Dioxime Ligand Research Articles

Organocobaloximes with mixed dioxime equatorial ligands: a convenient one-pot synthesis. X-ray crystal structures of BnCo III(dmgH)(dpgH)Py and BnCO III(chgH)(dpgH)py

A simple and general route to the synthesis of organocobaloxime with mixed dioxime ligands, RCo(dmgH)(dpgH)Py and RCo(chgH)(dpgH)Py, has been described. The 13C-NMR chemical shifts have been analysed to see whether one dioxime wing has any effect on the other dioxime wing. The first crystal structure of an organocobaloxime with mixed dioxime ligand in the same complex, BnCo(dmgH)(dpgH)Py and BnCo(chgH)(dpgH)Py, is reported.

Chemistry of ruthenium with some dioxime ligands. Syntheses, structures and reactivities

Reaction of two dioxime ligands, viz. dimethylglyoxime (H 2dmg) and diphenylglyoxime (H 2dpg), (abbreviated in general as H 2L, where H stands for the oxime protons) with [Ru(PPh 3) 3Cl 2] in 1:1 mole ratio affords complexes of type [Ru(PPh 3) 2(H 2L)Cl 2]. Structure of the [Ru(PPh 3) 2(H 2dpg)Cl 2] complex has been solved by X-ray crystallography. The coordination sphere around ruthenium is N 2P 2Cl 2 with the two PPh 3 ligands in trans and the two chlorides in cis positions. Reaction of the dioxime ligands with [Ru(PPh 3) 3Cl 2] in 2:1 mole ratio in the presence of a base affords complexes of type [Ru(PPh 3) 2(HL) 2]. Structure of the [Ru(PPh 3) 2(Hdmg) 2] complex has been solved by X-ray crystallography. The coordination sphere around ruthenium is N 4P 2 with the two PPh 3 ligands in trans positions. Reaction of the [Ru(PPh 3) 2(H 2dpg)Cl 2] complex with a group of bidentate acidic ligands, viz. picolinic acid (Hpic), quinolin-8-ol (Hq) and 1-nitroso-2-naphthol (Hnn), (abbreviated in general as HL′, where H stands for the acidic proton) in the presence of a base affords complexes of type [Ru(PPh 3) 2(H 2dpg)(L′)] + isolated as perchlorate salts. All the complexes are diamagnetic (low-spin d 6, S=0) and in dichloromethane solution show several intense MLCT transitions in the visible region. Cyclic voltammetry on all the complexes shows a reversible ruthenium(II)–ruthenium(III) oxidation within 0.36–0.98 V versus SCE followed by a quasi-reversible ruthenium(III)–ruthenium(IV) oxidation within 0.94–1.60 V versus SCE.

A novel tetraoxime and its dinuclear and tetranuclear transition metal complexes

A new bis(dioxime) ligand (H4L) containing the diphenyl ether moiety has been prepared by reacting 3,3′,4,4′-tetraaminodiphenyl ether (1) with 2,3-butanedione monoxime (2). Dinuclear copper(II) and cobalt(III) complexes of H4L exhibit a metal–ligand ratio of 2:1 and the ligand coordinates through the 4 nitrogen atoms, as do most bis(dioximes). The [Cu2(H2L)](ClO4)2 molecule coordinates to the other two copper(II) ions through the deprotonated oximate oxygens to yield a tetranuclear structure, doubly-bridged by the oximate groups in a cis arrangement. The structure of bis(dioxime) and its complexes were identified by elemental analyses, 1H-, 13C-n.m.r, i.r and m.s. spectral data.

Aquabis(2,3-butanedione dioximato-N,N')(cyclopentyl)cobalt(III)

The crystal structure determination of the title compound, a model for coenzyme B12, indicates that it is [Co(C4H6N2O2)(C5H9)(C4H8N2O2)(H2O)], i.e. one 2,3-butanedione dioxime ligand is neutral and the second is a dianion, with the CoIII ion in a distorted octahedral environment. The axial Co—C bond length [2.029 (2) A] is close to that of coenzyme B12[2.00 (1) A].

Organocobaloximes: synthesis, oxygen insertion and kinetics

A total of 27 organocobaloximes have been synthesised and characterized with three different dioxime ligands, dmgH, chgH and dpgH. Many of the chgH and all the dpgH complexes have been synthesised for the first time. The insertion of molecular oxygen into these organocobaloximes, RCoIII(L2)B [L=dmgH, chgH and dpgH) under thermal and photochemical conditions have been studied. Kinetic studies at ambient temperature under irradiation show that the rate of insertion depends upon the nature of R, L, B and the solvent. The rate follows the order dpgH>chgH>dmgH; Naphthyl>heteroaromaticmethyl>benzyl; piperidine>morpholine>γ-picoline>pyridine>2-bromopyridine>2-acetylpyridine; and the rates are faster in acetonitrile than in acetone and chloroform. In methanol, the benzylic cobaloximes exist as an equilibrium mixture of solvated penta-coordinated and hexa-coordinated species and in chloroform these exist as hexa-coordinated species.

Synthesis, structures and magnetochemistry of binuclear cobalt(II), nickel(II) and copper(II) complexes of 2,6-diformyl-4-methylphenol dioxime

Reaction of 2,6-diformyl- and 2,6-diacetyl-4-methylphenol with a large excess of both NH2OH·HCl and CH3CO2K in EtOH affords high yields of 2,6-diformyl-4-methylphenol dioxime (2-hydroxy-5-methylbenzenedicarbaldehyde dioxime) (H3L1) and 2,6-diacetyl-4-methylphenol dioxime (H3L2), respectively. The crystal structure of (H3L2) shows intramolecular hydrogen bonding with long-range intermolecular π-stacking interactions and an extended intermolecular hydrogen-bonding network. The binuclear complexes of CoII, NiII and CuII—[Co2(H2L1)2(MeOH)2(H2O)2]Cl2·2MeOH, [Ni2(H2L1)2(H2O)4][ClO4]2·2H2O and [Cu2(H2L1)2(ClO4)2], respectively—derived from the dioxime ligand (H3L1) have been synthesized and characterised and their single-crystal structures determined. The structure of [Co2(H2L1)2(MeOH)2(H2O)2]2+ shows each high-spin CoII to be six-co-ordinate and bound to an N2O4-donor array presented by two dioxime ligands and axially co-ordinated H2O and MeOH molecules, the dioxime ligands co-ordinating via the imino N- and phenoxy O-donors. The structure of [Ni2(H2L1)2(H2O)4]2+ shows two octahedrally co-ordinated NiII each with an N2O4 donor set similar to that in [Co2(H2L1)2(MeOH)2(H2O)2]2+ except that the co-ordination sphere of each NiII is completed by axial ligation to two H2O molecules. The structure of [Cu2(H2L1)2(ClO4)2] confirms N2O4 donation at CuII with two bidentate ClO4– anions, Cu· · ·O 2.51(2), 2.76(2) Å, interacting with the metal centres on either side of the planar oxime–phenolate array. In all three complexes the two dioxime ligands are monodeprotonated at the phenolic oxygen, and the oximes are linked by hydrogen bonds, which results in a pseudo-macrocyclic framework. Magnetic susceptibility measurements on the complexes over the range 2.5–340 K confirm that the complexes are antiferromagnetically coupled with values for the magnetic exchange constant J of –6.9 ± 0.1, –16.0 ± 0.6, and –452 ± 4 cm–1 for [Co2(H2L1)2(MeOH)2(H2O)2]Cl2, [Ni2(H2L1)2(H2O)4][ClO4]2 and [Cu2(H2L1)2(ClO4)2], respectively.

A study of cis influence in alkyl cobaloximes

Abstract Thirty-nine alkylcobaloximes have been synthesized (many of them new) and characterized with three different dioxime ligands, dmgH, dpgH and chgH. The chgH cobaloximes have been synthesized for the first time from ClCo(chgH)2Py complexes. A rapid purification procedure using column chromatography affording analytically pure products has been established for all the three series of cobaloximes. Methanol has been found to be the best solvent for the study of cobalt-carbon charge transfer (Co-C CT) band as the alkylcobaloximes exhibit a prominent maxima in this solvent. For MeCo(dpgH)2Py the Co-C CT band is not resolved; a λmax value of 453.6 nm is proposed for it. The literature value of 473 nm is doubtful. The variation of λmax values with increasing alkyl chain length is surprisingly similar for all the three series of cobaloximes. 13C-Spectroscopy has revealed that the Pα experiences the most cis influence and Pβ the least. The cis influencing ability of the chgH ligands have been found to be negligible (as compared to dpgH) on the alkyl chain as well as on the Pβ and Pγ carbons. 1H-NMR studies indicate that the cis influence is felt most by the cobalt bound methylene protons followed by Pα and Pβ. Interestingly, the O-H-O resonance for the chgH cobaloximes appear ∼0.5 ppm upfield than the analogous dmgH complexes in all the thirteen alkylcobaloximes. The order of cis influencing ability has been found to be dpgH > chgH > dmgH by all the three spectroscopic techniques. This sequence is exactly the reverse order of the corresponding Co(I) nucleophilicities. C=N and N-O stretching frequencies in the IR studies for three series of cobaloximes follow the order dmgH > chgH > dpgH. The order can be explained if one invokes the electronic effect of the substituents on the dioximic moiety.

Bis(didentate) open-chain and tetradentate pseudo-macrocyclic bridging co-ordination modes of N,N′ -bis(1,3-dimethyl-5-nitroso-2,4-dioxopyrimidin-6-yl)butane-1,4-diamine

E. Colacio, J. M. Domínguez-Vera, A. Escuer, R. Kivekäs, M. Klinga, J. Moreno and A. Romerosa, J. Chem. Soc., Dalton Trans., 1997, 1685 DOI: 10.1039/A607956C

Cobalt(III) complexes of 2-oximino-10-oximino-3,9-dimethyl-4,8-diazaundeca-3,8-diene

The pseudo-macrocyclic dioxime ligand [(1) = LH] has been synthesized. A variety of cobalt(III) complexes, trans-[CoLX2], have been prepared and characterized (X = Cl, Br, NO2, NCS or N3) and [CoLCl(NO2)]. Vis. and i.r. spectra of the complexes are reported and aspects of the solution chemistry of the complexes studied.

Synthesis and Characterization of Mono‐ and Trinuclear Complexes of BF2+ Bridged Macrocycles

AbstractDibenzo[e,k]‐2,3‐bis(hydroxyimino)‐1,4‐dithia‐7,10‐diaza‐2,3,8,9‐tetrahydrocyclododecine (H2L) has been prepared from 1,2‐bis(o‐mercaptoanilino) ethane (4) and (E,E)‐dichloroglyoxime. A mononuclear complex with a metal: ligand ratio of 1:2 has been isolated for cobalt(III). The CoIII complex of H2L has been prepared with L′ = 2,6‐lutidine, and with a chlorine ion as axial ligands. In addition to that, the synthesis of a new cobalt complex which contains BF2+ bridges is achieved with the bis(E,E)‐dioxime ligand. The trinuclear complex of this CoIII complex has been obtained by the reaction of BF2+ bridged CoIII complex with Pd[bis(benzonitrile)]Cl2. The structures of these complexes and (E,E)‐dioxime were identified by using elemental analysis, 1H and 13C‐NMR, IR and MS spectral data.

Synthesis of Two Newvic-Dioxime Ligands Containing Azo Group and Their Complexes with Ni(II) and Cu(II)

Abstract Two vic-dioxime ligands were synthesised by reacting anti-dichloroglyoxime with 4-aminoazobenzene and 2′, 3-dimethyl-4-aminoazobenzene, respectively, and then their nickel(II) and copper(II) complexes were synthesised. The ligands and complexes were characterised by elemental analyses, magnetic susceptibility measurements and ′H nmr, infrared, UV-visible and atomic absorbtion spectroscopy.

Kinetic and solvatochromic behaviour of low-spin iron(II) complexes of pyridineoximate and dioximate ligands

Kinetic results are presented for dissociation (aquation) of low-spin tris-diimine-iron(II) complexes derived from 2-pyridinealdoxime, 2-acetylpyridineketoxime and 2-benzoylpyridineketoxime in acidic aqueous and mixed aqueous media. The preparation and solvatochromic behaviour are described for ternary bis-diimine-dicyano-iron(II) complexes derived from 2-acetylpyridineketoxime and from four dioximes. These results are considered in relation to hydration and (selective) solvation of these ligands and their complexes.

An unexpected by-product obtained during the preparation of technetium(III) boronic acid adducts of dioximes. The single crystal structure of TcCl(DMG) 2(BDI)BEt (DMG=dimethylglyoxime, BDI=butane-2, 3-dione imine-oxime)

An unusual Tc(III) boron-capped imine-oxime complex has been isolated from the reaction of 99TcCl 3(CH 3CN)(PPh 3) 2, dimethyl glyoxime (DMG) and ethyl boronic acid (EtB(OH) 2). A single crystal X-ray structure analysis of this molecule 99TcCl(DMG) 2(BDI)BEt (BDI=butane-2, 3-dione imine-oxime) shows it to be seven coordinate: TcClC 14H 25N 6O 5B, a=9.073(2), b=23.686(5), c=19.539(6) Å; β=93.77(2)°, P2 1/ n, Z=8. Its structure is very similar to that of previously reported Tc(III) complexes 99TcCl(dioxime) 3BR, except that one dioxime ligand on the molecule has been reduced to an imineoxime.

Synthesis and Complexation of 1,2‐Bis[(monoaza[15]crown‐5)‐N‐yl]glyoxime. Crystal Structure of (1,2‐Bis[(monoaza[15]crown‐5)‐N‐yl]glyoximato)palladium(II)

AbstractA new vicinal dioxime ligand with two crown‐ether groups, 1,2‐bis[(monoaza[15]crown‐5)‐N‐Yl]‐glyoxime(LH2), has been prepared from cyanogen di‐N‐oxide and monoaza[15]crown‐5. Ni(II), Pd(II), and Pt(IV) complexes of LH2 with or without alkali‐metal ions bound to macrocyclic groups have been isolated. The high affinity of [Pd(LH)2] and [Ni(LH)2] for the K+ ion is observed in solvent extraction experiments. A single‐crystal X‐ray structure confirms the postulated geometry of [Pd(LH)2]‐ The Pd‐atom of the centro‐symmetric molecule has square‐planar PdN4 coordination where Pd–N distances range from 1.978(3) to 1.970(3) Å. The N–Pd–N intraligand angle is 79.9(1)°.

ChemInform Abstract: vic‐Dioximate Complexes of Silver(III).

AbstractThe bis‐chelate complexes (I) of Ag(III) are prepared by direct mixing (Ag(OH)4)‐ and the dioxime ligands in alkaline solutions and characterized by UV/VIS spectra.

Electron transfer between bis(dimethylglyoxime)copper(II) and diglycylethylenediamine copper(III). Stabilization of copper(III) by a dioxime ligand

Bis(dimethylglyoxime)copper(II), Cu II(DMGH) 2, is readily oxidized to the corresponding copper(III) complex. Cyclic voltammetry exhibited quasi-reversible one-electron transfer with peak-to-peak separation of ≈ 80 mV. The E 1/2 value varied linearly with −log[H +] with a slope of −59 mV, showing the involvement of one proton in the electrode reaction. The kinetics of the oxidation of Cu II(DMGH) 2 by Cu III(H −2DGEN) + (DGEN = diglycylethylenediamine) showed a first-order dependence on both the reductant and the oxidant. The second-order rate constant, k 2, varies with [H +] according to: k 2 = k ′ 2 + k 3 / [ H + ] . The mechanism of electron transfer is discussed in terms of inner- and outer-sphere mechanisms.

Preparation and characterization of ruthenium(II) clathrochelate complexes

Synthetic routes were developed for the preparation of clathrochelate complexes of ruthenium(II) utilizing a totally encapsulating ligand derived from dioxime ligands (1,2-cyclohexanedione dioxime, diphenylglyoxime and dimethylglyoxime) and various boron capping agents (boronic acids, borate esters, and boron halides). These complexes were fully characterized by 1H NMR, U'V-vis and IR spectroscopies. Cyclic voltammetric electrochemical experiments were performed and indicate that the stability of a ruthenium(III) clathrochelate complex is dependent on the nature of the substituent attached to the boron cap. Specifically, the stability increases with the length of the linear chain alkoxy groups attached to boron, and decreases for bulky alkoxy groups.

An XPS investigation on a series of schiff base dioxime ligands and cobalt complexes

X-ray photoelectron Spectroscopy (XPS) spectra of a series of multidentate dioxime Schiff bases and their cobalt (II) and cobalt (III) complexes have been recorded. The basis for the measurements and calibrations was the mean C1 s binding energy of a phenyl group of the ligands. In this way all calibrations were related to the level of a previous standard which was based on IR intensity measurements of the C-H stretching vibration of the phenyl group. From the thus well-calibrated binding energies of nitrogen, cobalt and halides the effective charges have been estimated by using previously established relations between binding energies and charge. It is shown that the sum of the increase in charge of the inner sphere ligating atoms corresponds very neatly to the decrease in charge of the cobalt atom. Quantitatively the charges agree very well with typical calculations reported from quantum chemical estimates; e.g. the charge on amino nitrogens in the Co II and Co III complexes is q n = −0.25±0.03. Measurements were also made, in relevant cases, using the Cl2 p 3 2 or N1s binding energy value in ClO 4 − and NO 3 −, respectively, as reference. As these anions have previously been characterized, also using phenyl C1s (calibrated by IR intensity measurements) as internal standard, it is instructive that the binding energies agree very well with those determined by using the phenyl group in a more direct way.

Synthesis and spectroscopic studies of dioxouranium (VI) complexes derived from some oximes and containing dihydroxo bridges

The reaction between uranyl acetate dihydrate and some mono- and dioxime ligands in absolute ethanol and in the presence and/or absence of sodium acetate is reported. The structures of the isolated dioxouranium (VI) complexes as well as the existence of dihydroxo bridge structures are characterized by elemental analyses, molar conductivities, pH, spectra (i.r., u.v., NMR) and magnetic measurements. Molecular weight measurements suggest a dimeric structure for all complexes except that derived from p-dimethylaminobenzaldehyde-oxime in the presence of sodium acetate. Infrared spectral data show that the oximes behave as mononegative monodentate ligands with displacement of a hydrogen atom from an NOH group. Also, the spectral data indicate that the acetate group behaves as a mono- or bidentate ligand. Moreover, the existence of a dihydroxo bridge is confirmed. Finally, simple mechanisms, in solution and/or solid, are proposed for the reactions between ligands containing attracting and/or donor groups and uranyl acetate dihydrate.

Synthetic conducting materials. I. Partial oxidation of bis(difluoroboron-diphenylglyoximato)nickel(II) with iodine

Bis(difluoroborondiphenylglyoximato) nickel(II), Ni(DPGB) 2, has been synthesized which used a dioxime ligand entailing BF 2 bridge. This complex was further oxidized by iodine to form partially oxidized crystal with metallic luster. The compound Ni(DPGB) 2I 3.93 has been shown by single-crystal X-ray diffraction to crystallize in monoclinic space group I 2/c with eight formula unit in a cell of dimensions a=21.812(5) A ̊ and b=13.883(5) A ̊ , c=23.612(6) A ̊ . Full-matrix least-squares refinement gave a final value of R 1=0.1178 for 1360 reflections. The crystal structure consists of slipped stacked Ni(DPGB) 2 units, each eclipsed with respect to its nearst neighbors, and disordered zig-zag chains of iodine atoms extending in the c-direction. Resonance Raman studies indicate that the predominant form of the iodine present is I 2·I 3 −. (fundamental transition ν=177 cm −1 vs and ν=108 cm −1 w). Thus, the Ni(DPGB) 2 unit is formally in fractional oxidation state of +0.78(6). the partial oxidation of Ni(DPGB) 2 was also evidenced by the infrared and mass spectrometry. Thermogram of this compound show a very small endothermic peak as weight change 35.36% which is due to the iodine loss. This shows the iodine is not chemically bonded on the nickel complex. After the iodine was removed, a new compound has a structure with an axial coordinated iodide was proposed. Powder electrical conductivity is 4.4×10 −5 Ω −1cm −1 at 25°C. Variable-temperature studies show the conductivity to be thermally activated, with activation energy of 0.48 eV.