Addition of protic molecules to coordinated 2-pyridinecarboxaldehyde in gold(III), palladium(II), and platinum(II) complexes

The reactions of Au^III, Pt^II and Pd^II complexes with 2-pyridinecarboxaldehyde (2CHO-py) have been examined in protic (H₂O, MeOH, EtOH) and aprotic (DMF, CH₂Cl₂) solvents. Compounds in which the pyridine ligand is N-coordinated, either in the original aldehydic form or in a new form derived from addition of one or two protic molecules, have been isolated, namely: [Au(2CHO-py · H₂O)Cl₃], [Au(2CHO-py · MeOH)Cl₃], [Au(2CHO-py · 2EtOH)Cl₃], cis-[Pt(2CHO-py)₂Cl₂], trans-[Pd(2CHO-py)₂Cl₂], trans-[Pt(dmso)(2CHO-py)Cl₂], [Pt{C₅H₄N-(CH₂SMe)}Cl(2CHO-py)](ClO₄), [Pt(terpy)(2CHOpy)](ClO₄)₂, [Pt(terpy)(2CHO-py · H₂O)](ClO₄)₂ (terpy = 2,2′:6′,2′′-terpyridine). ¹H-n.m.r. experiments show that the addition of the protic molecule(s) to the Pt^II and Pd^II complexes is reversible. The effects of the nature of the metal ion and the ancillary ligands as well as of the total charge of the complexes on the relative stability of the addition products are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Thermal and structural properties of coordination compounds of 2-mercapto-1-methylimidazole with palladium(II) and platinum(II)

Complexes of 2-mercapto-1-methylimidazole (TMZ) with Pd^II and Pt^II of the general formula M(TMZ)_nX₂ (whereM=Pd, Pt andX=Cl, Br, I or SO₄ andn=2 or 4) were obtained. The thermal stabilities of the compounds were estimated by derivatographic measurements and lattice constants were estimated from their X-ray powder diffraction patterns.     

Complexes of 1-isonicotinoyl-4-benzoyl-3-thiosemicarbazide with manganese(II), iron(III), chromium(III), cobalt(II), nickel(II), copper(II) and zinc(II)

1-Isonicotinoyl-4-benzoyl-3-thiosemicarbazide (IBtsc) and its Cr^III, Mn^II, Fe^III, Co^II, Ni^II, Cu^II and Zn^II complexes have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, u.v.–vis., i.r., n.m.r. and FAB mass spectral data. The room temperature e.s.r. spectra of the Cr^III, Fe^III and Cu^II complexes yield values, characteristic of octahedral, tetrahedral and square-planar complexes, respectively. The Mössbauer spectra of [Fe(IBtsc-H)Cl₂] at room temperature and at 78 K suggest the presence of high-spin Fe^III. The Ni^II, Cr^III and Cu^II complexes show semiconducting behaviour in the solid state, but the Zn^II complex is an insulator at room temperature. IBtsc and its soluble complexes have been screened against several bacteria, fungi and tumour cell lines.     

Axial-ligation and macrocyclization of novel (E,E)-dioximes of nickel(II) palladium(II), platinum(II) and cobalt(III)

Summary The synthesis and characterization of new Ni^II, Pd^II, Pt^II and Co^III complexes, with the BF _inf2 ^sup+ -bridged,bis(-di-oximato) ligands are described. The initially formed six-coordinate hydrogen-bonded macrocycles, were used as metal templates to prepare the corresponding BF _inf2 ^sup+ - capped macrocycles. The complexes were characterized by¹H-n.m.r. and i.r. spectroscopy, and by elemental analysis.     

Solvolysis of palladium(II) and platinum(II) complexes of asymmetric ligands: Synthesis and structural characterization of [Pd(AMP)(dmso)Cl]BF4 and [Pt(AMP)(dmso)Cl]ClO4

Treatment of [M(AMP)Cl₂] (M = Pt^II, Pd^II; AMP = 2-aminomethylpyridine) with 1 mole of AgX (X = ClO₄, BF₄, PF₆) in dmso yields [M(AMP)(dmso)Cl]X. Single crystal X-ray structure determinations of the Pd^II and Pt^II complexes indicate that dmso is S-bondedtrans to the pyridyl ring in both complexes. (2-Aminomethylpyridine)chloro(dimethylsulphoxide-S) palladium(II) tetrafluoroborate.     

Chromium(III), manganese(II), cobalt(II), nickel(II), copper(II) and palladium(II) complexes of a 12-membered tetraaza [N4] macrocyclic ligand

Cr^III, Mn^II, Co^II, Ni^II, Cu^II and Pd^II complexes of the macrocyclic ligand, 2,3,5,8,9,11 hexamethyl-1,4,7,10 tetraaza- cyclododeca-1,3,7,9 tetraene (DADAP), have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, i.r., electronic and e.p.r. spectral studies. These spectral studies suggest an octahedral geometry for the Cr^III, Mn^II and Co^II, square planar geometry for Ni^II and Pd^II and tetragonal geometry for Cu^II complexes.     

Coordination behaviour of azines towards iron(II), palladium(II) and platinum(II)

Summary The coordination behaviour of Schiff bases derived from the condensation of some of the heterocyclic aldehydes with hydrazine hydrate, towards Fe^II, Pd^II and Pt^II, has been studied. The 1:1 and 1:2 molar reactions of MCl₂ with the Schiff bases result in coloured solids which have been characterised by elemental analysis, conductance and magnetic measurements. The mode of bonding has been deduced from i.r. and n.m.r. (¹H and¹³C) studies.     

Synthesis,Structures and Spectroscopic Properties of Platinum(II), Palladium(II) and Copper(I) Halide Complexes with Pyrimidine‐phosphine Ligand

The reactions of pyrimidine‐phosphine ligand N‐[(diphenylphosphino)methyl]‐2‐pyrimidinamine ( L ) with various metal salts of Pt^II, Pd^II and Cu^I provide three new halide metal complexes, Pt₂Cl₄(μ‐L)₂·2CH₂Cl₂ ( 1 ), Pd₂Cl₄(μ‐L)₂ ( 2 ), and [Cu₂(μ‐I)₂L₂]_n ( 3 ). Single crystal X‐ray diffraction studies show that complexes 1 and 2 display a similar bimetallic twelve‐membered ring structure, while complex 3 consists of one‐dimensional polymeric chains, which are further connected into a 2‐D supramolecular framework through hydrogen bonds. In the binuclear complexes 1 and 2 , the ligand L serves as a bridge with the N and P as coordination atoms, but in the polymeric complex 3 , both bridging and chelating modes are adopted by the ligand. The spectroscopic properties of complexes 1 ‐ 3 as well as L have been investigated, in which complex 3 exhibits intense photoluminescence originating from intraligand charge transfer (ILCT) π→π* and metal‐to‐ligand charge‐transfer (MLCT) excited states both in acetonitrile solution and solid state, respectively.     

Chromium(III), manganese(II), iron(III), cobalt(II), nickel(II) and copper(II) complexes with a pentadentate, 15-membered new macrocyclic ligand

Complexes of Cr^III, Mn^II, Fe^III, Co^II, Ni^II and Cu^II containing a macrocyclic pentadentate nitrogen–sulphur donor ligand have been prepared via reaction of a pentadentate ligand (N₃S₂) with transition metal ions. The N₃S₂ ligand was prepared by [1 + 1] condensation of 2,6-diacetylpyridine with 1,2-di(o-aminophenylthio(ethane. The structures of the complexes have been elucidated by elemental analyses, molar conductance, magnetic susceptibility measurements, i.r., electronic and e.p.r. spectral studies. The complexes are of the high spin type and are six-coordinate.     

Monomeric dioxouranium(VI), chromium(III), cobalt(II), nickel(II) and copper(II) complexes with primary cellulose acetate (PCA)

Monomeric UO ₂ ²⁺ , Cr^III, CO^II, Ni^II and Cu^II complexes with primary cellulose acetate (PCA) have been prepared and characterized. Infrared,¹H NMR, UV/visible spectroscopy, elemental analysis, therniogravimetry, conductance and magnetic measurements were used to assign the mode of coordination in the isolated species. The investigation revealed that PCA exhibits octahedral coordination with Cr^III, Co^II, Ni^II and a square planar form with Cu^II whereas the UO₂ moiety is virtually linear. PCA acts as a neutral bidentate chelating agent via the two oxygen atoms of the vicinal ester groups in the secondary positions forming a five-membered chelate ring. A comparative study between chelates of PCA and those previously prepared with secondary cellulose acetate (SCA) has been undertaken.     

Synthesis and characterization of a new macrocyclic Schiff base derived from 2,6-diaminopyridine and 1,10-bis(2-formylphenyl)-1,4,7,10-tetraoxadecane and its Cu(II), Ni(II), Pb(II), Co(III) and La(III) complexes

A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:19,20-tribenzo-9,12,15,18-tetraoxacyclounkosa-1,5-diene (L) was synthesized by reaction of 2,6-diaminopyridine and 1,10-bis(2-formylphenyl)-1,4,7,10-tetraoxadecane. Then, its Cu^II, Ni^II, Pb^II, Co^III and La^III complexes were synthesized by the template effect by reaction of 2,6-diaminopyridine and 1,10-bis(2-formylphenyl)-1,4,7,10-tetraoxadecane and Cu(NO₃)₂· 3H₂O, Ni(NO₃)₂· 6H₂O, Pb(NO₃)₂, Co(NO₃)₂· 6H₂O, La(NO₃)₃·6H₂O respectively. The ligand and its metal complexes have been characterized by elemental analysis, IR, ¹H and ¹³C NMR, u.v–vis spectra, magnetic susceptibility, conductivity measurements and mass spectra. All complexes are diamagnetic and the Cu^II complex is binuclear. The Co^III complex was oxidized to Co^III.     

Cobalt(III), copper(II), and nickel(II) complexes of 1-thia-4,7-diazacyclononane-S-oxide

Summary The title complexes [ML₂]ⁿ⁺=Co^III, Cu^II, Ni^II; L=1-thia-4,7-diazacyclononane-S-oxide) have been prepared and characterized spectroscopically. The sulphoxide group is coordinated through the oxygen atom and the complexes have atrans-O,O geometry. The nickel(II) complex of bis(2-amino-ethyl)sulphoxide has also been studied.     

Effect of the degree of sulfoethylation of polyethylenimine on the selectivity of sorption of palladium(ii) from binary solutions

Poly(N-2-sulfoethylethylenimine) (SEPEI) with a degree of modification equal to 0.30, 0.58, and 0.74, cross-linked with diethylene glycol diglycidyl ether, demonstrates efficient sorption properties with respect to Pt^IV, Pd^II, and Au^III ions. The selectivity coefficient K_Pd/Au in a HCl solution with pH 0.8 decreases from 90 to 61, and the selectivity coefficient K_Pd/Pt in a HCl solution with pH 3.9 increases from 0.94 to 480 with an increasing degree of modification. A thiourea hydrochloric acid solution effectively removes metal ions; the desorption of Pt^IV, Pd^II, and Au^III from the SEPEI surface reaches 100, 96.9, and 83.8%, respectively.

     

Untersuchungen zur Alkylierung von Bis-Stilbendithiolato-Komplexen des Ni(II), Pd(II) und Pt(II)

Investigation on the Alkylation of Bis-Stilbendithiolato Complexes of Ni^II, Pd^II, and Pt^II Alkylation reactions of co-ordinated ligands of the type of ethylene-bisthiol R₂S₂C₂²-proceed different depending on the substituents R. The neutral complexes isolated by a alkylation of the nickel bis-chelates (R = phenyl) according to Schrauzer and Rabinowitz and formulated by these authors as mixed ligand chelates of dithiolate and diether, were identified by us as complexes of the monoethers of the ligand. These nickel (II) complexes of the mono-ethers can not be alkylated further by alkyliodides. Oxidative coupling of two ligands yields disulfides which have been identified by mass spectroscopy thus indicating the original position of attack of the alkylating reagent. The formation of bis-monether complexes is reflected by the different charges on the S atoms of the model complex [Ni(CH₃S₂C₂H₂)(S₂C₂H₂)]- obtained from EHT and CNDO calculations. Both possible stereo-isomers have been isolated of the bis-methylmonether complex of Pt(II). Trans-[M((CH₃)(S₂C₂Ph₂))₂] (M = Ni(II), Pd(II)) form CH₂Cl₂ adducts. By treating the Ni-bis complexes of the monoalkylthioethers with iodine polyiodides are prepared. Binuclear Pd(II) complexes of composition [Pd₂((R)(S₂C₂Ph₂))₂Cl₂] could be prepared by metal exchange.     

New complexes of iron(III), cobalt(II), nickel(II) and copper(II) with 2-phenyl-1,2,3-triazole-4-carboxalidene-2-aminophenol

Summary Fe^III, Co^II, Ni^II and Cu^II complexes of a new Schiff base, 2-phenyl-1,2,3-triazole-4-carboxalidene-2-aminophenol (PTCAP), have been synthesized and characterized by elemental analyses, molar conductance and magnetic susceptibility measurements, and by u.v.-vis., i.r. and e.p.r. spectral observations. The studies indicate an octahedral structure for the complexes with the general formula [ML₂] (M = Co^II, Ni^II or Cu^II.; L = PTCAP) or [M′(OH)L₂] (M′ = Fe^III). The i.r. spectra suggest that the ligand acts as a tridentate (NNO) donor towards Co^II, Ni^II and Cu^II, and, in the Fe^III complex, one of the two ligand molecules acts as a bidentate (NO) donor and the other as a tridentate donor. The M?ssbauer spectrum of the Fe^III complex suggests the presence of a spin equilibrium at room temperature. Cyclic voltammograms are also recorded for the Cu^II and Fe^III complexes.     

Can Serendipity Still Hold Any Surprises in the Coordination Chemistry of Mixed-Donor Macrocyclic ligands? The Case Study of Pyridine-Containing 12-Membered Macrocycles and Platinum Group Metal ions PdII,PtII, and RhIII

This study investigates the coordination chemistry of the tetradentate pyridine-containing 12-membered macrocycles L¹-L³ towards Platinum Group metal ions Pd^II, Pt^II, and Rh^III. The reactions between the chloride salts of these metal ions and the three ligands in MeCN/H₂O or MeOH/H₂O (1:1 v/v) are shown, and the isolated solid compounds are characterized, where possible, by mass spectroscopy and ¹H- and ¹³C-NMR spectroscopic measurements. Structural characterization of the 1:1 metal-to-ligand complexes [Pd(L¹)Cl]₂[Pd₂Cl₆], [Pt(L¹)Cl](BF₄), [Rh(L¹)Cl₂](PF₆), and [Rh(L³)Cl₂](BF₄)·MeCN shows the coordinated macrocyclic ligands adopting a folded conformation, and occupying four coordination sites of a distorted square-based pyramidal and octahedral coordination environment for the Pd^II/Pt^II, and Rh^III complexes, respectively. The remaining coordination site(s) are occupied by chlorido ligands. The reaction of L₃ with PtCl₂ in MeCN/H₂O gave by serendipity the complex [Pt(L³)(μ-1,3-MeCONH)PtCl(MeCN)](BF₄)₂·H₂O, in which two metal centers are bridged by an amidate ligand at a Pt1-Pt2 distance of 2.5798(3) Å and feature one square-planar and one octahedral coordination environment. Density Functional Theory (DFT) calculations, which utilize the broken symmetry approach (DFT-BS), indicate a singlet d⁸-d⁸ Pt^II-Pt^II ground-state nature for this compound, rather than the alleged d⁹-d⁷ Pt^I-Pt^III mixed-valence character reported for related dinuclear Pt-complexes.     

Synthesis and crystal structure determination of copper(II) and iron(III) complexes of 2-(2-pyridyl)benzothiazole

Two complexes [Cu^II(pbt)(dmf)Cl₂] and [Fe^III(pbt)Cl₃], where pbt is 2-(2-pyridyl)benzothiazole, and dmf is dimethylformamide, were prepared by the reaction of metal chlorides with pbt solutions. The structures of the products were identified by elemental analysis, usual spectroscopic methods and X-ray diffraction analysis. The crystal data revealed penta-coordination around both metal ions, with trigonal bipyramidal geometries. 2-(2-pyridyl)benzothiazole binds to both Cu^II and Fe^III in the N,N-chelation manner and leaves the S atom uncoordinated.     

Square planar complexes of nickel(II), palladium(II) and platinum(II) with 1-(2-hydroxyphenyl)-3,5-diphenylformazan

Summary A novel series of formazan complexes of general formula FoML [H₂Fo = 1-(2-hydroxyphenyl)-3,5-diphenylformazan; M = Ni^II, Pd^II or Pt^II; L = NH₃, py and Ph₃P] are described. The formazan nickel(II) system shows linkage isomerism; one isomer, A, contains an unusual five-membered formazan chelate ring, whereas the other, isomer B, has the usual six-membered ring.¹³C n.m.r., u.v. and i.r. spectra are presented and interpreted. From these the palladium and platinum complexes appear to contain the six-membered ring of the B type isomer.     

Ligational behaviour of two biologically active N−S donors towards cobalt(III), iron(III), iron(II) and rhodium(III)

Summary The chelating behaviour of two biologically active ligands, pyridine-2-carboxaldehyde(4-phenyl) thiosemicarbazone(L₁H) and pyridine-2-carboxaldehyde thiosemicarbazone(LH), towards Fe^III, Co^III, Fe^II and Rh^III has been investigated. The ligands act as tridentate N–N–S donors, resulting in the formation of bis-chelate complexes of the type M^III(A)₂X·nH₂O (A=L₁ or L; X=Cl, ClO₄; M=Co^III, Rh^III, Fe^III), Fe^II(L₁H)₂SO₄·2H₂O and Fe^II(L₁)₂·H₂O. Biological activity of the ligands and the metal complexes in the form ofin vitro antibacterial activities towardsE. coli has been evaluated and the possible reasons for enhancement of the activity of ligands on coordination to metal ion is discussed.     

Spectral and structural studies of cobalt(II,III), nickel(II), and copper(II) complexes of dehydroacetic acid N4-dialkyl- and 3-azacyclothiosemicarbazones

Co^II,III, Ni^II, and Cu^II complexes of new dehydroacetic acid N4-substituted thiosemicarbazones have been studied. The substituted thiosemicarbazones, N4-dimethyl-(DA4DM), N4-diethyl-(DA4DE), 3-piperidyl-(DApip) and 3-hexamethyleneiminyl-(DAhexim), when reacted with the metal chlorides, produced two Co^II complexes, [Co(DA4DE)Cl₂] and [Co(DAhexim)₂Cl₂]; two Co^III complexes, [Co(DA4DM-H)₂Cl] and [Co(DApip-H)(DApip-2H)]; a paramagnetic Ni^II complex, [Ni(DAhexim)(DAhexim-H)Cl]; three diamagnetic Ni^II complexes, [Ni(DA4DM-H)Cl], [Ni(DA4DE-H)Cl] and [Ni(DApip-H)Cl]; and four Cu^II complexes with the analogous stoichiometry of the latter three Ni^II complexes. These new thiosemicarbazones have been characterized by their melting points, as well as i.r., electronic and ¹H-n.m.r. spectra. The metal complexes have been characterized by i.r. and electronic spectra, and when possible, n.m.r. and e.s.r. spectra, as well as elemental analyses, molar conductivities, and magnetic susceptibilities. The crystal and molecular structure of the four-coordinate Cu^II complex, [Cu(DAhexim-H)Cl] has been determined by single crystal X-ray diffraction and the anionic ligand coordinates via an oxygen of the dehydroacetic acid and the thiosemicarbazone moiety's imine nitrogen and thione sulfur.