Synthesis and structural characterization of ruthenium(II) carbonyl complexes with a bistriazole N-heterocyclic carbene ligand

Comparison of the Spectroscopically Measured Catalyst Transformation and Electrochemical Properties of Grubbs' First- and Second-Generation Catalysts

According to UV-vis spectroscopy (0.10 mM, CH₂Cl₂ at 25 °C), the catalyst transformation (which could possibly include ligand dissociation with active catalyst formation, dimer formation, and decomposition) rate constants (k _obs) of Grubbs' first (1) and second (2) generation catalysts are 7.48 × 10^-5 and 1.52 × 10^-4 s^-1, respectively. From ³¹P NMR (0.1 M, CD₂Cl₂, at 25 °C), the catalyst transformation was 5.1% for 1 and 16.5% for 2 after 72 h. However, due to the larger concentrations of the NMR samples compared to the UV-vis samples, the extent of transformation did not correspond. The oxidation potential of the Ru^II/Ru^III couple of 2 (E°' = 27.5 mV at v = 200 mV s^-1) was considerably lower than that of 1 (E°' = 167 mV at v = 200 mV s^-1). In the case of 1, a second reduction peak appeared at slow scan rates. This may probably be ascribed to an electrochemically active compound that was formed from the intermediate cation 1 ^•+ and the subsequent reduction of the latter. The oxidation/reduction of 1 proceeds according to an E_rC_i electrochemical mechanism (E_r = electrochemically reversible step, C_i = chemically irreversible step), whereas 2 proceeds according to an E_rC_r electrochemical mechanism (E_r = electrochemically reversible step, C_i = chemically reversible step).

Synthesis and crystal structure of a two-dimensional sodium coordination polymer of 4,4'-(diazenediyl)bis(1H-1,2,4-triazol-5-one)

The crystal engineering of coordination polymers has aroused interest due to their structural versatility, unique properties and applications in different areas of science. The selection of appropriate ligands as building blocks is critical in order to afford a range of topologies. Alkali metal cations are known for their mainly ionic chemistry in aqueous media. Their coordination number varies depending on the size of the binding partners, and on the electrostatic interaction between the ligands and the metal ions. The two-dimensional coordination polymer poly[tetra-μ-aqua-[μ4-4,4'-(diazenediyl)bis(5-oxo-1H-1,2,4-triazolido)]disodium(I)], [Na2(C4H2N8O2)(H2O)4]n, (I), was synthesized from 4-amino-1H-1,2,4-triazol-5(4H)-one (ATO) and its single-crystal structure determined. The mid-point of the imino N=N bond of the 4,4'-(diazenediyl)bis(5-oxo-1H-1,2,4-triazolide) (ZTO(2-)) ligand is located on an inversion centre. The asymmetric unit consists of one Na(+) cation, half a bridging ZTO(2-) ligand and two bridging water ligands. Each Na(+) cation is coordinated in a trigonal antiprismatic fashion by six O atoms, i.e. two from two ZTO(2-) ligands and the remaining four from bridging water ligands. The Na(+) cation is located near a glide plane, thus the two bridging O atoms from the two coordinating ZTO(2-) ligands are on adjacent apices of the trigonal antiprism, rather than being in an anti configuration. All water and ZTO(2-) ligands act as bridging ligands between metal centres. Each Na(+) metal centre is bridged to a neigbouring Na(+) cation by two water molecules to give a one-dimensional [Na(H2O)2]n chain. The organic ZTO(2-) ligand, an O atom of which also bridges the same pair of Na(+) cations, then crosslinks these [Na(H2O)2]n chains to form two-dimensional sheets. The two-dimensional sheets are further connected by intermolecular hydrogen bonds, giving rise to a stabile hydrogen-bonded network.

A new Co(II) complex of diniconazole: synthesis, crystal structure and antifungal activity

A new Co(II) complex of diniconazole, namely diaqua[(E)-(RS)-1-(2,4-dichlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl-κN(4))pent-1-en-3-ol]cobalt(II) dinitrate dihydrate, [Co(C15H17Cl2N3O)3(H2O)2](NO3)2·2H2O, was synthesized and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Crystal structural analysis shows that the centrosymmetric Co(II) cation is coordinated by four diniconazole ligands and two water molecules, forming a six-coordinated octahedral structure. There are also two free nitrate counter-anions and two additional solvent water molecules in the structure. Intermolecular O-H...O hydrogen bonds link the complex cations into a one-dimensional chain. In addition, the antifungal activity of the complex against Botryosphaeria ribis, Gibberella nicotiancola, Botryosphaeria berengriana and Alternariasolani was studied. The results indicate that the complex shows a higher antifungal activity for Botryosphaeria ribis and Botryosphaeria berengriana than diniconazole, but a lower antifungal activity for Gibberella nicotiancola and Alternariasolani.