Ram A. Lal

Synthesis and spectral studies of nickel(II) complexes derived from disalicylaldehyde oxaloyldihydrazone

The mononuclear nickel(II) complex [Ni(H2slox)(H2O)3] (1) and polymeric dinuclear complexes [Ni2(slox)(A4)] {A = H2O (2), py (3), 2-pic (4), 3-pic (5) and 4-pic (6)} and the discrete binuclear complexes [Ni2(slox)(NN)3] {NN = bpy (7) and phen (8)} have been synthesized from disalicylaldehyde oxaloyldihydrazone (H4slox) in methanol. All of the complexes are nonelectrolytes. Complexes 1, 7, and 8 are paramagnetic while binuclear 2–6 possess anomalously low μ eff value, indicating considerable metal–metal interaction. Discrete binuclear 7 and 8 have no interaction between the two nickel(II) ions. The anomalously low magnetic moment values in 2–6 are explained as metal–metal interaction via phenoxide bridge. Such metal–metal interactions are less in 7 and 8 due to coordination of bipyridine and phenanthroline molecules which do not allow phenoxide bridging. The dihydrazone coordinates to the metal center as a dibasic tridentate ligand in keto-enol form in staggered configuration in 1, while in the remaining complexes the dihydrazone is tetrabasic hexadentate in enol form in anticis configuration. The metal center has a tetragonally distorted octahedral stereochemistry.

Synthetic and spectroscopic investigations of some dioxouranium(VI) complexes of multidentate disalicylaldehyde adipoyldihydrazone

Abstract Reactions of disalicylaldehyde adipoyldihydrazone with uranyl acetate dihydrate and uranyl nitrate hexahydrate in aqueous and ethanolic media under different experimental conditions were studied and the resulting complexes with the compositions [UO2(H2L2)(H2O)]n,[UO2(H2L2)]inn,3nH2O, [UO2(H3L2)(CH3COO)]n3nH2O, [UO2Zn(L2) (H2O)2]n2nH2O, [(UO2)2(H2L2)(C2O4)]n2nH2O and [(UO2)2(L2)(py)2(H2O)4] were characterized on the basis of elemental analyses, EDAX and thermoanalytical data. The structural assessment of the complexes was carried out by using molar conductance, magnetic moment and ESR data and IR, electronic and 1H NMR spectroscopy. In the complexes, the ligand functions as a bridging monobasic tetradentate, dibasic hexadentate and tetrabasic hexadentate ligand, and exhibits keto-enol tautomerism. The acetate and oxalate groups act as chelating bidentate and bridging tetradentate ligands. The complexes are considered to involve seven, eight, nine and ten coordinated uranium atoms with ligand atoms arranged in the equatorial plane around the linear uranyl group and in the heterobimetallic complex [UO2Zn(L2)(H2O)2]n2nH2O the zinc atom is considered to have tetrahedral stereochemistry.

Synthesis of homobimetallic molybdenum(VI) complex of bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone and its reaction with electron and proton bases

The diamagnetic dioxomolybdenum(VI) complex [(MoO(2))(2)(CH(2)L)(H(2)O)(2)]H(2)O (1) has been isolated in solid state from reaction of MoO(2)(acac)(2) with bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone (CH(2)LH(4)) in 3:1 molar ratio in ethanol at higher temperature. The reaction of the complex (1) with electron donor bases gives diamagnetic molybdenum(VI) complexes having composition [Mo(2)O(5)(CH(2)LH(2))].2A.2H(2)O (where A=pyridine (py, 2), 2-picoline (2-pic, 3), 3-picoline (3-pic, 4), 4-picoline (4-pic, 5)). Further, when the complex (1) is allowed to react with protonic bases such as isonicotinoylhydrazine (inhH(3)) and salicyloylhydrazine (slhH(3)), reduction of molybdenum(VI) centre occurs leading to isolation of homobimetallic molybdenum(V) complexes [Mo(2)(CH(2)L)(inh)(2)(H(2)O)(2)] (6) and [Mo(2)(CH(2)L)(slh)(2)] (7), respectively. The composition of the complexes has been established by analytical, thermo-analytical and molecular weight data. The structure of the molybdenum(VI) complexes (1)-(5) has been established by electronic, IR, (1)H NMR and (13)C NMR spectral studies while those of the complexes (6) and (7) by magnetic moment, electronic, IR and EPR spectral studies. The dihydrazone is coordinated to the metal centres in staggered configuration in complex (1) while in anti-cis configuration in complexes (2)-(7). The complexes (6) and (7) possess magnetic moment of 2.95 and 3.06 BM, respectively, indicating presence of two magnetic centre in the complexes per molecule each with one unpaired electron on each metal centre without any metal-metal interaction. The electronic spectra of the complexes are dominated by strong charge transfer bands. All of the complexes involve six coordinated molybdenum centre with octahedral arrangement of donor atoms except in the complex (6), in which the molybdenum centre has rhombic arrangement of ligand donor atoms. The probable mechanism for generation of oxo-group in the complexes (2)-(5) involving coordinated water molecule has been proposed.

Synthesis and characterization of manganese(IV) and ruthenium(III) complexes derived from bis (2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone

Bis(2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone(naohH4) interacts with manganese(II) acetate in methanol followed by addition of KOH giving [MnIV(naoh)(H2O)2]. Activated ruthenium(III) chloride reacts with naohH4 in methanol yielding [RuIII(naohH4)Cl(H2O)Cl2]. The replacement of aquo by heterocyclic nitrogen donor in these complexes has been observed when the reaction is carried out in presence of heterocyclic nitrogen donors such as pyridine(py), 3-picoline(3-pic) or 4-picoline(4-pic). The molar conductance values in DMF for these complexes suggest non-electrolytic nature. Magnetic moment values suggest +4 oxidation state for manganese in its complexes, however, ruthenium(III) complexes are paramagnetic with one unpaired electron. Electronic spectral studies suggest six coordinate metal ions. IR spectra reveal that naohH4 coordinates in enol-form and keto-form to manganese and ruthenium, respectively. ESR and cyclic voltammetric studies of the complexes have also been reported.

Polymeric dioxouranium(VI) complexes with acyldihydrazones

Abstract Dioxouranium(VI) complexes of disalicylaldimine oxamide (H 4 A), malonamide, (H 4 B), succinamide (H 4 C), glutaramide (H 4 D), adipamide (H 4 E), and phthalamide (H 4 F) have been synthesized in aqueous alcoholic media and characterized by elemental analyses, decomposition temperature, thermoanalytical data, molar conductances, infrared and Raman spectral data. The complexes conform to composition (UO 2 ) 2 (L)·6H 2 O (where H 4 L=H 4 A, H 4 B, H 4 C, H 4 D, H 4 E, H 4 F). The infrared spectral data indicate that the ligands coordinate to the uranyl group in the enol form through enolized carbonyl oxygen, azine group nitrogen and phenolic oxygen, and suggest that the ligands function as tetrabasic hexadentate ligands. The position of the phenolic oxygen group is diagnostic of the presence of an oxo-bridge. Polymerization arises through ligands as well as oxo- bridging. The infrared and Raman spectra indicate that the linearity of the UO 2 2+ group is maintained in all these complexes with the ligand atoms arranged in the equatorial plane perpendicular to the linear uranyl group. It has been found that all the complexes show only one band due to asymmetric stretching vibration of the uranyl group, indicating the same coordination environment around the uranium atom in the complexes and thus suggesting that the two hydrazone parts of the ligands are attached to different uranyl groups in a symmetrical linear fashion. Further it has been observed that the asymmetric stretching frequency of the uranyl group decreases with an increase in the number of methylene groups between the two C=O groups. From this the effect of increasing the number of methylene groups on the coupling between two C=O groups has been discussed. It has been found that the phenyl ring in the phthalamide complex shows electron- withdrawing capacity on the phenyl group of the two salicylaldiminato units.

Synthesis and characterization of a binuclear copper(II) complex [Cu(H2slox)]2 from polyfunctional disalicylaldehyde oxaloyldihydrazone and its heterobinuclear copper(II) and molybdenum(VI) complexes

The binuclear copper complex [Cu(H2slox)]2 (1) and heterobinuclear copper and molybdenum complexes [Cu(slox)MoO2(A)2] (slox = tetranegative disalicylaldehyde oxaloyldihydrazone) (A = H2O (2), py (3), 2-pic (4), 3-pic (5), 4-pic (6)) and [Cu(slox)MoO2(NN)] (NN = bpy (7) and phen (8)) have been synthesized from disalicylaldehyde oxaloyldihydrazone in methanol and characterized by various physico-chemical and spectroscopic techniques. The stoichiometry of the complexes has been established based on elemental analyses and thermoanalytical studies. The µ eff values for the complexes rule out metal–metal interaction between the metal centers in the structural unit of the complexes. The dihydrazone has keto-enol forms; in 1, it is a dibasic tetradentate bridging ligand in enol form and in heterobinuclear complexes as a tetrabasic hexadentate bridging ligand. Electronic spectra of the complexes show that copper(II) is square-planar in binuclear and heterobinuclear complexes; molybdenum is a distorted octahedral stereochemistry in heterobinuclear complexes. EPR spectra suggest that in all complexes, the unpaired electron is in the d x 2− y 2 orbital of copper and that the copper in heterobinuclear complexes is tetrahedrally distorted.

Synthesis, characterization and electrochemical properties of bis(μ2-perchlorato)tricopper(II) complexes derived from succinoyldihydrazones

Three new homotrimetallic copper(II) complexes ([Cu3(Ln)(ClO4)2(H2O)m] with H4Ln = H4L1 − H4L3, m = 0, 3) have been synthesized from substituted succinoyldihydrazones (H4Ln) in methanol. The composition of the complexes has been established on the basis of data obtained from analytical and mass spectral studies and molecular weight determination in DMSO. The structure of the complexes has been discussed in the light of molar conductance, magnetic moment data and electronic, EPR, IR and FT-IR spectral studies. The molar conductance values for the complexes in the region of 1.2–1.7 Ω−1 cm2 mol−1 in DMSO indicate that the complexes are nonelectrolytes. The magnetic moment values for the complexes suggest considerable metal–metal interaction in the structural unit of the complexes. Copper centres have square planar and square pyramidal stereochemistry. The EPR parameters of complexes 1 and 3 indicate that the copper centre has a doublet ground state, while for complex 2, the ground state is a mixture of both doublet and quartet states. Electron transfer reactions of the complexes have been investigated by cyclic voltammetry.

Synthesis and spectral characterization of homobimetallic molybdenum(VI) complexes derived from bis(2-hydroxy-1-naphthaldehyde)succinoyldihydrazone

The reaction of bis(2-hydroxy-1-naphthaldehyde)succinoyldihydrazone with bis(acetylacetonato)dioxomolybdenum(VI) (MoO2(acac)2) in 1 : 3 molar ratio in EtOH : water mixture (95 : 5) affords a complex of composition [(MoO2)2(nsh)(H2O)2] · C2H5OH. The reaction of [(MoO2)2(nsh)(H2O)2] · C2H5OH with Lewis bases, namely pyridine, 2-picoline, 3-picoline, and 4-picoline, yields [(MoO2)2(nsh)(B)2] · C2H5OH (where B = pyridine, 2-picoline, 3-picoline, and 4-picoline). Further, when this complex was reacted with 1,10-phenanthroline and 2,2′-bipyridine in 1 : 3 molar ratio in anhydrous ethanol the binuclear complexes [(μ2-O)2(MoO2)2(H4nsh)(phen)] · C2H5OH and [(μ2-O)2(MoO2)2(H4nsh)(bpy)] · C2H5OH were obtained. All of the complexes have been characterized by analytical, magnetic moment, and molar conductivity data. The structures of the complexes have been discussed in the light of electronic, IR, 1H NMR, and 13C NMR spectroscopy.

Synthesis and characterization of heterobimetallic Ni(II)–Zn(II) complexes from bis(2-hydroxy-1 -naphthaldehyde)succinoyldihydrazone

Monometallic zinc(II) and nickel(II) complexes, [Zn(H2nsh)(H2O)] (1) and [Ni(H2nsh)(H2O)2] (2), have been synthesized in methanol by template method from bis(2-hydroxy-1-naphthaldehyde)succinoyldihydrazone (H4nsh). Reaction of monometallic complexes with alternate metal(II) acetates as a transmetallator in 1 : 3 molar ratio resulted in the formation of heterobimetallic complexes [NiZn(nsh)(A)3] and [ZnNi(nsh)(A′)2] (A = H2O (3), py (4), 2-pic (5), 3-pic (6), 4-pic (7)), (A′ = H2O (8), py (9), 2-pic (10), 3-pic (11), and 4-pic (12)). The complexes have been characterized by elemental analyzes, mass spectra, molar conductance, magnetic moments, electronic, EPR, and IR spectroscopies. All of the complexes are non-electrolytes. Monometallic zinc(II) is diamagnetic while monometallic nickel(II) complex and all heterobimetallic complexes are paramagnetic. The metal centers in heterobimetallic complexes are tethered by dihydrazone and naphthoxo bridging. Zinc(II) is square pyramidal; nickel(II) is six-coordinate distorted octahedral except [ZnNi(nsh)(A)2], in which nickel(II) has square-pyramidal geometry. The displacement of metal center in monometallic complexes by metal ion has been observed in the resulting heterobimetallic complexes.

Synthesis and spectral studies on heterobimetallic complexes of manganese and ruthenium derived from N-(2-hydroxynaphthalen-1-yl)methylenebenzoylhydrazide

The complex [MnIV(napbh)2] (napbhH2 = N-(2-hydroxynaphthalen-1-yl)methylenebenzoylhydrazide) reacts with activated ruthenium(III) chloride in methanol in 1 : 1.2 molar ratio under reflux, giving heterobimetallic complexes, [MnIV(napbh)2RuIIICl3(H2O)] · [RuIII(napbhH)Cl2(H2O)] reacts with Mn(OAc)2·4H2O in methanol in 1 : 1.2 molar ratio under reflux to give [RuIII(napbhH)Cl2(H2O)MnII(OAc)2]. Replacement of aquo in these heterobimetallic complexes has been observed when the reactions are carried out in the presence of pyridine (py), 3-picoline (3-pic), or 4-picoline (4-pic). The molar conductances for these complexes in DMF indicates 1 : 1 electrolytes. Magnetic moment values suggest that these heterobimetallic complexes contain MnIV and RuIII or RuIII and MnII in the same structural unit. Electronic spectral studies suggest six coordinate metal ions. IR spectra reveal that the napbhH2 ligand coordinates in its enol form to MnIV and bridges to RuIII and in the keto form to RuIII and bridging to MnII.