Subbaiah Govindarajan

Studies on bis(Hydrazine) Metal Malonates and Succinates

Abstract Several new bis(hydrazine) complexes of metal malonates and succinates of the formula MX(N2H4)2 (M = Co, Ni, Zn and Cd; X = malonate or succinate) have been prepared and characterized by chemical analyses and magnetic and spectral studies. The magnetic moments and electronic spectra indicate that these complexes are of high spin octahedral variety Infrared spectra show the bidentate nature of both the hydrazine and malonate/succinate moities The thermal degradation (TG and DTA) of the compounds yield metal oxides as the final residue. X-ray powder diffraction patterns show that each series of compounds are isomorphous among themselves. Referee I: P. J. Toscano Referee II: W. H. Watson

Formato Complexes of Co(II), Ni(II) and Zn(II) with the Hydrazinium(1+) Cation

Abstract Hydrazinium formate hemihydrate reacts with transition metal ions M2+ to form complexes of the formula [N2H5)2M(HCOO)4].H2O (M = Co, Ni and Zn). The complexes were characterized by chemical analyses conductivity and magnetic susceptibility measurements and electronic and infrared spectroscopy. The thermal decomposition of the compounds has been studied using simultaneous DTA-TG-DTG. In all the complexes the metal ion is octahedral with two coordinated hydrazinium(1+) cations and four monodentate formate anions. The X-ray powder patterns show that the three complexes are isomorphous.

Preparation and thermal reactivity of hydrazinium uranyl carboxylates

Abstract Hydrazinium uranyl carboxylates with the formula N 2 H 5 [UO 2 L 3 ]· n H 2 O, where for L = salicylate, n = 4; for L = benzoate and p -hydroxybenzoate, n = 2; for L = hydrazinecar-boxylate, n = 1; for L = acetate, propionate and thioglycolate, n = 0, and dihydrazinium uranyl phthalate (N 2 H 5 ) 2 [UO 2 ( o -C 6 H 4 (COO) 2 ) 2 ] have been prepared in aqueous media. The electronic spectra of the complexes confirm the presence of the uranyl cation in the molecules. The infrared spectra of the complexes show the NN stretching frequency of N 2 H 5 + in the range of 970–980 cm −1 confirming its ionic nature. The small separation ( Δν −1 ) between the asymmetric and symmetric stretching vibrations of the carboxylate groups in all the complexes except hydrazinecarboxylate and phthalate compounds, reveals the bidentate chelate coordination of the carboxylate groups. The hydrazinecarboxylate group is coordinated through O and N atoms as a bidentate chelate. IR frequencies also show that one of the carboxylates in the phthalate complex is a monodentate and the other is bidentate chelate. Thus the phthalate ligand bridges in both uni- and bidentate fashion. Simultaneous TG-DTA shows that the aromatic carboxylate complexes, including hydrazinium uranyl hydrazinecarboxylate monohydrate, decompose exothermically whereas the aliphatic counterparts decompose both endo- and exothermically. Except for N 2 H 5 [UO 2 (N 2 H 3 COO) 3 )·H 2 O all other complexes decompose via uranyl carboxylate intermediate to give U 3 O 8 as the final product. The water molecules are lost endothermically at low temperature (around 100°C) indicating the presence of water molecules as water of crystallisation.

Reaction of Dihydrazinium Ethylenediaminetetraacetate with Nitrates of Co(II), Ni(II), Cu(II) and Zn(II)

Abstract The dihydrazinium ethylenediaminetetraacetate, (N2H5)2 (H2edta) reacts with metal nitrates to form complexes of the type, N2H5[M(Hedta)˙H2O], where M = Co(II), Ni (II), Cu(II) or Zn (II). These complexes were characterised by analytical data, conductivity and magnetic susceptibility measurements, electronic and infrared spectroscopy and thermal analyses. The complexes are 1:1 electrolytes in aqueous solution.

Cationic, neutral and anionic metal(II) complexes derived from 4-oxo-4H-­pyran-2,6-dicarboxylic acid (chelidonic acid)

The structures of five metal complexes containing the 4-oxo-4H-pyran-2,6-dicarboxylate dianion illustrate the remarkable coordinating versatility of this ligand and the great structural diversity of its complexes. In tetraaquaberyllium 4-oxo-4H-pyran-2,6-dicarboxylate, [Be(H(2)O)(4)](C(7)H(2)O(6)), (I), the ions are linked by eight independent O-H...O hydrogen bonds to form a three-dimensional hydrogen-bonded framework structure. Each of the ions in hydrazinium(2+) diaqua(4-oxo-4H-pyran-2,6-dicarboxylato)calcate, (N(2)H(6))[Ca(C(7)H(2)O(6))2(H2O)2], (II), lies on a twofold rotation axis in the space group P2/c; the anions form hydrogen-bonded sheets which are linked into a three-dimensional framework by the cations. In bis(mu-4-oxo-4H-pyran-2,6-dicarboxylato)bis[tetraaquamanganese(II)] tetrahydrate, [Mn2(C(7)H(2)O(6))2(H2O)(8)].4H2O, (III), the metal ions and the organic ligands form a cyclic centrosymmetric Mn2(C(7)H(2)O(6))2 unit, and these units are linked into a complex three-dimensional framework structure containing 12 independent O-H...O hydrogen bonds. There are two independent Cu(II) ions in tetraaqua(4-oxo-4H-pyran-2,6-dicarboxylato)copper(II), [Cu(C(7)H(2)O(6))(H2O)4], (IV), and both lie on centres of inversion in the space group P1; the metal ions and the organic ligands form a one-dimensional coordination polymer, and the polymer chains are linked into a three-dimensional framework containing eight independent O-H...O hydrogen bonds. Diaqua(4-oxo-4H-pyran-2,6-dicarboxylato)cadmium monohydrate, [Cd(C(7)H(2)O(6))(H2O)2].H2O, (V), forms a three-dimensional coordination polymer in which the organic ligand is coordinated to four different Cd sites, and this polymer is interwoven with a complex three-dimensional framework built from O-H...O hydrogen bonds.

Syntheses and coordination isomerism of heteroleptic divalent-metal (M = Co, Zn) carbazate complexes

Three heteroleptic divalent-metal alkyl-carbazate-thiocyanate complexes, [M(NCS)2(NH2NHCOOR)2] [M = Co and R = CH2CH3 (1); M = Co and R = CH3 (2); M = Zn and R = CH3 (3)], have been prepared and characterized, and their crystal structures determined. In 1, Co(II) adopts a fairly regular centrosymmetric trans-CoO2N4 octahedral geometry arising from its coordination by two N,O-bidentate ethylcarbazate ligands and two trans N-bonded thiocyanates. In isostructural 2 and 3, the metals adopt distorted cis-MO2N4 octahedral geometries arising from two N,O-bidentate methylcarbazate ligands with cis N-bonded thiocyanates. The crystal structures feature N–H⋯O and N–H⋯S interactions. Thermal analysis data show that these compounds begin to decompose at temperatures between 130 and 160 °C. Crystal data: 1, CoC8H16N6O4S2, Mr = 383.32, P21/n (No. 14), a = 5.2599(3) Å, b = 7.4209(4) Å, c = 20.1948(12) Å, β = 94.070(1)°, V = 786.28(8) Å3, Z = 2, R(F) = 0.028, wR(F2) = 0.073; 2, CoC6H12N6O4S2, Mr = 355.27, P21/n (No. 14), a = 7.8663(3) Å, b = 10.5804(3) Å, c = 17.6313(5) Å, β = 102.019(10)°, V = 1435.26(8) Å3, Z = 4, R(F) = 0.036, wR(F2) = 0.097; 3, ZnC6H12N6O4S2, Mr = 361.71, P21/n (No. 14), a = 7.8883(2) Å, b = 10.5756(3) Å, c = 17.5827(5) Å, β = 101.676(1)°, V = 1436.46(7) Å3, Z = 4, R(F) = 0.031, wR(F2) = 0.084. Graphical Abstract

Coordination Compounds of Some Divalent Metals with Hydrazine and Dicarboxylate Bridges

Abstract Metal hydrazine dicarboxylates of cobalt, nickel, zinc and cadmium with pimelic, suberic, azelaic and sebacic acids have been prepared and characterised by analytical, spectral, thermal and X-ray powder diffraction studies. IR data augment the bridging behaviour of both the hydrazine and the long chain dicarboxylate dianion except in the case of the cadmium pimelate compound. The most probable stereochemistry of the polymeric compounds has been ascribed on the basis of the available spectral and thermal data. Almost all of the complexes decompose to give its metal oxide through their metal dicarboxylate intermediates. The dihydrazine complexes of the metals with their respective anions are isomorphous among themselves.

Synthesis, Characterization and Thermal Analysis of Metal Hydrazinesulfinates

Abstract Metal hydrazinesulfinates of the formula M(N2H3SOO)2, where M is Mn, Fe, Co, Ni, Zn and Mg have been prepared by passing sulfur dioxide gas through an aqueous solution of metal salt and hydrazine hydrate. Four coordination of the metal ions are proposed on the basis of magnetic, visible and infrared spectral data. The thermal analyses of these compounds show an exothermic decomposition to give metal sulfites in the cases of the Fe, Co, Zn and Mg compounds, whereas the Mn and Ni compounds give metal sulfates. The X-ray powder diffraction patterns indicate that the compounds are isomorphous. Referee I: A. G. McKenna Referee II: K. Moedritzer

A family of double-layered coordination polymers containing Cd2+, N,O-chelating ligands, and bridging SCN− and Cl−

The syntheses, structures, and characterization (IR, TGA/DTA) of a family of layered coordination polymers containing Cd2+, bridging anions (SCN− and Cl−), and chelating C2H6N2O2 methyl carbazate (mc) and C3H8N2O2 ethyl carbazate (ec) ligands are described, viz: Cd(SCN)2(C2H6N2O2), Cd(SCN)Cl(C2H6N2O2), Cd(SCN)2(C3H8N2O2), and Cd(SCN)Cl(C3H8N2O2). Single-crystal structures show them to contain distorted CdN3OS2 (for the thiocyanate) and CdN2OCl2S (for the thiocyanate/chloride) octahedra, in which the mc and ec ligands adopt an N,O-bidentate coordination mode, and the four anions bridge adjacent metal ions, which leads to polymeric sheets built up from double-octahedral layers propagating in the (1 0 0) plane. The topological linkage of the metal ions, which is the same in each structure, can be described as a distorted hexagonal grid. The crystal structures are completed by weak N–H⋯O, N–H⋯N, N–H⋯Cl, and N–H⋯S hydrogen bonds, which all occur within the (1 0 0) polyhedral layers. Graphical abstract

Preparation and Characterisation of Glutarate and Adipate Complexes of Metals with Neutral Hydrazine

Abstract New metal glutarate dihydrazinate hydrates of the types; M(C5H6O4).2N2H4.H2O, where M is Co(ll) and Ni(ll), Zn(C5H6O4).2N2H4.2H2O and Cd(C5H6O4).2N2H4.5H2O and metal adipate dihydrazinates of the formula M(C6H8O4).2N2H4, where M is Co(ll), Ni(ll), Zn(ll) and Cd(ll), have been prepared and characterised by spectral, magnetic, XRD and thermal studies. Infrared spectra reveal the bidentate coordination of both hydrazine and dicarboxylate moities. The magnetic and electronic spectral data indicate octahedral coordination for the cobalt and nickel compounds. The simultaneous TGA-DTA data show that all of the complexes decompose via the respective metal glutarate or adipate intermediates undergoing exothermic decomposition to give metal oxide as the residual product. The loss of hydrazine is exothermic for the cobalt and nickel compounds, whereas it is endothermic for the zinc and cadmium compounds. The X-ray powder diffraction patterns of the similar type of complexes indicate isomorphism among themselves