Spectral, thermal, and X-ray studies on some new bis and tris-hydrazine and hydrazinium metal pyruvates

Some bis-hydrazine metal pyruvates of transition metal ions of the formula M[CH₃COCOO]₂ [N₂H₄]₂, where M = Co, Ni, Zn or Cd, tris-hydrazine metal pyruvates of the formula M[CH₃COCOO]₂ [N₂H₄]₃, where M = Co, Ni, Zn or Cd, and hydrazinium metal pyruvates [N₂H₅]₂M[CH₃COCOO]₄, where M = Co or Ni have been prepared and the compositions of the complexes have been determined by chemical analysis. The magnetic moments and electronic spectra of the complexes suggest a high-spin octahedral geometry for them. Infrared spectral data of bis-hydrazine complexes indicate the bidentate bridging mode shown by hydrazine molecules and mono dentate coordination by pyruvate ions. However, in tris-hydrazine complexes the pyruvate ions are ionic in nature. In hydrazinium complexes two hydrazinium ions and four pyruvate ions show unidentate coordination mode resulting in six coordination around metal ions. Thermo gravimetry and differential thermal analysis in air reveal that most of the complexes decompose in one step to give the respective metal carbonate as the final residue. However, the hydrazinium complexes yield Co₂O₃ or NiO as the residue. The final residues were identified by their X-ray powder data. The X-ray powder diffraction patterns of each series of complexes reveal isomorphism among the series.     

Directed Hamilton Cycle Decompositions of the Tensor Products of Symmetric Digraphs

In this paper, the existence of directed Hamilton cycle decompositions of symmetric digraphs of tensor products of regular graphs, namely, \((K_r \times K_s)^*,\,\,((K_r \circ \overline{K}_s) \times K_n)^*,\,\,((K_r \times K_s) \times K_m)^*,\,\,((K_r \circ \overline{K}_s) \times (K_m \circ \overline{K}_n))^*\) and \((K_{r,r} \times (K_m \circ \overline{K}_n))^*\), where × and ° denote the tensor product and the wreath product of graphs, respectively, are proved. In [16], Ng has obtained a partial solution to the following conjecture of Baranyai and Szász [6], see also Alspach et al. [1]: If D ₁ and D ₂ are directed Hamilton cycle decomposable digraphs, then D ₁ ° D ₂ is directed Hamilton cycle decomposable. Ng [17] also has proved that the complete symmetric r-partite regular digraph, \(K_{r(s)}^{*} = (K_r \circ \overline{K}_s)^*\), is decomposable into directed Hamilton cycles if and only if \((r,s) \ne (4,1)\) or (6, 1); using the results obtained here, we give a short proof of it, when \(r \notin {4,6}\).     

Sputter power and sputter pressure influenced structural and optical behaviour of RF sputtered nanocrystalline ZnO films

Zinc oxide thin films were deposited on p‐type (100) silicon and Corning glass substrate by using RF magnetron sputtering at different sputter powers range 100–200 W and sputter pressures range 2–8 Pa. The deposited films were characterized by X‐ray diffraction, atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscope and UV‐Vis‐NIR spectrophotometer. The films formed at sputter power of 100 W consists of weak (100) reflection and then sputter power increased to 150 W additional (110) reflection was present with enhancement in the intensity of (100) peak. Further increase of sputtering power to 200 W the intensity of (100) phase decreased with the presence of additional peaks of (002) and (101) of ZnO. The FTIR analysis confirms the Zn‐O absorption band was located at 414 cm^‐1. The optical band gap of zinc oxide films decreased from 3.28 to 3.07 eV with increase of sputter power from 100 to 200 W. The maximum crystallite size of 21 nm, the root mean square roughness of 7.2 nm was found at films formed at working pressure of 5 Pa. The optical transmittance of the films increased from 88 to 96% and then decreased to 84% with increase of sputter pressure from 2 to 8 Pa.     

Acetate and malonate complexes of cobalt(II), nickel(II) and zinc(II) with hydrazinium cation

The hydrazinium(1+) metal acetates and malonate dihydrates of the molecular formula [(N₂H₅)₂M(CH₃COO)₄] and (N₂H₅)₂[M(OOCCH₂COO)₂(H₂O)₂] respectively, whereM=Co, Ni or Zn, have been prepared and characterized by chemical analyses, conductance, magnetic, spectral, thermal and X-ray powder diffraction studies. The magnetic moments and electronic spectra indicate that these complexes are of high-spin octahedral variety. The infrared spectra show that the hydrazinium ions are coordinated in the case of acetate complexes, whereas in the malonate complexes the hydrazinium ions are out side the coordination sphere. These complexes undergo exothermic decomposition in the temperature range 150–450°C to give the respective metal oxide as the final residue. The X-ray powder diffraction patterns of the malonate complexes indicate isomorphism among them.     

Preparation and thermal reactivity of some rare earth and uranyl hydrazinesulfinates and sulfite hydrazinates

Hydrazinesulfinate and sulfite hydrazinate derivatives of rare earth elements of composition Ln(N₂H₃SOO)₃(H₂O) and Ln₂(SO₃)₃(N₂H₄)_x(H₂O)_y, respectively, where Ln=La, Ce, Pr, Nd and Sm, have been prepared and characterized by chemical analysis and infrared spectra. The uranyl complexes of the composition UO₂(N₂H₃SOO)₂, UO₂(N₂H₃SOO)₂(N₂H₄) and UO₂SO₃(N₂H₄)(H₂O) have also been prepared under different reaction conditions and studied by different physicochemical techniques. Thermal properties of all these complexes have been studied by thermogravimetry, and differential scanning calorimetry. The hydrazinesulfinate derivatives of rare earth elements undergo thermal decomposition in multisteps to give the respective metal sulfate as the residue. The other series of complexes, viz., rare earth sulfite hydrazinates gave a mixture of metal sulfate and metal oxide as the end products. However, all the uranyl complexes undergo decomposition in air to give UO₂SO₃ as the final product.     

Construction of frustrated Lewis pair from nitride and phosphine for the activation and cleavage of molecular hydrogen

Activation and cleavage of molecular hydrogen (H₂) to proton and hydride is an important task for several reasons, especially as a reagent in hydrogenation. In this scenario, with the support of density-functional theory methods, a novel strategy has been devised for the conversion of coordinated nitride into ammonia using molecular hydrogen in the presence of tri-tert-butylphosphine (P^tBu₃). The proposed methodology is based on the formation of frustrated Lewis pair (FLP) from [Os^VI(tpy)(Cl)₂(N)]⁺ (tpy = 2,2′:6′,2′′-terpyridine ) and P^tBu₃ followed by reaction with molecular hydrogen to form an FLP–H₂ adduct. The FLP–H₂ adduct can further undergo H–H bond cleavage heterolytically to produce proton and hydride which can be eventually used for the functionalization of coordinated nitride to ammonia. The calculated energy profile comprising all possible intermediates and transition-state molecules suggests that the proposed reaction pathway is energetically viable at elevated temperatures.     

Synthesis, spectroscopic characterization and electronic structure of some new Cu(I) carbene complexes

Reaction of oligomeric Cu(I) complexes [Cu(Μ-S-C(=NR)(O-Ar-CH₃)]_n with Lewis acids gave Cu(I) carbene complexes, which were characterized by¹H and¹³C NMR spectroscopy. Cu(I) carbene complexes could be directly generated from RNCS, Cu(I)-OAr and Lewis acids; this method can be used to prepare Cu(I) carbene complexes with different substitutents on the carbene carbon. The complexes were unreactive towards olefins and do not undergo cyclopropanation. Electronic structure calculations (DFT) show that the charge on the carbene carbon plays an important role in controlling the reactivity of the carbene complex.     

Double deprotonation of coordinated ethylimide to CH3CN: molecular mechanism and relevance to the chemistry of Mo and W organoimides

Reaction of [MCl(NEt)(dppe)2)Cl (M = Mo, W) with n-BuLi in tert-butyl methyl ether under an N2 atmosphere yields the M0 bis(dinitrogen) complexes [M(N2)2(dppe)2] and acetonitrile. A mechanism is proposed for this reaction which involves an anionic chloro-acetonitrile intermediate. The implications of these findings to the chemistry of Mo and W organoimides are discussed.     

Understanding the stability, electronic and molecular structure of some copper(III) complexes containing alkyl and non alkyl ligands: Insights from DFT calculations

DFT calculations have been performed for some Cu(III)-alkyl complexes. Complexes 1-19 were optimized to the square planar (sq) geometry and observed no imaginary frequencies. Although formally copper adopts d⁸ configuration (Cu(III)) in all the complexes, the Natural Population Analysis (NPA) revealed that the copper actually in d¹⁰ (Cu(I)) configuration, Bond order calculation suggested that the Cu(III)-Et_trans bond gets more bond order in the presence of poor π-acidic co-ligand (probe ligand). Relatively smaller bond order was calculated for Cu(III)-Me_cis bond than Cu(III)-Et_trans bond and therefore Cu(III)-Et_trans bond is the strongest bond in all the complexes. Calculated less Chemical hardness (η) of complexes 1-19 suggested that all these complexes are less stable in nature. Energy Decomposition Analysis (EDA) revealed that the Cu(III)-Et_trans bond is relatively more stable than the Cu(III)-Me_cis and Cu(III)-L (L = co-ligand/probe ligand) bonds. And also the Cu(III)-alkyl (Cu(III)-Me_cis and Cu(III)-Et_trans) bond in complexes 1-17 is more of ionic in nature. However, Cu(III)-Et_trans bond is relatively more ionic than Cu(III)-Me_cis bond.