Transition metal complexes with neutral and deprotonated malonamide

Summary New complexes of the general formulae [M(LH₂)₂Cl₂] (M = Mn, Fe, Co, Ni, Cu, Zn), [Mn(LH₂)₂X₂] (X = Br, I), [Cu(LH₂)₂Br₂], [Ni(LH₂)₂X₂] (X = Br, NCS, ONO₂), [Cu(LH₂)X₂]_n (X = Cl, Br), K₂[NiL₂]·2H₂O and K₂-[CuL₂]·H₂O, where LH₂ = malonamide, were isolated. The complexes were characterized by elemental analyses, X-ray powder patterns, magnetic susceptibilities and spectroscopic (variable-temperature ⁵⁷Fe-Mössbauer, e.s.r., u.v.-vis., i.r., far-i.r., Raman) studies. Monomeric trans pseudo-octahedral stereochemistries for the neutral 12 complexes and square planar structures of D _2h symmetry for the two ionic complexes are assigned in the solid state. Dimeric or polymeric five-coordinate structures are proposed for the 11 copper(II) compounds. LH₂ and L^2– behave as bidentate chelating ligands binding through oxygen and deprotonated nitrogen atoms, respectively. A detailed comparison of the studied complexes with the corresponding oxamide complexes is also presented.     

Reactions of metal carbonyl derivatives : XIV. Bridged phosphido derivatives of iron and ruthenium

The tertiary phosphines P(C₆H₅)₂R [RM π-C₅H₅)(CO)₂ M(π-C₅H₅(CO)₂ (M = Fe or Ru)] readily effect the displacement of the chloro group in [M′(φ-C₅H₅)(CO)₂Cl] (M′ = Fe or Ru) to give bridged cationic species of the type [MM′(φ-C₅H₅)₂(CO)₄P(C₆H₅)]⁺. Treatment of [Fe₂(CO)₉] with P(C₆H₅)₂R [RRu(φ-C₅H₅)(CO)₂] leads to the formation of the neutral mixed-metal derivatives [FeRu(φ-C₅H₅)(CO)₆P(C₆H₅)₂] and [FeRu(φ-C₅H₅)(CO)₅P(C₆H₅)₂].     

Reactions of Lewis bases with tetrakisdiphenylamide uranium(IV)

The coordinatively unsaturated uranium(IV) complex U[N(C₆H₅)₂]₄ has been prepared via the stoichiometric reaction of diphenylamine with [(Me₃Si)₂N]₂ H₂. U[N(C₆H₅)₂]₄ coordinates Lewis bases such as Et₂O, THF, pyridine or (EtO)₃PO, based on electronic absorption spectroscopy and ¹H NMR studies. Exchange between U[N(C₆H₅)₂]₄ and U[N(C₆H₅)₂]₄(L), where L is THF or pyridine, is rapid on the NMR time-scale between 307 and 323 K. Measurement of equilibrium constants for L = THF provides ΔH and ΔS values of −60 kJ mol⁻¹ and −1.8 × 10² J K⁻¹ mol⁻¹, respectively. U[N(C₆H₅)₂]₄ coordinates and binds (EtO)₃PO much more tightly (K_eq = & > 10⁴ M⁻¹) than THF or pyridine with the exchange rate between U[N(C₆H₅)₂]₄ and U[N(C₆H₅)₂]₄[OP(OEt)₃] being close to the NMR time-scale.     

Transition metal(II) ions with dinegative tetradentate schiff base

Some new coordination polymers of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), obtained from the interaction of metal acetate with dipotassium salt of N,N’-di(carboxyethylidene)terephthalaldehydediimine (K₂SB) are described. The products, which have been characterized by elemental analyses, magnetic measurements, thermogravimetric analyses, electronic and infrared spectral studies, have composition, [M(SB)(H₂O)₂]_n. These colored coordination polymers are non-hygroscopic and quite stable at room temperature. On the basis of analytical data and IR studies, a 1:1 metal to ligand stoichiometry has been suggested to these coordination polymers. The IR studies have also revealed that ligands are coordinated to metal ion through carboxy oxygen and azomethine nitrogen. All the studies suggested tetradentate nature of the ligand with octahedral symmetry of the coordination polymers. All the coordination polymers are insoluble in acetone, ethanol, chloroform, methanol, benzene, DMF and DMSO. The thermal decomposition of the coordination polymers is studied and indicates that not only the coordinated water is lost but also that the decomposition of the ligand from the coordination polymers is necessary to interpret the successive mass loss.     

Complexation of tris(pentafluorophenyl)silanes with neutral Lewis bases

A detailed analysis of monodentate and bidentate complexation of tris(pentafluorophenyl)silyl (TPFS) derivatives with neutral Lewis bases was performed. The NMR spectroscopy and X-ray diffraction analysis (11 structures) were the key methods to characterize tetra- or pentacoordinate silicon compounds, whereas the peculiarities of crystal packing were analyzed by means of DFT calculations. The interaction of TPFS-X (X = F, Cl, OTf) with strong Lewis bases (HMPA, N-methylpyrrolidinone) may afford three different species: neutral pentacoordinate TPFS(X)-L, cationic tetracoordinate TPFS-L⁺ X⁻, and cationic pentacoordinate TPFS-(L)⁺₂X⁻, representatives of each type were characterized by X-ray diffraction. A variety of complexes with bidentate complexation, featuring the trigonal bipyramidal geometry with apical C₆F₅-group was prepared and structurally characterized. The extent of Si-C_apical bond elongation depends on the donating ability of the coordinating ligand, with the longest Si-C bond of 1.981(1) Å observed for six-membered complex of TPFS-ether of N-(2-hydroxybenzoyl)pyrrolidine.     

Transition metal derivatives of arene diazonium ions : X. Four-coordinate arenediazo derivatives of iron(−II) and cobalt(−)

The first arenediazo derivatives of iron(?II), Fe(N₂Ar)(NO)(CO)(PPh₃), have been synthesised and their properties are described. A linear relationship has been found between v(CO) in these complexes and η^? for the para substituent in the arenediazo aryl ring. The ⁵⁷Fe Mössbauer spectra of the complexes indicate that [ArN₂]⁺ is a stronger σ-donor and weaker π-acceptor than [NO]⁺. The relationship between ΔE_q and σ_p^? suggests that changes in ΔE_q with aryl substitution involve both substituent-specific and substituent-independent effects. The unstable cobalt(?I) compound Co(N₂C₆H₅)(CO)₂(PPh₃), the first arenediazo derivative of cobalt, is also described.     

Copper(II) complexes with neutral Schiff bases: Syntheses, crystal structures and DNA interactions

The synthesis and X-ray structural characterisation of a new Cu(II) complex, [Cu(L¹)Cl](ClO₄)·CH₃OH (1) [L¹ = N,N′-bis((pyridine-2-yl)phenylidene)-1,3-diaminopropan-2-ol], has been described in this work. The structural study reveals that the Cu(II) centre in 1 has a square pyramidal geometry with a trigonality index τ = 0.43, being coordinated by the organic ligand and a chloro group. The interaction of complex 1 and another complex previously reported by our group, [Cu(L²)](ClO₄)₂ (2) [L² = N-(1-pyridin-2-yl-phenylidene)-N′-[2-({2-[(1-pyridin-2-ylphenylidene)amino]ethyl}amino)ethyl]ethane-1,2diamine], with calf thymus DNA (CT-DNA) has been investigated using absorption and emission spectral studies. The binding constant (K_b) and the linear Stern-Volmer quenching constant (K_sv) have been determined.     

Ternary complexes of 3d metal(II) ions with acetylacetone and salicylaldoxime

Summary New ternary complexes of first-row transition metal ions of composition [M(salox)(acac)] [where M=VO^IV, Mn^II, Co^II, Cu^II and Zn^II, acacH=acetylacetone, saloxH=salicylaldoxime] and their bis-pyridine adducts have been prepared. Molar conductivity measurements indicate that the complexes are non-electrolytes, while magnetic and electronic spectral studies show an essentially octahedral stereochemistry except for the nickel(II) complex which exhibits a square planar-octahedral equilibrium. The e.s.r. spectra show that the complexes are monomeric in CHCl₃ solution.     

Transition metal(II) complexes of (E)-cinnamoylferrocene (S)-methylcarbodithioylhydrazone

A new organometallic ligand, (E)-cinnamoylferrocene (S)-methylcarbodithioylhydrazone (HCfmc) and six transition metal(II) complexes thereof M(Cfmc)2·nH2O (M=Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Hg2+; n=0–2) have been prepared and characterized by elemetal analyses, i.r., u.v., 1H-n.m.r. spectra, electrochemical properties, fluorescence spectra and molar conductances. The HCfmc ligand acts as a bidentate donor, coordinating to the metal ions via nitrogen and sulfur atoms with a trans-configuration.     

Reactions of metal(II) ions with sugar α-amino acids: nickel(II) complexes containing an α-amino acid derived from galactose or mannose

Summary The reaction of Ni^II ions with 2-(benzylamino)-2-deoxy-d-glycero-l-gluco. heptonic acid (BnGa:C₁₄H₂₁NO₇) or 2-(benzylamino)-2-deoxy-d-glycero-d-talo heptonic acid (BnMa:C₁₄H₂₁NO₇) in water yields complexes of formulae [Ni(BnGa)₂(H₂O)₂] and [Ni(BnMa)₂]·2H₂O, respectively, which were characterized by elemental analysis, spectral techniques (u.v.-vis.-n.i.r. and i.r.), magnetic susceptibility measurements, thermal measurements (t.g. and d.s.c.) and X-ray powder diffraction. Both complexes are octahedral with two positions of the coordination sphere occupied by nitrogen atoms. Moreover, in [Ni(BnMa)₂]·2H₂O four oxygen atoms of bridging carboxylate groups are coordinated to the metal ion, while in [Ni(BnGa)₂(H₂O)₂] only an oxygen atom of each carboxylate group is bound to Ni^II. In this case, the coordination is completed via two water molecules.     

Ethers as ligands. Part VI. Transition metal(II) complexes with 18-crown-6

Summary Seven new coordination compounds are reported with the cyclicpolyether 18-crown-6 as the ligand,viz. [Mg(18-crown-6) (H₂O)₂](SbCl₆)₂, [M(18-crown-6)(MeNO₆)₂](SbCl₆)₂ with M is Ca²⁺ and Sr²⁺, [M(18-crown-6)(MeNO₂)](SbCl₆)₂ with M is Mn²⁺ and Co²⁺, and [M(18-crown-6)](SbCl₆)₂ with M is Ni²⁺ and Zn²⁺.     

Interactions between metal ions and carbohydrates. Coordination behavior of neutral erythritol to Ca(II) and lanthanide ions

The study of the sugar-metal ion interactions remains one of the main objectives of carbohydrate coordination chemistry because the interactions between metal ions and carbohydrates are involved in many biochemical processes. This paper presents a comparison of coordination structures of erythritol with alkaline-earth-metal and lanthanide chloride and nitrate in the solid state using FT-IR and X-ray diffraction. Neutral, nondeprotonated erythritol (E) reacts with CaCl(2) to give three CaCl(2)(-)erythritol (CaE(I), CaE(II), CaE(III)) complexes, showing that three of the five general features of calcium-carbohydrate complexes deduced in the reference encounter contrary examples. Different coordination structures have been observed for calcium and lanthanide chloride and nitrates. The coordination of carbohydrates to metal ions is complicated, and erythritol, chloride ions, nitrates, water molecules, and ethanol (crystallization medium and reaction solvents) have the chance to coordinate to metal ions. IR spectral results show that different lanthanide ions, from LaCl(3) to TbCl(3), have similar coordination structures with erythritol. The results show that erythritol can act as two bidentate neutral ligands (CaE(I), CaE(II), CaE(III), CaEN, PrE, NdE) or as a three-hydroxyl donor (NdEN). The IR results are consistent with the crystal structures.     

Insertion of acrylonitrile into palladium methyl bonds in neutral and anionic Pd(II) complexes

The reactions of a series of Pd(II) methyl compounds of general formula LPd(NCCH(3))CH(3), where L is a bulky phenoxydiazene or phenoxyaldimine ligand with the polar olefin acrylonitrile (AN), are reported. The compounds react with an excess of AN to give the products of 2,1 insertion into the Pd-Me bond, yielding dimers and/or trimers which feature bridging alpha-cyano groups. The reactions were studied by low temperature (1)H NMR spectroscopy, revealing an initial formation of compounds featuring N-bound AN, which isomerized to an (unobserved) pi-bound species that rapidly underwent 2,1 insertion into the Pd-Me bond. Intermediate oligomeric complexes retaining a Pd-Me function were observed at low [AN] in these reactions. Under pseudo first-order conditions, k(obs) values of 8.5 x 10(-5) to 2.68 x 10(-3) M(-1) (-22 degrees C to 10 degrees C, 100 equiv of AN) and activation parameters of DeltaH++ = 14.4(5) kcal mol(-1) and DeltaS++ = -19(5) eu were obtained in one case. Comparison of the overall rates of insertion between two LPd(NCCH(3))CH(3), differing in the overall charge on the supporting ligand L, showed that the complex bearing a negatively charged ligand reacts with AN twice as fast as one with no anionic charge. The rates of insertion in both of these complexes are significantly faster than reported rates for analogous reactions in cationic Pd(II) derivatives, indicating that increasing the negative charge on the complex enhances the rate of AN insertion. These results provide fundamental mechanistic insights into a crucial reaction for incorporation of polar comonomers into alpha olefins via a coordination polymerization mechanism.     

Preparation and properties of anionic transition metal complexes containing triheterocarbenium ions

Summary Thermally stable anionic tetracarbonylcobalt complexes containing triheterocarbenium ions, [Co(CO)₄]^–[cation]⁺, have been synthesized by the ion exchange reaction of [Co(CO)₄]^–PPN⁺ with the corresponding carbenium ions. Similar molybdenum complexes containing cyclopentadienyl and carbonyl ligands were also prepared. The complexes were characterized by elemental analyses and by i.r. and n.m.r. spectroscopies. The ionic structures of the complexes are confirmed on the basis of their large electric conductivities.     

Synthesis,structural characterization and biological activities of metal(II) complexes with Schiff bases derived from 5-bromosalicylaldehyde: Ru(II) complexes transfer hydrogenation

In this study, two novel Schiff base ligands (L¹ and L²) derived from condensation of methyl 2-amino-6-methyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylate and methyl 2-amino-6-phenyl-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate, both starting matter with 5-bromo-salicylaldehyde, and their Zn(II) and Ni(II) metal complexes have been prepared using a molar ratio of ligand:metal as 1:1 except the Ru(II) complexes 1:0.5. The structures of the obtained ligands and their metal complexes were characterized by elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, UV–vis, thermal analysis methods, mass spectrometry, and magnetic susceptibility measurements. Antioxidant and antiradical activity of Schiff base ligands and their metal complexes were been evaluated in vitro tests. Antioxidant activities of metal complexes generally were more effectives than free Schiff bases. 1c and 2c were used as catalysts for the transfer hydrogenation (TH) of ketones. 1c, 2c complexes were found to be efficient catalyst for transfer hydrogenation reactions.     

Transition metal complexes of the Schiff bases derived from S-alkyldithiocarbazate with 2-pyridinecarboxaldehyde N-oxide—I. Synthesis, properties and structure of four-coordinate copper(II) complexes

Two new Schiff bases (SMPDH and SBPDH) of S-methyl- and S-benzyl-dithiocarbazate with 2-pyridinecarboxaldehyde N-oxide were prepared and confirmed by elemental analyses and IR spectra. Four copper(II) complexes of the above two Schiff base ligands with imidazole and pyridine were obtained and characterized spectroscopically. The crystal structure of [Cu(SMPD)ImH]ClO₄ was determined by X-ray diffraction analysis. The geometry of the copper atoms in these complexes is square planar with an unsymmetrical environment.     

Fluorinated barrelene-ruthenium(II) complexes with anionic chelating ligands

Reaction of ruthenium(III) chloride with the barrelene diolefins (tetrafluoro-benzobarrelene (TFB) or (trimethyltetrafluorobenzobarrelene) (Me₃ TFB) leads to the formation of the polymeric complexes [RuCl₂(barrelene)]_n. These compounds react with anionic chelating ligands with formation of new hexacoordinated neutral complexes of the general formulae [Rh(chelate)₂(barrelene)], where chelate = acetylacetonate, tropolonate, salicylal-dehydate and 8-oxyquinolinate. The IR and ¹H NMR spectra of the complexes are given and discussed.     

Transition metal complexes with thiosemicarbazide-based ligands. Part 56. Square-pyramidal complexes of copper(II) with 2-acetylpyridine S-methylisothiosemicarbazone

The article describes the synthesis and single-crystal X-ray analysis of two sulfato and one thiocyanato copper(II) complex with 2-acetylpyridine S-methylisothiosemicarbazone (HL) of the formulae [Cu(HL)SO₄(H₂O)]·H₂O (1), [Cu₂(HL)₂(μ-SO₄)₂]·2H₂O (2) and [Cu(HL)(NCS)(SCN)] (3), as well as the structure of the protonated ligand H₂L⁺I⁻. Complexes 1 and 2 were obtained from the reaction of aqueous/methanolic CuSO₄·5H₂O and ethanolic/methanolic H₂L⁺I⁻ solutions, respectively. Complex 3 was synthesized by the reaction of methanolic solutions of Cu(ClO₄)₂·6H₂O, the ligand and NH₄SCN, with the addition of triethyl orthoformate. All three complexes have a slightly deformed square-pyramidal structure (τ_av = 0.15) with the tridentate NNN neutral ligand in the basal plane. In complexes 1 and 3 the apical position is occupied by the oxygen atom of the monodentate SO₄ group, or the sulfur atom of the SCN group. Thanks to the hydrogen bonds, complex 3 may be thought of as having a pseudo-dimeric structure. In the authentic centrosymmetric dimer 2, the oxygen atoms of both SO₄ groups occupy also the apical position of both coordination polyhedra, as well as an equatorial position. Complexes 1 and 3 have μ_eff values characteristic of magnetically isolated mononuclear Cu(II) complexes. In contrast to them, complex 2 has a μ_eff value of 1.57 BM, which is in agreement with its dinuclear structure. All the complexes, in addition to the X-ray analysis and magnetic measurements, were characterized by IR and UV–Vis spectroscopy and by thermal analysis.