O.B. Chanu

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 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 characterization of homotrimetallic copper complexes derived from bis(2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone.

Copper (II) complexes [Cu(3)(nph)(μ(2)-X)(2)(H(2)O)(6)]·2H(2)O [X=Cl (1), (ClO(4)) (3)] and [Cu(3)(nph)(NO(3))(2)(H(2)O)(6)] (2) have been synthesized from bis(2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone in methanol medium and characterized. The structures of the complexes have been discussed in the light of data obtained from analytical, thermoanalytical, mass spectral studies, molar conductance, magnetic moment, electronic, EPR, IR, FT-IR spectroscopic studies. The molar conductance values for the complexes fall in the region 0.5-0.9 Sm(2) mol(-1) in DMSO solution indicating that all of them are non-electrolyte. The magnetic moment values for the complexes suggest weak M-M interaction in the structural unit of the complexes. The dihydrazone ligand is present in enol form in all of the complexes. Copper centre has tetragonally distorted octahedral stereochemistry in chlorido and perchlorato complexes while in nitrato complex, copper has mixed square-pyramidal and distorted-octahedral stereochemistry. The EPR parameters of the complexes indicate that the copper centre has the doublet state as the ground state.

Synthesis and characterization of molybdenum(V,VI) complexes derived from bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone

Monometallic molybdenum(VI) complexes [MoO2(CH2LH2)] · H2O (1), [Mo2O4(CH2LH2)2(A)2] (A = py (2), 2-pic (3), 3-pic (4) and 4-pic (5)) and molybdenum(V) complexes [Mo(CH2LH2)(inh)] · H2O (6) and [Mo(CH2LH2)(slh)] (7) of bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone (CH2LH4) have been synthesized and characterized by various physico-chemical and spectroscopic studies. The compositions of the complexes have been established by elemental analyses and molecular weight determination. The structural assessment of the complexes has been done on the basis of data obtained from molar conductances, magnetic moment studies, electronic, infrared, electron paramagnetic resonance (EPR), proton nuclear magnetic resonance, and 13C proton nuclear magnetic resonance spectroscopic studies. The molar conductance values for the complexes in DMSO suggest that they are non-electrolytes. The magnetic moment values for 6 and 7 correspond to one unpaired electron while the remaining complexes are diamagnetic. Complexes 1, 6, and 7 have six-coordinate octahedral stereochemistry around molybdenum, while 2–5 are eight-coordinate dodecahedral around the metal centers. EPR spectral features suggest that 7 is less symmetrical than 6.

Heterobimetallic dioxomolybdenum(VI) complexes derived from bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone: Synthesis and characterization

The heterobimetallic complexes [MMoO2(L)(H2O)2] (where M = Zn2+ (1), Cu2+ (2), and Co2+ (4)) and [{MMoO3(H2L)(H2O)2}2] (where M = Ni2+ (3) and Mn2+ (5)) are synthesized from bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone (H4L) using the monometallic precursor complex [MoO2(H2L)]·H2O in ethanol. The composition of the complexes is established based on the data obtained from the elemental analysis and molecular weight determinations. The structure of the complexes is discussed in the light of data obtained from molar conductance, magnetic moment, electronic, EPR and IR spectroscopic studies.

Synthesis, characterization, reactivity, and electrochemical studies of manganese(IV) complexes of bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone

Manganese(IV) complexes [MnIV(npah)(H2O)2] (1) and [MnIV(npah)(A)2] · nH2O (where A = py (2), 2-pic (3), 3-pic (4), 4-pic (5)) and MnIV(npah)(NN)] (NN = bpy (6) and phen (7)) have been synthesized from bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone in methanol. The composition of the complexes has been established by elemental analyses. Complex 3 has been characterized by mass spectral data also. Structural assessment of the complexes has been based on data from molar conductance, magnetic moment, electronic, electron paramagnetic resonance, and infrared (IR) spectral studies. Molar conductances of the complexes in DMSO suggest non-electrolytes. Magnetic moment and EPR studies suggest +4 oxidation state for manganese in these complexes. Electronic spectral studies suggest six-coordinate octahedral geometry around the metal ions. IR spectra reveal that H4npah coordinates to the metal in enol form. Reaction of the complexes with benzyl alcohol and SO2 has been investigated. Cyclic voltammetric studies of the complexes have also been carried out.

Characterization of heterobimetallic and mixed-valence complexes of molybdenum(V) derived from bis(2-hydroxy-1-naphthaldehyde) malonoyldihydrazone

Heterobimetallic complexes [UO2MoV(CH2L)(hzd)(H2O)2]n, [ZnMoV(CH2L)(hzd)(H2O)2]n and mixedvalence complexes [MoVIO2MoV(CH2L)(hzd)(H2O)2]n (where hzdH3 = inhH3, n = 1; slhH3, n = 2) are synthesized from bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone (CH2LH4) and monometallic precursor complexes [Mo(CH2LH2)(hzd)]·nH2O (n = 0, 1) in ethanol. The composition of the complexes is established based on the data obtained from the elemental analysis. The structure of the complexes is discussed in the light of data obtained from molar conductance, magnetic moment, electronic, EPR, and IR spectroscopic studies. All complexes have μB values in the range 1.59–1.64 B.M., slightly lower than that required for one unpaired electron. The heterobimetallic complexes show two bands, while mixed-valence complexes show only one band in the visible region assigned to the d-d transition. The g-values decrease in going from uranyl-to-molybdenyl-to-zinc complexes containing the isonicotinoyldiazenido (inh) group, however, no such regular trend is observed in the case of complexes containing the salicyloyldiazenido (slh) group in the coordination sphere. In all complexes, the principal dihydrazone ligand is present in the enol form as a bridging hexadentate ligand in the anti-cis configuration where hydrazide ligands are coordinated to the metal centre as a trinegative bidentate ligand in the diazenido form.