trans-chelation of the dithioehter, 1,12-bis(phenylthio)-dodecane to planar palladium(II)

The dithioether, 1,12-bis(phenylthio)dodecane (dpd) reacts with tetrachloropalladate(II) and tetrachloroplatinate(II) in ethanol/dichloromethane to form trans-[M(dpd)Cl₂] (M  Pd, Pt); trans-[Pd(dpd)Br₂] has also been isolated. These are the first reported complexes which contain a trans-chelating bidentate ligand involving sulphur donors and is thus further evidence that bulky terminal substituents are not a prerequisite for trans chelation.     

Photophysical Properties and Kinetic Studies of 2-Vinylpyridine-Based Cycloplatinated(II) Complexes Containing Various Phosphine Ligands

A series of cycloplatinated(II) complexes with general formula of [PtMe(Vpy)(PR₃)], Vpy = 2-vinylpyridine and PR₃ = PPh₃ (1a); PPh₂Me (1b); PPhMe₂ (1c), were synthesized and characterized by means of spectroscopic methods. These cycloplatinated(II) complexes were luminescent at room temperature in the yellow–orange region’s structured bands. The PPhMe₂ derivative was the strongest emissive among the complexes, and the complex with PPh₃ was the weakest one. Similar to many luminescent cycloplatinated(II) complexes, the emission was mainly localized on the Vpy cyclometalated ligand as the main chromophoric moiety. The present cycloplatinated(II) complexes were oxidatively reacted with MeI to yield the corresponding cycloplatinated(IV) complexes. The kinetic studies of the reaction point out to an S_N2 mechanism. The complex with PPhMe₂ ligand exhibited the fastest oxidative addition reaction due to the most electron-rich Pt(II) center in its structure, whereas the PPh₃ derivative showed the slowest one. Interestingly, for the PPhMe₂ analog, the trans isomer was stable and could be isolated as both kinetic and thermodynamic product, while the other two underwent trans to cis isomerization.     

Synthesis of a heterodinuclear ruthenium(II)–platinum(II) complex linked by l-cysteine methyl ester

A potential anticancer heterodinuclear ruthenium(II)–platinum(II) complex, [ruthenium(II)(4,4′-dimethyl-2,2′-bipyridine)₂(5-(l-cysteine-methyl ester)-1,10-phenanthroline)-trans-chlorodiammineplatinum(II)] chloride, [Ru(Me₂bipy)₂(5-(l-cysteine-Me)-phen)-trans-Pt(NH₃)₂Cl]Cl₃, was synthesised. l-Cysteine methyl ester was used to link the two metal centres, as more conventional straight chain diaminoalkanes and 2-mercaptoethylamine failed to couple to the phenanthroline ligand. From the precursor mononuclear ruthenium(II) complexes, which were separated into their Δ- and Λ-isomers by column chromatography, the dinuclear complex was synthesised and characterised by ¹H and ¹³C NMR, UV–Vis, circular dichroism, fluorescence and electrospray ionisation mass spectrometry.     

Synthesis and crystal structures of copper(II) and silver(I) complexes of a biphenyl-bridged bipyrazolyl ligand

A semirigid bipyrazolyl ligand, 4,4??-bis[(3??,5??-diethyl-1H-pyrazol-4??-yl)methylene)]-1,1??-biphenyl (H₂L), and four of its Ag(I) and Cu(II) complexes have been prepared and structurally characterized. X-ray analysis demonstrates that the Ag(I) complexes are dinuclear molecular rectangle, while the Cu(II) complexes display a twisted rectangular structure. Two different conformations, namely cis and trans, have been observed for this bipyrazolyl ligand.     

Synthesis and characterization of some trans-hydridomethylbis(phosphine)-platinum(II) and -palladium(II) complexes

Several trans-hydridomethylbis(phosphine)-platinum(II) and -palladium(II) complexes have been made by the reaction: trans-M(H)Cl(PR₃)₂ + CH₃MgBr → trans-M(CH₃)(PR₃)₂ + MgClBr and their structures determined by ¹H NMR and IR spectroscopy. The complexes in which M  Pt and R  Cy (cyclohexyl) or i-Pr (isopropyl) are very stable in the solid state and in solution, while the compounds in which M  Pt, R  Et (ethyl) and M  Pd, R  i-Pr slowly decompose either in the solid state or in solution. The compound in which M  Pd and R  Cy was not isolated but was identified in solution.     

Metal complexes with pyridone-based radicals: Preparation and properties of a dinuclear paddle-wheel copper(II) complex and a mononuclear palladium(II) complex

We prepared and characterized dinuclear copper(II) and mononuclear palladium(II) complexes coordinated with a pyridine-based open-shell ligand, 5-(4′,4′,5′,5′-tetramethylimidazoline-3′-oxide-1′-oxyl)-2(1H)-pyridone (=HL). In the copper(II) dinuclear complex [Cu₂(L)₄(DMF)₂] (1), four deprotonated ligands are coordinated as bridging ligands to form a paddle-wheel type unit. In the palladium(II) complex trans-[PdCl₂(HL)₂] (2), two HL ligands in the neutral hydroxypyridine form are coordinated to the trans positions of the metal ion via the nitrogen atoms. The hydroxyl groups of the ligands are hydrogen-bonded to the chlorine atoms of neighboring molecules, thereby creating a hydrogen-bonded double-chain molecular arrangement. Magnetic susceptibilities of these complexes were measured and analyzed. The small intramolecular antiferromagnetic interaction in the latter complex may originate from superexchange through the diamagnetic metal center.     

Synthesis and properties of nickel(II) and copper(II) complexes of a di-N-acetamide tetraaza macrocycle

The syntheses of the hexadentate ligand 2,13-bis(acetamido)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane (L²) and its complexes with Ni(II) and Cu(II) are described. Crystal structures of H₂L²·2HClO₄ (1), [Ni(L²)](ClO₄)₂ (2) and [Cu(L²)](ClO₄)₂ (3) are reported. The two pendant acetamide groups of the macrocyclic ligand 1 are trans to each other and the absolute configuration is a trans-IV in the solid state. The crystal structures of 2 and 3 revealed an axially elongated octahedral geometry with four nitrogen atoms of the macrocycle and two oxygen atoms of the pendant acetamide groups at the axial positions. The nickel(II) and copper(II) ions are located at an inversion center. The electronic spectra and electrochemical behaviors of the complexes are significantly affected by the presence of the pendant arms.     

Infrared and Raman spectra of ethylene trithiocarbonate complexes of some Zn(II), Cd(II) and Hg(II) halides

Coordination compounds of ethylene trithiocarbonate (ETTC) with some Zn(II), Cd(II) and Hg(II) halides have been prepared, characterized and their infrared and Raman spectra recorded. The i.r. spectra in the range 4000-400 cm⁻¹ suggest that the organic ligand is bonded to the metal ions through its exocyclic sulphur atom, whereas the far-i.r. and Raman spectra show that the complexes of the type HgX₂(ETTC) (X = Cl, Br or I) possess a trans dimeric halogen-bridged structure. The Cd(II) and Zn(II) species are of the type MX₂(ETTC)₂ and they possess a pseudotetrahedral structure of C_2υ symmetry.     

Photochemistry of some alkoxycarbonylplatinum(II) complexes

Alkoxycarbonylplatinum(II) complexes trans-Pt(CO₂CH₂R)Cl(PPh₃)₂, where R = H, Me and Ph, were synthesized in two steps and were characterized by infrared and ultraviolet absorption, proton and phosphorus-31 nuclear magnetic resonance, and mass spectral techniques, and by elemental analysis. Irradiation of the complexes in the solid state or in fluid solution with 254 nm light causes a steady decrease in the intensities of the infrared absorptions in the 1650 and 1070 cm^?1 regions, which is interpreted as signifying labilization of the alkoxycarbonyl ligand. In dichloromethane solution, irradiation causes dissociation of the alkoxycarbonyl ligand, which then decomposes into carbon monoxide and an alkoxide ion. The carbon monoxide is thought to re-coordinate to afford the stable product trans-PtCl(CO)(PPh₃)₂⁺. In the presence of oxygen, triphenylphosphine which dissociates from the metal, is photooxidized to form triphenylphosphine oxide in a parallel photoreaction. Disappearance quantum yields for the alkoxycarbonyl complexes are quite small, Φ ～ 10^?4?10^?3 mol/einstein, and follow the trend H > Me > Ph.     

Mononuclear, trinuclear, and hetero-trinuclear supramolecular complexes containing a new tri-sulfonate ligand and cobalt(II)/copper(II)-(1,10-phenanthroline)2 building blocks

Novel mononuclear, trinuclear, and hetero-trinuclear supermolecular complexes, [Co(phen)₂(H₂O)(HTST)]·2H₂O (1), [Co₃(phen)₆(H₂O)₂(TST)₂]·7H₂O (2), and [Co₂Cu(phen)₆(H₂O)₂(TST)₂]·10H₂O (3), have been synthesized by the reactions of a new tri-sulfonate ligand (2,4,6-tris(4-sulfophenylamino)-1,3,5-triazine, H₃TST) with the M²⁺ (M=Co, Cu) and the second ligand 1,10-phenanthroline (phen). Complex 1 contains a cis-Co(II)(phen)₂ building block and an HTST as monodentate ligand; complex 2 consists of two TST as bidentate ligands connecting one trans- and two cis-Co(II)(phen)₂ building blocks; complex 3 is formed by replacing the trans-Co(II)(phen)₂ in 2 with a trans-Cu(II)(phen)₂, which is the first reported hetero-trinuclear supramolecular complex containing both the Co(II)(phen)₂ and Cu(II)(phen)₂ as building blocks. The study shows the flexible multifunctional self-assembly capability of the H₃TST ligands presenting in these supramolecular complexes through coordinative, H-bonding and even π-π stacking interactions. The photoluminescent optical properties of these complexes are also investigated and discussed as well as the second-order nonlinear optical properties of 1.     

Hydrido Cyanoalkyls of platinum (II)

The preparation and reactions are described of some novel platinum(II) complexes with a hydride ligand group trans to an sp³ carbon, viz. [PtH(YCN)-(PPh₃)₂] with Y  (CH₂)_n (n = 1—3) or o-CH₂C₆H₄.     

A series of hydridoplatinum(II) complexes stabilized with tribenzylphosphines: their preparation,and an empirical approach to the mutual influence of ligands

The preparation, IR and NMR spectra of 123 platinum hydrides of the general formula, trans-PtHX(PBz₃)₂ or trans-PtHL(PBz₃)₂BPh₄ (X = a uninegative anionic ligand, L = a neutral donor molecule, Bz = benzyl), are described. Neutral platinum hydrides have been synthesized by the reduction of trans-PtCl₂-(PBz₃)₂ with NaBH₄, by the Michaelis—Arbuzov rearrangement, or by metathesis. Cationic hydridoplatinum(II) complexes are obtained from the reaction of trans-PtHX(PBz₃)₂ (X = Cl or NO₃) with a donor molecule (L) in the presence of NaBPh₄, or by coordinating a donor molecule through use of PtH(PBz₃)₂BPh₄ · $\text{1}\text{2}$CH₂Cl₂. The observed trends in ν(PtH), τ(H), ¹J(PtH) and ¹J(PtP) in a series of the hydridobenzylphosphineplatinum(II) complexes are discussed in terms of “trans- or cis-influences”, defined as the ability of a ligand to weaken the bond trans or cis to itself. The data support the view that a donor atom trans to the hydridic ligand is important in determining the strength of the PtH bond in this series. Some remarks on the distinctive characteristics of some complexes, e.g., dissociation of coordinated cycloalkanone from platinum(II) or stereochemical non-rigidity of the sym-dimethylurea ligand, are included. Tricyclohexylphosphine analogs also have been prepared for comparison.     

Synthesis,structural, spectroscopic,biological and catalytic activity of Co(II), Ni(II) and Cu(II) complexes of benzilic hydrazide (BH)

Co(II), Ni(II) and Cu(II) chloro complexes of benzilic hydrazide (BH) have been synthesized. Also, reaction of the ligand (BH) with several copper(II) salts, including NO₃ ^?, AcO^?, and SO₄ ^? afforded metal complexes of the general formula [CuLX(H₂O) _n ]·nH₂O, where X is the anion and n = 0, 1 or 2. The newly synthesized complexes were characterized by elemental analysis, mass spectra, molar conductance, UV–vis, IR spectra, magnetic moment, and thermal analysis (TG/DTG). The physico-chemical studies support that the ligand acts as monobasic bidentate towards metal ion through the carbonyl and hydroxyl oxygen atoms. The spectral data revealed that the geometrical structure of the complexes is square planar for Cu (II) complexes and tetrahedral for Co(II) and Ni(II) complexes. Structural parameters of the ligand and its complexes have been calculated. The ligand and its metal complexes are screened for their antimicrobial activity. The catalytic activities of the metal chelates have been studied towards the oxidative decolorization of AB25, IC and AB92 dyes using H₂O₂. The catalytic activity is strongly dependent on the type of the metal ion and the anion of Cu(II) complexes.     

Spectral and structural studies of Ni(II) and Zn(II) complexes of N-trans-cinnamylidene-2-mercaptoaniline

Ni(II) and Zn(II) complexes of the bidentate thiol ligand N-trans-cinnamylidene-2-mercaptoaniline which is obtained from trans-cinnamaldehyde and 2-mercaptoaniline were prepared and characterized by their IR absorption spectra, X-ray powder diffraction measurements, elemental analysis and ¹H-NMR spectra. On the other hand, energy minimization studies of the molecules were carried out to obtain the most probable three-dimensional molecular conformations.The comparative ¹H-NMR, IR, X-ray powder diffraction and energy minimization studies have shown that metal atoms are connected to the N and S atoms of Schiff bases and the complex have cis type fashion.     

Copper(II)-saccharinato complexes with piperazine and N-(2-aminoethyl)piperazine ligands

Two copper(II) complexes of the saccharinate anion (sac) with piperazine (ppz) and N-(2-aminoethyl)piperazine (aeppz), namely [Cu(sac)₂(ppz)(H₂O)]_n (1) and trans-[Cu(sac)₂(aeppz)₂] (2), have been synthesized and characterized by elemental analyses, UV–Vis, FT-IR, TGA/DTA, X-ray diffraction and magnetic measurements. The ppz ligands in 1 bridge the copper(II) centers through both nitrogen atoms to form a 1D helical chain structure and the distorted trigonal-bipyramidal coordination geometry at each copper center is completed by an aqua and a pair of N-bonded sac ligands. The helical chains are linked by Ow–H?O hydrogen bonds to build a 2-D network. In complex 2, copper(II) ions are octahedrally coordinated by two sac anions and two neutral aeppz ligands, displaying a distorted octahedral coordination. Sac is O-bonded via the carbonyl group, while ppzea acts as a N,N′-bidentate chelating ligand. The molecules are connected by N–H?N and N–H?O hydrogen bonds, forming a linear chain. In the thermal decomposition of both complexes, the removal of the aqua and ppz or aeppz ligand takes place endothermically in the first stages and the sac moiety undergoes highly exothermic decomposition at higher temperatures to give CuO.     

Synthesis,characterization and biological studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes with pyrral-l-histidinate

The Schiff base ligand, pyrral-l-histidinate(L) and its Co(II), Ni(II), Cu(II) and Zn(II) complexes were synthesized and characterized by elemental analysis, mass, molar conductance, IR, electronic, magnetic measurements, EPR, redox properties, thermal studies, XRD and SEM. Conductance measurements indicate that the above complexes are 1:1 electrolytes. IR data show that the ligand is tridentate and the binding sites are azomethine nitrogen, imidazole nitrogen and carboxylato oxygen atoms. Electronic spectral and magnetic measurements indicate tetrahedral geometry for Co(II) and octahedral geometry for Ni(II) and Cu(II) complexes, respectively. The observed anisotropic g values indicate the presence of Cu(II) in a tetragonally distorted octahedral environment. The redox properties of the ligand and its complexes have been investigated by cyclic voltammetry. Thermal decomposition profiles are consistent with the proposed formulations. The powder XRD and SEM studies show that all the complexes are nanocrystalline. The in vitro biological screening effects of the synthesized compounds were tested against the bacterial species, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus; fungal species, Aspergillus niger, Aspergillus flavus and Candida albicans by the disc diffusion method. The results indicate that complexes exhibit more activity than the ligand. The nuclease activity of the ligand and its complexes were assayed on CT DNA using gel electrophoresis in the presence and absence of H₂O₂.     

Identification of Pt(II) and Pd(II) stereoisomeric complexes with aminobutyric acid by NMR and IR spectroscopy

Complexes of Pd(II) with aminobutyric acid AmH = NH₂CH(CH₂CH₃)COOH, namely, trans-[Pd(AmH)₂Cl₂] with monodentate (via the NH₂ group) AmH ligands and cis-, trans-Pd(Am)₂ with bidentate (via NH₂ and COO groups) ligands have been synthesized for the first time. Elemental analysis and IR and NMR spectroscopy were used to identify the synthesized compounds. The NMR spectra of the Pd(II) complexes were interpreted by comparing them with the NMR spectra of the analogous complexes of Pt(II). For Pt(II) and Pd(II) complexes with aminobutyric acid used as examples, an approach to identification of diastereomer bis-aminoacid complexes in specimens with racemic aminoacids by NMR spectroscopy is demonstrated.     

Ab-initio Calculations of T-shaped Phosphine-Platinum(II) Complexes

 The geometries and total energies of several T-shaped platinum(II) complexes of the type (H₃P)PtXY (X, Y=Cl, CH₃, SiH₃, Si(OH)₃) were calculated by ab-initio methods. In the most stable isomer, the ligand with the smallest trans influence is trans to the PH₃ ligand. The trans influence increases in the order Cl<CH₃<SiH₃<Si(OH)₃.     

Synthesis and spectral characterization of zinc(II) and cadmium(II) complexes of acetone-N(4)-phenylsemicarbazone: Crystal structures of acetone-N(4)-phenylsemicarbazone and a cadmium(II) complex

Seven Zn(II) and Cd(II) complexes of ON donor acetone-N(4)-phenylsemicarbazone (HL) have been synthesized and physico-chemically characterized by partial elemental analyses, molar conductance measurements, infrared, electronic and ¹H NMR spectral studies. The semicarbazone binds the metal as a neutral bidentate ligand in all the complexes. The crystal structures of acetone-N(4)-phenylsemicarbazone and [Cd(HL)₂Cl₂] have been determined by X-ray diffraction studies. The coordination geometry around cadmium(II) in the complex [Cd(HL)₂Cl₂] is distorted octahedral.     

Synthesis and structure of highly substituted pyrazole ligands and their complexes with platinum(II) and palladium(II) metal ions

Reaction of 3-methoxycarbonyl-2-methyl- or 3-dimethoxyphosphoryl-2-methyl-substituted 4-oxo-4H-chromones 1 with N-methylhydrazine resulted in the formation of isomeric, highly substituted pyrazoles 4 (major products) and 5 (minor products). Intramolecular transesterification of 4 and 5 under basic conditions led, respectively, to tricyclic derivatives 7 and 8. The structures of pyrazoles 4a (dimethyl 2-methyl-4-oxo-4H-chromen-3-yl-phosphonate) and 4b (methyl 4-oxo-2-methyl-4H-chromene-3-carboxylate) were confirmed by X-ray crystallography. Pyrazoles 4a and 4b were used as ligands (L) in the formation of ML₂Cl₂ complexes with platinum(II) or palladium(II) metal ions (M). Potassium tetrachloroplatinate(II), used as the metal ion reagent, gave both trans-[Pt(4a)₂Cl₂] and cis-[Pt(4a)₂Cl₂], complexes with ligand 4a, and only cis-[Pt(4b)₂Cl₂] isomer with ligand 4b. Palladium complexes were obtained by the reaction of bis(benzonitrile)dichloropalladium(II) with the test ligands. trans-[Pd(4a)₂Cl₂] and trans-[Pd(4b)₂Cl₂] were the exclusive products of these reactions. The structures of all the complexes were confirmed by IR, ¹H NMR and FAB MS spectral analysis, elemental analysis and Kurnakov tests.