Synthesis,crystal structure and catalytic performance of bis (imino)pyridyl nickel complexes

Two new Ni(II) complexes of 2,6-bis[1-(2,6-diethylphenylimino)ethyl]pyridine (L¹), 2,6-bis[1-(4-methylphenylimino)ethyl]pyridine (L² ) have been synthesized and structurally characterized. Complex Ni(L¹)Cl₂?·?CH₃CN (1), exhibits a distorted trigonal bipyramidal geometry, whereas complex Ni(L¹)(CH₃CN)Cl₂ (2), is six-coordinate with a geometry that can best be described as distorted octahedral. The catalytic activities of complexes 1, 2, Ni{2,6-bis[1-(2,6-diisopropyl-phenylimino)ethyl]pyridine} Cl₂?·?CH₃CN (3), and Ni{2,6-bis[1-(2,6-dimethylphenylimino) ethyl]pyridine}Cl₂?·?CH₃CN (4), for ethylene polymerization were studied under activation with MAO.     

Synthesis and crystal structures of two (cyclopentadienyl)titanium(III) hydroborate complexes, [CpTiCl(BH4)]2 and Cp2Ti(B3H8)

Treatment of Cp^∗TiCl₃ and Cp₂TiCl₂ with NaB₃H₈ affords the titanium(III) hydroborate compounds [Cp^∗TiCl(BH₄)]₂ and Cp₂Ti(B₃H₈), respectively. The former compound arises by means of a new reaction, the metal-induced fragmentation of the B₃H₈ anion, and can also be made by treating Cp^∗TiCl₃ with LiBH₄. The latter compound has been previously described, but not characterized crystallographically. Both compounds have been studied by single crystal X-ray diffraction. Dimeric [Cp^∗TiCl(BH₄)]₂ has bridging chloride ligands and terminal Cp^∗ and BH₄ ligands. The Ti-Ti distance is 3.452(1) Å, which indicates that there is no metal-metal bonding interaction. The Ti-Cl distances are 2.440(2) Å and the Ti-Cl-Ti and Cl-Ti-Cl angles of 89.97(8) and 90.03(8)° so that the Ti₂Cl₂ unit is nearly a perfect square. The BH₄ groups are each tridentate, with a Ti-B distance of 2.220(9) Å and an average Ti-H distance of 1.98(5) Å. In Cp₂Ti(B₃H₈), the B₃H₈ ligand is bidentate, as is usually seen, and the Ti-B and Ti-H distances are 2.600(3) and 1.96(2) Å. The dihedral angle between the Ti-B(1)-B(2) plane and the B(1)-B(2)-B(3) plane is 123.4°. The Ti-B distances are 0.04 Å longer than those in niobium analog, Cp₂Nb(B₃H₈), despite the fact that the single bond metallic radius of Ti is 0.02 Å smaller than that of Nb. This lengthening of the bond is probably a consequence of the presence of one fewer skeletal bonding electron in Cp₂Ti(B₃H₈).     

Novel ternary cobalt(II) and nickel(II) complexes of N-phthaloylglycinate. Synthesis, characterization and X-ray crystal structure

A new series of N-phthaloylglycineate (N-phthgly) ternary complexes of cobalt(II) and nickel(II) with imidazole (imi), N-methylimidazole (mimi) and 2,2′-bipyridyl (bipy) have been synthesized and characterized by elementary analyses, IR spectroscopy, thermogravimetric analysis. X-ray crystal structure analyses of the three complexes of [Co(mimi)₂(N-phthgly)₂] (1), [Co(bipy)(OH₂)₄](N-phthgly)₂ (2) and [Ni(imi)₂(N-phthgly)₂(OHCH₃)₂] (3) were also carried out. In complex (1), the Co(II) exists in a distorted tetrahedral enviroment, where two nitrogen atoms of two methylimidazole molecules and two oxygen atoms of the carboxylate group of two N-phthaloylglycinate molecules are coordinated. On the other hand, in complex (2) the cobalt atom coordinates a 2,2′-bipyridine molecule and four water oxygen atoms forming a distorted octahedral conformation. A molecule of N-phthaloylglycinate is connected by van der waals contact and H-bonds. For complex (3), the nickel atom is surrounded by four oxygens (two oxygens of two different N-phthaloylglycinate molecules and two of methanol ligand) in the basal plane of octahedron along with two imidazole nitrogen atoms at the apical positions. Strong intramolecular H-bond exists between the uncoordinated carboxylic oxygen of the N-phthaloylglycinate ligand and the O–H of the methanol group.     

Synthesis and structures of binuclear half-sandwich cobalt (III) ortho-carboranedithiolato complexes with silyl-bridged bis(cyclopentadienyl) ligands

Five binuclear half-sandwich cobalt complexes, [(η⁵-C₅H₄)Co(CO)I₂]₂SiMe₂ (3), [(η⁵-C₅H₄)Co(S₂C₂B₁₀H₁₀)]₂SiMe₂ (4), [(η⁵-C₅H₄)]₂Co₂(μ₂-S₂C₂B₁₀H₁₀)SiMe₂ (5), [(η⁵-C₅H₃)CoI₂](μ-I)[(η⁵-C₅H₃)Co(CO)I](SiMe₂)₂ (8), [(η⁵-C₅H₃)Co(S₂C₂B₁₀H₁₀)]₂(SiMe₂)₂ (9), were successfully synthesized in moderate yield by the reactions of corresponding ligands, (C₅H₅)₂SiMe₂ (1) and (C₅H₄)₂(SiMe₂)₂ (6), respectively. The molecular structures of 3, 5, 6, 8 and 9 was determined by X-ray crystallographic analysis, which distinctly depict various molecular structures containing the Cp rings and the metal centers with halide or 1,2-dicarba-closo-dodecaborane-1,2-dithiolato ligands. For the (η⁵-C₅H₄)₂SiMe₂ complexes, coordination of the fragments CpCo favors a exo conformation. With the rigid structure of the di-bridged ligand (C₅H₄)₂(SiMe₂)₂, only cis isomers of the corresponding (η⁵-C₅H₃)₂(Si₂Me₂)₂ complexes are formed. All the complexes have been well characterized by elemental analysis, NMR and IR spectra.     

Reactions of bis(η4-1,5-cyclooctadiene)nickel(0) with transition metal halides,and the crystal structure of μ-dichloro-bis(tetrahydrofuran)hexacarbonyldimanganese

Bis-(η⁴-1,5-cyclooctadiene)nickel(0) reacted with η⁵-C₅H₅Fe(CO)₂Cl, η³-C₅H₅Fe(CO)₃Cl, Mn(CO)₅Cl and {Mn[P(OMe)₃](CO)₄}₂ to form metal metal bonded coupling products. Partial reduction of Mn(CO)₅Cl gave [MnCl(CO)₃(THF)]₂ shown to have a chlorine-bridged C_2h structure by X-ray diffraction analysis. Ligand transfer also accompanied the reduction of Fe[P(OMe)₃]₂(CO)₂Br₂ and Fe(CO)₄Cl₂ to Fe[P(OMe)₃]₂(CO)₃ and Fe(CO)₅, respectively. Only partial reduction was observed for Ti(acac)₂Cl₂ and (η⁵-C₅H₅)₂TiCl₂ which gave [Ti(acac)₂Cl]₂ and (η⁵-C₅H₅)₂Ti(py)Cl, respectively.     

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.     

Synthesis and crystal structures of (C8h8)Nd(C5H9C5H4) (THF)2 and [(C8H8)Gd(C5H9C4H4(THF)][(C8H8)GD(C5H9C5H4(THF)2]

LnCl₃ (Ln=Nd, Gd) reacts with C₅H₉C₅H₄Na (or K₂C₈H₈) in THF (C₅H₉C₅H₄ = cyclopentylcyclopentadienyl) in the ratio of 1 : to give (C₅H₉C₅H₄)LnCl₂(THF)_n (orC₈H₈)LnCl₂(THF)_n], which further reacts with K₂C₈H₈ (or C₅H₉C₅H₄Na) in THF to form the litle complexes. If Ln=Nd the complex (C₈H₈)Nd(C₅H₉C₅H₄)(THF)₂ (a) was obtained: when Ln=Gd the 1 : 1 complex [(C₈H₈)Gd(C_%H₉)(THF)][(C₈H₈)Gd(C₅H₉H₄)(THF)₂] (b) was obtained in crystalline form.

The crystal structure analysis shows that in (C₈H₈)Ln(C₅H₉C₅H₄)(THF)₂ (Ln=Nd or Gd), the Cyclopentylcyclopentadieny (η⁵), cyclooctatetraenyl (η⁸) and two oxygen atoms from THF are coordinated to Nd³⁺ (or Gd³⁺) with coordination number 10.

The centroid of the cyclopentadienyl ring (Cp′) in C₅H₉C₅H₄ group, cyclooctatetraenyl centroid (COTL) and two oxygens (THF) form a twisted tetrahedron around Nd³⁺ (or Gd³⁺). In (C₈H₈)Gd(C₅H₉C₅H₄)(THF), the cyclopentyl-cyclopentadienyl (η⁵), cyclooctatetraenyl (η⁸) and one oxygen atom are coordinated to Gd³⁺ with the coordination number of 9 and Cp′, COT and oxygen atom form a triangular plane around Gd³⁺, which is almost in the plane (dev. -0.0144 Å).     

Effect of the organic fragment on the mesogenic properties of a series of organogold(I) isocyanide complexes. X-ray crystal structure of [Au(CCC5H4N)(CNC6H4O(O)CC6H4OC10H21)]

Rod-like organogold(I) complexes [AuR(CNC₆H₄O(O)CC₆H₄OC₁₀H₂₁-p)] were prepared and their liquid crystal behaviour was studied. Depending on the nature of R, the synthetic methodology was different. Thus, for R = substituted alkynyl ligands, the new compounds were prepared in two steps:(i) reaction of [AuCl(tht)] (tht = tetrahydrothiophene) with R′CCH(R′ = C₅H₄N, C₆H₄CN, C₆H₄CCC₅H₄N) in the presence of NaOAc to give insoluble [Au(CCR′)]_n; (ii) reaction of the latter polymers with the isonitrile CNC₆H₄O(O)CC₆H₄OC₁₀H₂₁-p.For R = fluorinated aryls, the complexes were prepared by displacement of tht from the compounds [AuR(tht)] (R = C₅F₄N, C₆F₄C₅H₄N, C₆F₅) with isonitrile.In addition, an unexpected ionic derivative [Au(CCC₅H₄NC₁₀H₂₁)₂][Au(CCC₅H₄N)₂] was formed in the reaction between [PPh₄][Au(CCC₅H₄N)₂] and C₁₀H₂₁I. All these compounds have been characterized by IR and NMR spectroscopy and mass spectrometry. The X-ray crystal structure of the compound with R = CCC₅H₄N shows a linear molecule in which the gold atom is surrounded by the pyridine-containing acetylene and the isonitrile ligand, and no direct gold-gold interaction occurs. Six of the neutral compounds are liquid crystals and their optical, thermal and thermodynamic data were analyzed and compared in terms of molecular polarizability.     

Binuclear half-sandwich cobalt(III) and rhodium(III) ortho-carboranedichalocogenolato complexes with ether chain-bridged bis(cyclopentadienyl) ligand

1, 1'-(3-Oxapentamethylene)dicyclopentadiene [O(CH(2)CH(2)C(5)H(5))(2)], containing a flexible chain-bridged group, was synthesized by the reaction of sodium cyclopentadienide with bis(2-chloroethyl) ether through a slightly modified literature procedure. Furthermore, the binuclear cobalt(III) complex O[CH(2)CH(2)(eta(5)-C(5)H(4))Co(CO)I(2)](2) and insoluble polynuclear rhodium(III) complex {O[CH(2)CH(2)(eta(5)-C(5)H(4))RhI(2)](2)}(n) were obtained from reactions of with the corresponding metal fragments and they react easily with PPh(3) to give binuclear metal complexes, O[CH(2)CH(2)(eta(5)-C(5)H(4))Co(PPh(3))I(2)](2) and O[CH(2)CH(2)(eta(5)-C(5)H(4))Rh(PPh(3))I(2)](2), respectively. Complexes react with bidentate dilithium dichalcogenolato ortho-carborane to give eight binuclear half-sandwich ortho-carboranedichalcogenolato cobalt(III) and rhodium(III) complexes O[CH(2)CH(2)(eta(5)-C(5)H(4))Co(PPh(3))(E(2)C(2)B(10)H(10))](2) (E = S and Se), O[CH(2)CH(2)(eta(5)-C(5)H(4))](2)Co(2)(E(2)C(2)B(10)H(10)) (E = S and Se), O[CH(2)CH(2)(eta(5)-C(5)H(4))Co(E(2)C(2)B(10)H(10))](2) (E = S and Se and O[CH(2)CH(2)(eta(5)-C(5)H(4))Rh(PPh(3))(E(2)C(2)B(10)H(10))](2) (E = S and Se). All complexes have been characterized by elemental analyses, NMR spectra ((1)H, (13)C, (31)P and (11)B NMR) and IR spectroscopy. The molecular structures were determined by X-ray diffractometry.     

Binuclear vanadium(V) complexes of bis(aryl)adipohydrazone: synthesis,spectroscopic studies,crystal structure and catalytic activity

Three new binuclear vanadium(V) complexes of bis(aryl)adipohydrazones (H₄L¹ = bis((2-hydroxynaphthalen-1-yl)methylene)adipohydrazide, H₄L² = bis(5-bromo-2-hydroxybenzylidene)adipohydrazide, and H₄L³ = bis(2-hydroxy-3-methoxybenzylidene)adipohydrazide) were synthesized by direct reaction of [VO(acac)₂] with the hydrazone ligands. The ligands and complexes were characterized by FT–IR, UV–Vis, and NMR spectroscopic methods. The crystal structures of the complexes of L¹ and L³ were determined by X-ray analyses. The solid-state structure of the complex of L¹ features a 1D hydrogen-bonded chain from N⋯H–O hydrogen bonding. The catalytic activities of these complexes have been tested in the oxidation of various hydrocarbons using H₂O₂ as the terminal oxidant. Generally, good to excellent conversions have been obtained.     

Synthesis and crystal structure of bis(dimethylthioacetonedicarboxylate)nickel(II)

Summary The title compound has been synthesized and characterized. The crystal structure has been determined by single-crystal x-ray analysis from diffractometer data, and refined to R= 0.063 for 1889 observed reflections. Crystals are monoclinic, space group P2₁/n, witha=21.97(2),b=8.21(1),c=10.44(1) A, and =101.87(3), and Z=4. Both ligands are coordinated to nickel through sulphur and one oxygen atom to realize thecis form of the complex in the square planar coordination geometry. Bond distances are: Ni-S, 2.14(1), Ni-O, 1.87(1) and 1.90(1) Å. Each nickel atom also forms two close contacts with oxygen atoms from adjacent molecules.     

Reactions between 8-quinolinol (and related ligands) and triruthenium dodecacarbonyl; x-ray crystal structure determination of Ru3(CO)8(C9H6NO)2

8-Quinolinol reacts with Ru₃(CO)₁₂ to give Ru₃(CO)₈(C₉H₆NO)₂ and Ru- (CO)₂(C₉H₆NO)₂. A single-crystal X-ray study of the cluster compound shows that the three ruthenium atoms define an isosceles triangle, with two distances of 2.77 Å and one of 3.04 Å. Since both metalated oxygens act as three-electron donors (RuO distances 2.12 and 2.18 Å), the cluster is a fifty-electron species with a formal zero bond order for the elongated RuRu bond. Four other hydroxyhydrocarbylpyridine compounds also give complexes of composition Ru₃(CO)₈(L)₂ which probably have analogous structures.     

Synthesis, molecular, crystal and electronic structure of [(C6H6)RuCl(1,10-C12H8N2)]Cl

The [(C₆H₆)RuCl(1,10-C₁₂H₈N₂)]Cl complex has been prepared and studied by IR, UV-Vis, ¹H NMR spectroscopy and X-ray crystallography. The complex was prepared in reaction of [(C₆H₆)RuCl₂]₂ with 1,10-phenatroline in acetone. The electronic spectrum of the compound has been calculated using the TDDFT method.     

The crystal and molecular structure of 3,4-quinoxalino-1-telluracyclopentane C10H8N2TeII

The crystal and molecular structure of 3,4-quinoxalino-1-tellura(II)cyclopentane has been determined by X-ray diffraction at room temperature. The crystals are tetragonal, space group I4₁/a with a = b = 25.315(8), c = 6.010(1) Å and V = 3851.38 ų. The density of 1.96 g cm^?3 calculated on the basis of 16 molecules per unit cell is in agreement with the flotation value of 1.91 g cm^?3. The structure has been refined to a conventional R value of 0.0408 using 744 independent observed reflections obtained from four-circle diffractometer measurements. The structure consists of discrete molecules TeC = 2.134 Å (av.), CN = 1.343 Å (av.) and angle CTeC = 80.7° (e.s.d. 0.5) but the intermolecular TeTe bonds (3.791 and 3.998 Å) are less than the sum of the Van der Waals' radii thus indicating the presence of secondary bonding. These short intermolecular contacts in the crystal structure are consistent with the anomalous physical properties observed.     

Synthesis, structure and redox properties of bis(cyclopentadienyl)dithiolene complexes of molybdenum and tungsten

The compounds [Cp(2)M(S(2)C(2)(H)R)] (M = Mo or W; R = phenyl, pyridin-2-yl, pyridin-3-yl, pyridin-4-yl or quinoxalin-2-yl) and [Cp(2)Mo(S(2)C(2)(Me)(pyridin-2-yl)] have been prepared by a facile and general route for the synthesis of dithiolene complexes, viz. the reaction of [Cp(2)MCl(2)] (M = Mo or W) with the dithiolene pro-ligand generated by reacting the corresponding 4-(R)-1,3-dithiol-2-one with CsOH. These Mo compounds were reported previously (Hsu et al., Inorg. Chem. 1996, 35, 4743); however, the preparative method employed herein is more versatile and generates the compounds in good yield and all of the W compounds are new. Electrochemical investigations have shown that each compound undergoes a diffusion controlled one-electron oxidation (OX(I)) and a one-electron reduction (RED(I)) process; each redox change occurs at a more positive potential for a Mo compound than for its W counterpart. The mono-cations generated by chemical or electrochemical oxidation are stable and the structures of both components of the [Cp(2)Mo(S(2)C(2)(H)R)](+)/[Cp(2)Mo(S(2)C(2)(H)R)] (R = Ph or pyridin-3-yl) redox couples have been determined by X-ray crystallography. For each redox related pair, the changes in the Mo-S, S-C and C-C bond lengths of the {MoSCCS} moiety are generally consistent with OX(I) involving the loss of an electron from a π-orbital that is Mo-S and C-S antibonding and C-C bonding in character. These results have been interpreted successfully within the framework provided by DFT calculations accomplished for [Cp(2)M(S(2)C(2)(H)Ph)](n) (M = Mo or W; n = +1, 0 or -1). The HOMO of the neutral compounds is derived mainly from the dithiolene π(3) orbital (65%); therefore, OX(I) is essentially a dithiolene-based process. The similarity of the potentials for OX(I) (ca. 30 mV) for analogous Mo and W compounds is consistent with this interpretation and the EPR spectra of each of the Mo cations show that the unpaired electron is coupled to the dithiolene proton but relatively weakly to (95,97)Mo. The DFT calculations indicate that the unpaired electron is more localised on the metal in the mono-anions than in the mono-cations. In agreement with this, the EPR spectrum of each of the Mo-containing mono-anions manifests a larger (95,97)Mo coupling (A(iso)) than observed for the corresponding mono-cation and RED(I) for a W compound is significantly (ca. 300 mV) more negative than that of its Mo counterpart. [Cp(2)W(S(2)C(2)(H)(quinoxalin-2-yl))] is anomalous; RED(I) occurs at a potential ca. 230 mV more positive than expected from that of its Mo counterpart and the EPR spectrum of the mono-anion is typical of an organic radical. DFT calculations indicate that these properties arise because the electron is added to a quinoxalin-2-yl π-orbital.     

Synthesis and crystal structure of nickel(II) complexes with bis(5-methyl-2-thiophenemethyl)(2-pyridylmethyl)amine

A series of nickel(II) complexes having the (Me-Tp)₂PMA ligand ((Me-Tp)₂PMA = bis(5-methyl-2-thiophenemethyl)(2-pyridylmethyl)amine) with nitrates (1), chlorides (2), and perchlorates (3) as anions were synthesized and isolated. All these complexes were successfully characterized by physicochemical methods including X-ray crystallographic analysis. In complex 1, the ligand binds in a bidentate N₂ fashion, whereas in the cases of 2 and 3 the ligand binds in the tridentate N₂S form. The coordination geometry around the nickel(II) atoms in these complexes is distorted octahedral.     

Synthesis and crystal structure of cyclopentadienyl(1,4-dimethyl-1,4-dibora-2,5-cyclohexadiene)cobalt

The synthesis of the organometallic derivative cyclopentadienyl(1,4-dimethyl-1,4-diboracyclohexa-2,5-diene)cobalt is described. This complex, [(CH₃BC₄H₄BCH₃)Co(η-C₅H₅)], forms red-oranged monoclinic crystals, space group P2₁/a with Z = 4 in a unit cell of dimensions a 11.362(7), b, 7.467(7), c 13.290(12) Å, β 103.76(6)°. The structure has been elucidated by heavy-atom methods from 1732 reflections (I > 2σ(I)) measured on a Syntex P2₁ four-circle diffractometer and refined to R = 0.055. In the coordination complex all six atoms of the cyclohexadiene ring are within bonding distance of the metal atom, but the two boron atoms bend away from the metal atom, and the ring elongates slightly in the B---B direction. As a standard of comparison the known geometry of the free ligand [1,4-difluoro-1,4-dibora-2,3,5,6-tetramethylcyclohexa-2,5-diene] is used. The terminal methyl groups on the boron atoms, by contrast, bend slightly back towards the metal atom. The cyclopentadienyl ring remains planar but is positionally disordered.     

The electronic structure of bis(o-phenylenediamido)nickel,Ni[C6H4(NH)2]2

Extended Hückel and multiple scattering Xα calculations are reported for the title complex. Both sets of results are in quantitative agreement, suggesting that part of the unusual spectral and electrochemical properties of this system may be ascribed to the predominantly ligand character of the HOMO and LUMO orbitals.     

Synthesis,X-ray crystal structure and DFT studies of cobalt(II) and vanadium(V) complexes with N,N,O-tridentate aroyl-hydrazone based ligand

A new aroyl-hydrazone, 2-pyridine carboxaldehyde-derived hydrazone ligand and its cobalt(II) (1) and vanadium(V) (2) complexes were prepared. The structures of these compounds were investigated using elemental analysis, spectral (IR, UV), and X-ray diffraction measurements. The electrochemical properties of the complexes were studied by cyclic voltammetry. The hydrazone ligand acted as tridentate and coordinated to vanadium and cobalt via N-imine, N-pyridine, and O-benzohydrazide atoms. The Co(II) complex crystallizes in the monoclinic system, space group P2₁/c, and has a binuclear structure. Chloride ions behave as the linking bridge and a tridentate hydrazine ligand HL and water as the terminal capping ligands. The central Co(II) ion has distorted octahedral geometry. The vanadium(V) complex crystallizes in the monoclinic crystal system, space group P2₁/n, and can be described as having highly distorted trigonal-bipyramidal coordination. The geometries and electronic properties of the complexes were also obtained using DFT and TD-DFT calculations.