The butoxy- and methoxy-derivatives (HLc, and HLb, respectively) of 1-[(ethoxycarbonyl)methyl]-3-hydroxy-2-(1H)-pyridinone, HLa, were synthesized by transesterification and the mononuclear complexes [MoO2(L(a-c))2] were obtained by the reaction of the ligands with molybdenyl acetylacetonate. The three complexes were fully characterized by (1)H and (13)C NMR spectroscopy, mass spectrometry and elemental analyses. A variable temperature NMR study showed that the N-substituents do not have a significant influence on the racemisation process of the complexes. The comparison of the crystal structure of [MoO2(Lb)2] with [MoO2(La)2] confirmed that an additional methylene group does not affect the immediate coordination environment of the molybdenum centre. The methoxy-derivative HLb was also found to produce a dinuclear complex of composition [(MoO2(Lb)O)2], the structure of which was determined by X-ray diffraction.
Caged peroxide: An octanuclear nickel complex, which exhibits peroxide in an unprecedented μ6‐(η1)3 coordination mode, was prepared (see structure: only the Ni8 unit with the central peroxo ligand and the bridging oxygen atoms is shown; green Ni, red O). This mode of binding finally completes the series of symmetrical μn‐(η1)n/2 peroxide binding modes in complexes.
Peroxid eingefroren in perfekter Symmetrie, die beim Blick entlang der Hauptachse an eine Schneeflocke denken lässt, findet man in einem näherungsweise S6‐symmetrischen achtkernigen Nickelkomplex (der Ni‐O‐Kern ist im Vordergrund zu sehen; Ni grün, O rot). Der Einschluss als μ6‐koordinierter Peroxoligand im Nickelkäfig stabilisiert diese reaktive Spezies. Weitere Informationen finden Sie in der Zuschrift von A.‐K. Duhme‐Klair, P. H. Walton et al. auf S. 1416 ff. (Für das Hintergrundbild danken die Autoren Prof. K. G. Libbrecht, Caltech.)
Elimination reactions of enol sulphonates have been further studied. The enol sulphonates of p-anisoyl-, 2-furoyl-, and 2-thenoyl-malonic esters readily gave the corresponding propiolic acids on treatment with base, whereas the enol sulphonates of o-, rn-, and p-nitrobenzoylmalonic esters gave negligible yields. The enol sulphonates of cyclopropylcarbonylmalonate gave cyclopropylpropiolic acid, while those of trichloroacetylmalonate and fumaroylmalonate gave no acetylenic product. acetylene.
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