Oxamide Ligand Research Articles

Dinuclear Nickel(II) Complex of a Novel Oxamido Ligand as a Chelating Agent

The dinuclear nickel(II) complex of an oxamide ligand reacted as a chelating ligand with transition metal cations to yield either tetra- or polymetallic complexes. The parent oxamido ligand is decadentate hexabasic and contains two symmetrical sets of N2O3 coordinating sites. The inner N2O3 sites of each set are coordinated to a nickel(II) cation. The outer O2O sites are available to coordinate to other metal cations. The reactions of the parent complex [(H2L)Ni2].EtOH with Ni(II), Co(II), Mn(II), UO2(VI) and Fe(III) cations yielded the following products: [LNi2M2Cl2(OH2)4], M = Ni(II) or Mn(II), [(HL)Ni2CoCl(OH2)2]n, [LNi2UO2(MeOH)]n and [LNi2Fe3Cl7(OH2)2]2. The products were characterized by elemental analyses, IR, UV-Visible and mass spectra. In addition the values of their magnetic moments indicated antiferromagnetic interactions between neighbouring metal cations. The magnetic exchange takes place via the oxamido linkage and either the chlorine and/or oxygen bridges. Referee I: T. C. Strekas Referee II: L. J. Boucher

Syntheses, structure and magnetic properties of dinuclear oxamidato-bridged copper(II) complexes

A new N,N′-disubstituted oxamide ligand H 4OBO which represents N,N′-bis (2-hydroxybenzyl)oxamide, related monomeric copper(II) complex salt Na 2[Cu(OBO)]· H 2O and two oxamidato-bridged dinuclear copper(II) complexes, namely [Cu 2(OBO) (bipy)]·2H 2O ( 1), [Cu 2(OBO)(py) 4] ( 2) (bipy = 2,2′-bipyridine, py = pyridine) have been synthesized. Single crystal X-ray analysis revealed that the complex 2 has a trans-oxamidato-bridged dinuclear copper(II) structure, in which each copper(II) ion exhibits a distorted square-pyramidal surrounding. Complex 2 is rapidly turned into a complex [Cu 2(OBO)(py) 3(H 2O) 2] ( 3) when exposed to the air. Based on the spin Hamiltonian H = −2 JS A · S B, the magnetic susceptibility data of 1 and 3 have been best fitted with J values of 209 and 161 cm −1, respectively.

Conformational change of the N,N′-bis(3-aminopropyl)oxamidate ligand in nuclearity tailoring copper(II) complexes

N,N′-Bis(3-aminopropyl)oxamide (H2L1) which can adopt cis and trans conformations reacted with copper(II) salts in its deprotonated form to yield the compounds [CuL1]1, [Cu3L21(NO3)2]·H2O 2, [Cu2L1(NO3)2]3 and [Cu2L1(O2CMe)2]·2H2O 4. The structures of 1, 3 and 4 have been determined by single-crystal X-ray diffraction methods. That of 1 consists of mononuclear [CuL1] units where the oxamidate is in a cis conformation co-ordinated to the copper atom through its four nitrogen atoms. The copper surroundings are close to square planar. The amidate–copper bond distance [1.955(6)Å] is significantly shorter than that involving the amine group [1.999(7)Å]. The structures of 3 and 4 comprise centrosymmetric trans oxamidate-bridged copper(II) dinuclear units which are linked by asymmetric bis(monodenate) nitrate (3) and acetate (4) ligands to yield a sheet-like polymer (3) and an alternating chain (4). The co-ordination geometry around each copper atom is distorted square pyramidal: the equatorial plane comprises the oxygen and nitrogen atoms of the amide, the nitrogen atom of the amine group and an oxygen atom from nitrate (3) or acetate (4) ligands. The apical position is filled by an oxygen atom from another nitrate (3) or acetate (4) group. The copper–copper separations across the oxamidate are 5.190(1) and 5.244(1)Å for 3 and 4, respectively, and those across the nitrato and acetato groups are 5.116(1) and 3.350(1)Å. Variable-temperature magnetic susceptibility measurements show a Curie law behaviour for 1 and the occurrence of a strong antiferromagnetic coupling through the oxamidate bridge in 2–4(J=–325, –393 and –305 cm–1, respectively). The versatility of L1 as a ligand and its ability to mediate strong antiferromagnetic interactions is analysed and discussed.

An alternating copper(II) chain with bridging azide and oxamidate ligands: crystal structure and magnetic properties of [Cu2(dmaeoxd)(N3)2(H2O)2] and [{Cu2(dmaeoxd)(N3)2}N]{H2dmaeoxd =N,N′-bis[2-(dimethylamino)ethyl]oxamide}

Two new azide-containing complexes [Cu2(dmaeoxd)(N3)2(H2O)2]1 and [{Cu2(dmaeoxd)(N3)2}n]2{H2dmaeoxd =N,N′-bis[2-(dimethylamino)ethyl]oxamide} have been synthesized and characterized by single-crystal X-ray diffraction methods: 1, triclinic, space group P= 8.620(3), b= 9.824(3), c= 11.216(3)A, α= 85.56(3), β= 86.90(3), γ= 89.98(3)° and Z= 2; 2, monoclinic, space group P21/n, a= 9.1 85(1), b= 11.477(4), c= 7.917(3)A, β= 100.88(3)° and Z= 2. The structure of 1 is made up of two neutral centrosymmetric trans oxamidate-bridged copper(II) dinuclear units with unidentate azide ligands and weakly co-ordinated water molecules. Each copper atom has a distorted square-pyramidal geometry with an oxygen and two nitrogen atoms from the oxamidate group and one nitrogen atom from the azide group forming the equatorial plane and one oxygen atom from water at the axial position. The structure of 2 consists of neutral chains of copper(II) with an alternating azide–oxamidate bridging arrangement. The oxamidate group acts as a bis(terdentate) ligand as in 1 and the azide bridges the metal atoms in an asymmetrical end-on fashion. Each copper atom has a distorted square-pyramidal geometry with one oxygen and two nitrogen atoms from the oxamidate ligand and one nitrogen atom from the azide group in the equatorial plane, whereas the axial position is occupied by a nitrogen atom of another azide group. The metal–metal separation through the oxamidate in each compound is very similar [5.202(1) and 5.232(1) in 1 and 5.286(1)A in 2] and much larger than that through azide in 2[3.395(1)A]. An investigation of the magnetic properties of 1 and 2 in the temperature range 80–300 K revealed the occurrence of strong antiferromagnetic interactions through oxamidate in both compounds and a weaker ferromagnetic coupling through the end-on azide bridge in 2.

Oxamidato complexes. Part 4. Electrochemical study of the copper(III)/copper(II) couple in monomeric N,N?-bis(substituent)oxamidatocopper(II) complexes

The electrochemical behaviour of a series of monomeric N,N′-bis(substituent)oxamidato copper(II) complexes of formula Na2[Cu(3,5,3′,5′-X4obbz)]·4H2O [X = Cl (1), Br (2), I (3) and obbz = oxamidobis(benzoato)], Na2-[Cu(obbz)]·4H2O (4), Na2[Cu(5,5′-Me2obbz)]·4H2O (5), Na2[Cu(4,5,4,5′-(MeO)4obbz)]·4H2O(6),Na2[Cu(obp)]· 3.5H2O (7) (obp = oxamidobis(propionato)) and Na2[Cu(pba)]·6H2O (8), [pba = propylenebis(oxamate)] has been investigated by cyclic voltammetry, rotating disk electrode and coulometry in water and dimethylsulphoxide (dmso) solutions. NaNO3 (0.1 M) and n-Bu4NPF6 (0.1 M) were used as supporting electrolytes in H2O and dmso respectively, all solutions being thermostatted at 25 °C. In aqueous solution, the complexes show an oxidation peak ranging from 1.19 to 0.86 V (values referred to the s.c.e.), the corresponding reduction being unobserved, even at high scan rates. In dmso, all the complexes exhibit only one oxidation peak ranging from 0.86 to 0.51 V, the corresponding reduction being observed for all of them except for (3). The oxidation potentials are strongly dependent upon the nature of the N,N′-substituent of the oxamide. The copper(III)-assisted hydrolysis of the oxamidate ligand is analysed in terms of the lack of planarity of the oxamidate ligand induced by the steric effect of the halogen substituent in the 3-position on the phenyl rings. The influence of the nature of the solvent was also studied.

Magnetic properties and crystal structure of a linear-chain copper(II) compound with bridging chloride and oxamidate ligands

The compound [Cu2(L)Cl2][H2L =N,N′-bis(3-amino-2,2-dimethylpropyl)oxamide] has been prepared and characterized by means of structural and magnetic measurements. The crystals are triclinic, space group P, with a= 6.630(1), b= 7.443(1), c= 9.702(1)Å, α= 95.38(1), β= 102.72(1), γ= 101.12(1)° and Z= 2. The structural unit comprises one independent copper ion bonded to one half of a trans-oxamidate ligand and one chloride ion. Two centres of symmetry lead to a polymeric molecule. The copper ions are in distorted square-pyramidal environments and the basal co-ordination sites are occupied by O,N,N' donors from the trans-oxamidate ligand and by a chloride ion. The fifth contact occurs with the chloride ion of an adjacent asymmetric unit. The nearest-neighbour Cu ⋯ Cu distance is 3.2989(9)Å and a remarkably acute angle is found at the bridging chloride[79.02(3)°]. The magnetic properties of the compound are well reproduced by the dimer model with pairwise interactions, owing to the overwhelming importance of the oxamidate bridge in determining the exchange coupling interactions [J= 409(3) cm–1]. The EPR spectra, however, indicate that the compound intimately behaves as an alternating chain.

Polynuclear complexes of copper(II). Synthesis, characterization, crystal and molecular structure of the cations bis[oxamidate- N, N′-dipropylamine-2,2′-dimethyl- N, N′, N1, N1′-copper(II)]copper(II) ([CuN 4CuO 4CuN 4] 2+) and bis[oxamidate- N, N′-dipropylamine-2,2′-dimethyl- N, N′, N1, N 1′-copper(II)]dicopper(II)- O, O1, O2, N1, N2-μ-(oxamidate- N, N′-dipropylamine-2,2′-dimethyl- N, N′, O, N1, N1′, O1)([CuN 4(CuN 2O 3) 2CuN 4] 2+) packed in the same crystal as their

The product of the reaction between copper(II) nitrate and oxamidate- N, N′-dipropylamine-2-2′-dimethyl- N, N′, N 1N 1′-copper(II) was isolated and characterized by crystallographic and spectroscopic measurements. The title compound crystallizes in the triclinic space group P1 with cell dimensions a=12.426(1), b=13.405(1), c=15.605(2) Å, α=102.35(1), β=105.34(1), γ=113.74(1)°, Z=1. The crystal consists of tricopper and tetracopper dications packed together in a 1:1 ratio and placed around inversion centres. The tricopper cation contains a central CuO 4 and two outer CuN 4 square units; the copper in the CuN 4 units exhibits a fifth interaction with a nitrate oxygen. The tetracopper cation contains two inner square pyramidal CuN 2O 3 units and two outer CuN 4 square units weakly bound to a fifth nitrate oxygen. The oxamidate ligands exhibit two different conformations and act as hexadentate ligands, with four N donor atoms and two O donor atoms.

Crystal and molecular structure of the six-co-ordinate antimony(III) complex SbCl3,L, where L =N,N′-dimethyloxamide. Unusual O,O ligand binding leading to four-membered Sb(µ-O)2Sb ring formation

Antimony trichloride reacts with N,N′-dimethyloxamide (L) to form SbCl3L. Crystals are triclinic, space group P, Z= 2, with a= 7.492(8), b= 8.954(11), c= 10.544(10)Å, α= 68.1(1), β= 111.0(1), and γ= 111.0(1)°. 1 617 Independent reflections above background were collected on a diffractometer and the structure refined to R 0.065. The unit cell contains two SbCl3 molecules together with two independent oxamide ligands both with an imposed centre of symmetry. The structure is polymeric with the ligands acting as bridges between SbCl3 cores. The antimony atom is strongly bonded to three chlorine atoms [2.400(3), 2.387(3), and 2.350(5)Å] and weakly bonded to three oxygen atoms [2.837(9), 2.722(13), and 2.838(8)Å].

ChemInform Abstract: Magnetic Properties and Crystal Structure of a Linear‐Chain Copper(II) Compound with Bridging Acetate and Oxamidate Ligands.

AbstractThe reaction of diethyloxalate with neopentanediamine in ethanol at O ° Cyields the ligand N,N′‐bis(2‐(aminomethyl)‐2‐methylpropyl)oxamide, which leads by reaction with copper sulfate hydrate to the corresponding Cu complex.

Magnetic properties and crystal structure of a linear-chain copper(II) compound with bridging acetate and oxamidate ligands

Etude du complexe Cu 2 (amoxa)(CH 3 COO) 2 . Cristallisation dans le systeme monoclinique, groupe P2 1 /n et affinement jusqu'a R=0,033. Coordination pyramidale a base carree deformee autour de Cu. Variation avec la temperature de la susceptibilite magnetique. Spectre RPE

Nickel(II) complexes with oxamides. The crystal structure of the nickel(II)-N-(hydroxyethyl)oxamide sodium salt

The title compound crystallizes in the monoclinic space group C 2/c witha = 20.598 A.b = 4.208 A.c = 15.496 A. β = 101.3 and Z = 4. The structure was solved by conventional techniques to an R = 0.051 using 1413 diffractometer data. The accurately square-planar Ni-atom is four-coordinated by deprotonated nitrogen atoms of two substituted oxamide ligands, [L = l-2,N000ONH(CH2)2OH]. Two different nickel-nitrogen bonding distances were observed. indicating that NiII hinds more strongly to a primary than to a secondary nitrogen. The terminal alcohol group is part of the Na-coordination which can be described as a distorted prism. The preparation of the title compound and other homologous complexes is reported.