Ethoxo Groups Research Articles

Dinuclear Iron(III) and Nickel(II) Complexes Containing N-(2-Pyridylmethyl)-N'-(2-hydroxyethyl)ethylenediamine: Catalytic Oxidation and Magnetic Properties.

Dinuclear FeIII and NiII complexes, [(phenO)Fe(N3 )]2 (NO3 )2 (1) and [(phenOH)Ni(N3 )2 ]2 (2), were prepared by treating Fe(NO3 )3 ⋅9 H2 O and Ni(NO3 )2 ⋅6 H2 O in methanol, respectively, with phenOH (=N-(2-pyridylmethyl)-N'-(2-hydroxyethyl)ethylenediamine) and NaN3 ; both 1 and 2 were characterized by elemental analysis, IR spectroscopy, X-ray diffraction, and magnetic susceptibility measurements. Two ethoxo-bridged FeIII and two azido-bridged NiII were observed in 1 and 2, respectively; corresponding antiferromagnetic interaction via the bridged ethoxo groups and strong ferromagnetic coupling via the bridged end-on azido ligands within the dimeric unit were observed. Complex 1 did not exhibit any catalytic activity, while 2 exhibited excellent catalytic activities for the epoxidation of aliphatic, aromatic, and terminal olefins.

Oxovanadium(V) complexes incorporating tridentate aroylhydrazoneoximes: Synthesis, characterizations and antibacterial activity

Some new oxovanadium(V) complexes, [VOL 1–3(OEt)(EtOH)] ( 1– 3), have been reported, which were obtained from the reaction of the Schiff bases H 2L 1–3 (where H 2L 1 = the salicylhydrazone of diacetyl monoxime; H 2L 2 = the 4-methoxy salicylhydrazone of diacetyl monoxime and H 2L 3 = the 4-hydroxy salicylhydrazone of diacetyl monoxime) with VO(acac) 2 in a 1:1 molar ratio. Three 4-R-aroylhydrazoneoximes ( V) have been used as ligands in the present study, differing in the inductive effect of the substituent R (R = H, OCH 3 and OH), in order to observe their influence, if any, on the redox potentials and biological activity of the complexes. All the synthesized ligands and metal complexes were successfully characterized by elemental analysis, IR, UV–Vis and NMR spectroscopy. An X-ray diffraction study of [VOL 1(OEt)(EtOH)] ( 1) reveals that the metal center has a distorted octahedral O 5N coordination sphere, where the O,N,O donor ligand and the ethoxo group constitute a satisfactory O 3N basal plane. Cyclic voltammetry of the complexes show a quasi-reversible cyclic voltammetric response in the potential range 0.29–0.36 V involving a single electron V(V)–V(IV) reduction. The complexes have also been screened for their antibacterial activity against Escherichia coli, Bacillus, Proteus and Klebsiella. Minimum inhibitory concentrations of these complexes and the antibacterial activities indicate compound 1 as the potential lead molecule for drug design.

Mechanism of the catalytic gas-phase aldehyde production from trinuclear W 3S 4 complexes bearing W-OEt groups

Collision induced dissociation experiments of the alkoxo [W 3S 4(dmpe) 2(O)(OCH 2CH 3)] + tungsten (IV) cation reveal that aldehyde elimination is the dominant reaction pathway. Complementary deuterium labelling experiments give support to a hydrogen transfer mechanism, where the hydrogen atom exclusively originates from the α-position of the alkoxo ligand. On the basis of DFT calculations, two competitive mechanisms are proposed: one of them involving a proton transfer from the α-position of the alkoxo ligand to an oxygen atom of the vicinal W O group; the other corresponding to a hydride transfer mechanism from the α-position of the alkoxo ligand to the geminate tungsten center. The calculated energy profiles show that the former is thermodynamically favoured and the second is kinetically favoured, with small energy differences between the two reaction paths; in consequence, both mechanisms compete under our experimental conditions. The proton transfer mechanism occurs through a seven-membered transition state structure while hydride transfer takes place through a four-center structure defined by the metal and the oxygen, carbon and hydrogen atoms of the ethoxo group.

Synthesis and crystal structure of a mononuclear complex of oxorhenium (v) with 2,2′-dipyridylamine

The complex [ReOCl2(OEt)(dpa)] was prepared by reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of 2,2′-dipyridylamine (dpa) in ethanol under an inert atmosphere. Its X-ray crystal structure shows that the N,N-chelated dpa ligand is coordinated in the equatorial plane cis to the oxo and ethoxo groups, which are in trans positions relative to each other. The two pyridine rings of dpa are folded around the bridging nitrogen atom away from the oxo oxygen atom.

Synthesis and structure of cyclic hexanuclear oxo-alkoxo–carboxylatoniobium(IV) complexes

The synthesis and crystal structure of novel oxo-alkoxo–carboxylato Nb(IV) complexes, Nb 6(μ 2-O) 3(μ 2-O 2CCX 3) 6(μ 2-OC 2H 5) 6(OC 2H 5) 6 (X=Cl, F) are described. The single-crystal X-ray structure determination carried out, revealed a closed ring of six Nb(IV) ions linked alternately by two carboxylato groups and an oxo group, and two ethoxo groups. The hexanuclear molecule can essentially be described as a trimer of Nb 2(μ 2-OC 2H 5) 2(OC 2H 5) 2, each linked by an μ 2-oxo group and two μ 2-carboxylato groups. The ethoxo-bridged Nb–Nb distances are 2.735(5) Å, which is consistent with a single metal–metal bond, while the oxo- and carboxylato-bridged non-bonding Nb–Nb distances are 3.635(2) Å.

Synthesis, characterization and molecular structure of oxo and phenylimido rhenium(V) complexes of 1-phenyl-2-(diisopropylphosphino)-ethanone

New rhenium-oxo and phenylimido complexes were synthetized and isolated by reaction of 1-phenyl-2-(diisopropylphosphino)ethanone on ReOX 3(PPh 3) 2 (X=Cl, Br, I), ReO(OEt)Cl 2(PPh 3) 2 and Re(NPh)Cl 3(PPh 3) 2 in basic media (NEt 3). In these complexes the ligand bonds mainly as monoanionic enolato chelating agent. The reactions are solvent dependent. The disubstituted ReOX(PO) 2 compounds ( 1– 7) adopt a ‘twisted’ octahedral structure with a mixture of cis-PP and trans-PP configurations in toluene, thus indicating that in this case the stability gap between the two diastereoisomers is small. In ethanol, only the ‘twisted’ cis-PP conformers ReOCl(PO) 2( 1) and ReO(OEt)(PO) 2 ( 7) were observed. The ethoxo-oxo complex ReO(OEt)(PO) 2 ( 7) resulting from the stereoselective substitution of the halide by the ethoxo group is the unique species isolated when X=Br and I. The reaction with Re(NPh)Cl 3(PPh 3) 2 was less selective and, in ethanol, excess of ligand was needed to get trans-PP-Re(NPh)Cl(PO) 2 ( 8) as unique species. A mixture of ( 8), of the monosubstituted Re(NPh)Cl 2(PPh 3)(PO) ( 9) and of Re(NPh)Cl 2(PCO)(PO) ( 10) was observed in toluene with and without base. All these data emphasize the influence of the basicity and steric hindrance of the phosphinoenolato ligand on the rhenium complexes formation.

Tin dioxide thin films from Sn(IV) modified alkoxides — synthesis and structural characterization of Sn(OEt) 2(η 2-acac) 2 and Sn 4(μ 3-O) 2(μ 2-OEt) 4(OEt) 6(η 2-acac) 2

SnO 2 or doped SnO 2 thin films can be used as transparent conductors in various optoelectronic devices such as screens or solar cells. They usually present high optical transmittance, low resistivity and high chemical and mechanical stability. The synthesis and single crystal X-ray diffraction analysis of new tin (IV) modified alkoxides Sn(OEt) 2(η 2-acac) 2 ( 1) and Sn 4(μ 3-O) 2(μ 2-OEt) 4(OEt) 6(η 2-acac) 2 ( 2) (acacH=2,4 pentanedione) are reported. 1 crystallizes in the monoclinic system (space group P2 1/ n) while 2 crystallizes in the triclinic system (space group P1̄). The asymmetric unit of the molecular species Sn(OEt) 2(η 2-acac) 2 contains two monomers which are slightly different. Sn 4(μ 3-O) 2(μ 2-OEt) 4(OEt) 6(η 2-acac) 2 is a tetranuclear species in which Sn atoms are connected together by two triply bridging oxo ligands and four bridging ethoxo groups. Six terminal ethoxo groups and two chelating β-diketonato ligands are completing the coordination of the metal atoms. Their behaviour towards hydrolysis–condensation reactions is discussed.

Carboxylate Bridged Octaphenyltetra-antimony (V) ‘Cage’ Compounds; [(SbPh2)4(μ-O)4(μ-OH)2(μ-O2CR)2· HO2CR], where R = Me or t-Bu and the Crystal Structure of [(SbPh2)4(μ-O)4(μ-OH) (μ-OEt)(μ-O2CMe)2

Reactions of [SbPh2BrO]2 with carboxylates did not give [SbPh2(O2CR[2, the expected substitution products, which are highly sensitive to hydrolysis by traces of moisture, and cage compounds containing an Sb4O6 unit were obtained instead. With silver acetate and sodium trimethylacetate the products were [(SbPh2)4(μ-O)4(μ-OH)2(μ-O2CR)2]·HO2CR, R = Me 1 and R = t-Bu 2, respectively. An unusual compound, [(SbPh2)4(μ-O)4(μ-OH)(μ-OEt(μ-O2CMe)2] 3, in which one of the bridging hydroxo groups in 1 is replaced by an ethoxo group, was also isolated and its crystal structure determined.

Directed syntheses and structural studies of mononuclear copper(II) and heterodinuclear copper(II)–iron(III) complexes from the same unsymmetrical dinucleating ligand ‡

Mononuclear copper(II) [Cu(H3L)(O2CMe)]BPh41 and heterodinuclear copper(II)–iron(III) [FeCuL(µOEt)]ClO42 complexes from the same dinucleating ligand H3L have been prepared and isolated {H3L = 2-[bis(2-hydroxybenzyl)aminomethyl]-4-methyl-6-[bis(2-pyridylmethyl)aminomethyl]phenol}. The crystal structure of the mononuclear complex 1 demonstrated the site-directed complexation with H3L. For the heterodinuclear complex 2 the crystal structure reveals that the copper and iron atoms are bridged by the central phenoxo moiety and by an exogenous ethoxo group. In addition this structure showed that the iron atom is five-co-ordinated. Temperature-dependent magnetic susceptibility measurements revealed an antiferromagnetic interaction (ca.J = –58.1 cm–1) between the copper and iron atoms in 2. Cyclic voltammograms in dichloromethane vs. Ag–AgNO3 revealed a quasi-reversible redox behaviour for CuII–CuI in 1 and 2 (E½ = –0.77 and –0.74 V respectively). The reduction of FeIII in 2 is irreversible with Epc = –1.69 V. The CuIFeIII complex is thermodynamically stable towards comproportionation.

Structural and magnetic characterisation of the compound [NEt4][Cr2(EtO)3{H2B(pz)2}2(NCS)2](pz = 1-pyrazolyl), a binuclear complex of chromium(III) with three bridging ethoxo groups

The crystal and molecular structure of [NEt4][Cr2(EtO)3{H2B(pz)2}2(NCS)2][H2B(pz)2= dihydro-bis(1-pyrazolyl)borate] has been determined by single-crystal X-ray diffraction methods. The crystals are monoclinic, space group P21, with a= 9.561(9), b= 15.826(4), c= 12.979(3)A, β= 93.06(8)° and Z= 2. The complex anion consists of two chromium(III) ions in chemically identical and approximately octahedral environments. The metal ions are bridged by three ethoxo groups. The co-ordination around each metal is completed by two N atoms of a H2B(pz)2 ligand and by the N atom of a NCS anion. The temperature dependence of the magnetic susceptibility of the compound has been determined in the range 8–280 K. The exchange interaction between the two chromium(III) ions was found to be antiferromagnetic with J= 87.0(2) cm–1 and the exchange Hamiltonian is H=JS1·S2.

The versatility of the dihydrogenobis(1-pyrazolyl)borate ligand, H2B(pz)2–: novel anionic complexes with chromium(II), chromium(III), and manganese(II). X-Ray structure of [AsPh4][MnCl{H2B(pz)2}2

New five-co-ordinate chromium(II) and manganese(II) complexes with the ligand dihydrogenobis(1-pyrazolyl)borate, H2B(pz)2, have been prepared and characterized. The complexes have the general formula A[MX{H2B(pz)2}2](M = CrII or MnII; A = NEt4, PPh4, or AsPh4; X = halides or pseudohalides). All of the complexes are high spin. The structure of [AsPh4][MnCl-{H2B(pz)2}2] has been determined by single-crystal X-ray diffraction methods. The compound crystallizes in the space group P21/n with a= 16.952(4), b= 13.039(3), c= 17.331(4)A, β= 105.53(2)°, and Z= 4. The structure was solved by heavy-atom methods and refined to R= 0.058. The co-ordination geometry about manganese(II) is square pyramidal with the four donor N atoms of the two H2B(pz)2 ligands forming the basal plane and the Cl atom occupying the apical position. The Mn atom is displaced by 0.52 A from the base of the pyramid toward the Cl atom. Slow oxidation of [NEt4][Cr{H2B(pz)2}2(NCS)] in solution yields the chromium(III) complex [NEt4][Cr2(EtO)3{H2B(pz)2}2(NCS)2] with co-ordinated ethoxo groups.

Rhenium(V) oxide complexes. Crystal and molecular structures of the compounds trans-ReI 2O(OR)(PPh 3) 2 (R = Et, Me) and of their hydrolysis derivative ReIO 2(PPh 3) 2

The structure of the complex ReI 2O(OEt)(PPh 3) 2·3/2C 6H 6 (I) has been investigated: the dark-yellow crystals are monoclinic, space group P2 1/ n, with a = 17.410(8), b = 17.322(6), c = 15.039(5) Å, β = 103.49(3)°, Z = 4. Least-squares refinements based on 3636 significant counter data led to a final R value of 0.059. The compound exhibits a slightly distorted octahedral coordination, with the two PPh 3 groups trans between themselves (mean ReP 2.523 Å), as well as the two iodide ligands (mean ReI 2.789 Å). The ethoxo group (ReO 1.880(9) Å) and the oxide ligand (ReO 1.715(9) Å) occupy the other two coordination sites. Compound I in methanol transforms into ReI 2O(OMe)(PPh 3) 2 (II), which has been characterized by X-ray analysis in crystals containing CHCl 3 molecules of solvation. The crystals are triclinic, space group P 1 , a = 12.835(3), b = 13.067(4), c = 13.485(4) Å, α = 89.71(2)°, β = 71.61(2)°, γ = 70.19(2)°, Z = 2. The refinements gave a final R value of 0.036, on the basis of 4524 significant counter intensities. The stereochemistry and the bond parameters are similar to those found in compound I. In particular the ReO (methoxo) and ReO (oxide) bond lengths are 1.859(5) and 1.698(5) Å respectively. Hydrolysis reactions of both compounds I and II give the violet derivative ReIO 2(PPh 3) 2 (III). The crystal data are: orthorhombic, space group Aba2, a = 19.834(5), b = 16.144(3), c = 10.560(2) Å, Z = 4. 1435 significant counter reflections were used in the refinements the final R value being 0.039. The compound is an unusual example of a five coordinate Re(V) complex. It possesses a rigorous C 2 crystallographic symmetry and exhibits a distorted trigonal bipyramidal stereochemistry, with the two PPh 3 groups in an axial direction (ReP 2.488(3) Å) and the two oxide and the iodide ligands in equatorial positions. The ReI and ReO interactions have values of 2.664(2) and 1.742(11) Å respectively.