 3b bearing a carbene chelate, which has a trimethylene group between the two N-heterocyclic carbene ligating groups, show intense luminescence (quantum yields >50%) in fluid solution at room temperature. Non-radiative rate constants of the emissive excited states of the complexes vary markedly among the 6 complexes, although radiative constants of them lie in a narrow range of values, so that the difference in the photophysical properties is ascribed to the difference in the non-radiative decay rates. The photophysical parameters have been discussed with the results of the quantum mechanical calculations. The DFT and TDDFT calculations show that the emissive excited states have mainly ligand-centered character with a slight contribution of MLCT.

Synthesis, Characterization and Biological Activities of 4-(p-Chlorophenyl)-1-(pyridin-2-yl)thiosemicarbazide and Its Metal Complexes

New series of metal complexes of Co(II), Ni(II), Cu(II), Zn(II), Pd(II) and Pt(II) with 4-(p-chlorophenyl)-1-(pyridin-2-yl)thiosemicarbazide (HCPTS) have been synthesized and characterized by elemental analyses, magnetic moment, spectra (IR, UV-Vis, <TEX>$^1H$</TEX> NMR, mass and ESR) and thermal studies. The IR data suggest different coordination modes for HCPTS which behaves as a monobasic bidentate with all metal ions except Cu(II) and Zn(II) which acts as a monobasic tridentate. Based on the electronic and magnetic studies, Co(II), Cu(II), Pd(II) and Pt(II) complexes have square - planner, Ni(II) has mixed stereochemistry (tetrahedral + square planar), while Zn(II) is tetrahedral. Molar conductance in DMF solution indicates the non-ionic nature of the complexes. The ESR spectra of solid copper(II) complex show <TEX>$g_{\parallel}$</TEX> (2.2221) > <TEX>$g_{\perp}$</TEX> (2.0899) > 2.0023 indicating square-planar structure and the presence of the unpaired electron in the <TEX>$d_x2_{-y}2$</TEX> orbital with significant covalent bond character. The thermal stability and degradation kinetics of the ligand and its metal complexes were studied by TGA and DTA and the kinetic parameters were calculated using Coats-Redfern and Horowitz-Metzger methods. The complexes have more antibacterial activity against some bacteria than the free ligand. However, the ligand has high anticancer activities against HCT116 (human colon carcinoma cell line) and HEPG2 (human liver hepatocellular carcinoma cell line) compared with its complexes.

{2,6-Bis[(2,6-diisopropylphosphanyl)oxy]-4-fluorophenyl-κ3P,C1,P′}(1H-pyrazole-κN2)nickel(II) hexafluorophosphate

The title compound, [Ni(C18H30FO2P2)(C3H4N2)]PF6, was prepared by halide abstraction with TlPF6 in the presence of CH3CN in CDCl3 from the respective neutral pincer chlorido analogue followed by addition of pyrazole. The PO—C—OP pincer ligand acts in typical trans-P2 tridentate fashion to generate a distorted square-planar nickel structure. The Ni—N(pyrazole) distance is 1.925 (2) Å and the plane of the pyrazole ligand is rotated 56.2 (1)° relative to the approximate square plane surrounding the NiII center in which the pyrazole is bound to the NiII atom through its sp 2-hybridized N atom. This Ni—N distance is similar to bond lengths in the other reported NiII pincer-ligand square-planar pyrazole complex structures; however, its dihedral angle is significantly larger than any of those for the latter set of pyrazole complexes.

Mixed-ligand nickel(II) and copper(II) complexes of tridentate ONS and NNS ligands derived from S-alkyldithiocarbazates with the saccharinate ion as a co-ligand

New mixed-ligand complexes of the general formula, [M(L)(sac)] (M=Ni2+, Cu2+; L−=anionic forms of the salicylaldehyde Schiff base of N-methyl-S-methyldithiocarbazate (Hsalsme), the salicylaldehyde 2-N-methyl-3-thiosemicarbazone (Hsaltsc), the methylpyruvate Schiff base of S-methyldithiocarbazate (Hmpsme) and the quinoline-2-methoxycarboxaldehyde Schiff base of S-methyldithiocarbazate (quinolsme); sac−=the saccharinate anion) have been synthesized and characterized by IR, electronic and magnetic susceptibility measurements. Magnetic and spectroscopic data support a distorted square-planar structure for the [M(ONS/NNS)(sac)] complexes (ONS/NNS=salsme, saltsc, mpsme or quinolsme).The structures of Hsalsme, [Cu(salsme)sac] and [Cu(quinolsme)sac] have been determined by X-ray diffraction. The complex, [Cu(salsme)sac] has a distorted square-planar structure with the Schiff base acting as a uninegatively charged ONS tridentate chelating agent coordinating the copper(II) ion via the phenolic oxygen, the azomethine nitrogen and the thione sulfur atoms, the fourth coordination position being occupied by an N-bonded saccharinate anion.The reaction of [Cu(sac)4(H2O)2]·2H2O with the 2-quinolinecarboxaldehyde Schiff base of S-methyldithiocarbazate (Hqsme) in boiling methanol does not lead to the formation of the expected mixed-ligand complex, [Cu(qsme)(sac)], but an unusual substitution of the hydrogen atom attached to the azomethine carbon by a methoxy group occurs with the concomitant formation of the complex [Cu(quinolsme)(sac)] of a new ligand (quinolsme=anionic form of the quinolone-2-methoxycarboxaldehyde Schiff base of S-methyldithiocarbazate). An X-ray crystal structure determination reveals that the Schiff base Hquinolsme is coordinated to the copper(II) ion in its deprotonated thiolate form as an NNS tridentate chelating agent and the fourth coordination position of the square-planar copper(II) centre is occupied by an N-bonded saccharinate anion.

Synthesis, characterization and electrochemical study of synthesis of a new Schiff base (H2cdditbutsalen) ligand and their two asymmetric Schiff base complexes of Ni(II) and Cu(II) with NN′OS coordination spheres

A novel Schiff base (H2cdditbutsalen) ligand was prepared via condensation of Methyl-2-{N-(2′-aminoethane)}-amino-1-cyclopentenedithiocarboxylate(Hcden) and 3,5-di-tert-butyl-2-hydroxybenzaldehyde. The ligand and Ni(II) and Cu(II) complexes were characterized based on elemental analysis, IR, 1H NMR, 13C NMR, UV–Vis spectrometry and cyclic voltammetry. The structure of copper{methyl-2-{N-[2-(3,5-di-tert-butyl-2-hydroxyphenyl)methylidynenitrilo]ethyl}amino-1-cyclopentedithiocarboxylate has been determined by X-ray crystallography. The X-ray results confirm that the geometry of the complex is slightly distorted square-planar structure. The copper(II) ion coordinates to two nitrogen atoms from the imine moiety of the ligand, a sulfur atom the methyl dithiocarboxylate moiety and phenolic oxygen atom.

Molecular and Crystal Structure of Potassium-L-alaninatodichloridoplatinate( II), K[Pt(L-alaO)Cl2

The square-planar structure of the [Cl2Pt(alaninate)]- anion was determined by X-ray crystallography. In the crystal structure the packing of the components is dominated by layers of potassium ions

Synthesis, structural characterization and electrochemical studies of nickel(II), copper(II) and cobalt(III) complexes of some ONS donor ligands derived from thiosemicarbazide and S-alkyl/aryl dithiocarbazates

Four tridentate ONS ligands, namely 2-hydroxyacetophenonethiosemicarbazone (H2L1), the 2-hydroxyacetophenone Schiff base of S-methyldithiocarbazate (H2L2), the 2-hydroxy-5-nitrobenzaldehyde Schiff base of S-methyldithiocarbazate (H2L3), and the 2-hydroxy-5-nitrobenzaldehyde Schiff base of S-benzyldithiocarbazate (H2L4), and their complexes of general formula [Ni(HL1)2], [ML] (M = NiII or CuII; L = L1, L2, L3 and L4), [Co(HL)(L); L = L1, L2, L3 and L4] and [ML(B)] (M = NiII or CuII; L = L2 and L4; B = py, PPh3) have been prepared and characterized by physico-chemical techniques. Spectroscopic evidence indicates that the Schiff bases behave as ONS tridentate chelating agents. X-ray crystallographic structure determination of [NiL2(PPh3)] and [CuL4(py)] indicates that these complexes have an approximately square-planar structure with the Schiff bases acting as dinegatively charged ONS tridentate ligands coordinating via the phenoxide oxygen, azomethine nitrogen and thiolate sulfur atoms. The electrochemical properties of the complexes have been studied by cyclic voltammetry.

Bis(μ-diisopropylphosphanido-κ2 P:P)bis[hydrido(triisopropylphosphane-κP)platinum(II)

In the centrosymmetric mol­ecular structure of the title compound [Pt2(C6H14P)2H2(C9H21P)2], each PtII atom is bound on one side to a phosphane ligand (PiPr3) and a hydrido ligand. On the other side, it is bound to two phosphanide ligands (μ-PiPr2), which engage a bridging position between the two PtII atoms, forming a distorted square-planar structure motif. The Pt⋯Pt distance is 3.6755 (2) Å. A comparable mol­ecular structure was observed for bis­(μ-di-tert-butyl­phosphanido)bis­[hydrido(triethyl­phosphane)platinum(II)] [Itazaki et al. (2004 ▶). Organometallics, 23, 1610–1621].