Reactions of quinquedentate Schiff base ligands with Mn and Cu ions afforded icosa- and hexadecanuclear mixed-metal clusters in which dinuclear CuII complexes trapped oxo-bridged [MnIII8MnIV4O12] and [MnIII6O6] cores, respectively. Maximum entropy method analysis for synchrotron X-ray diffraction data was used to determine the oxidation states of the Mn ions.
MCM-41 (#41 Mobil Composition of Matter) is a favorable material for heterogeneous reactions because of its unique porous structure. However, the catalytic activity of MCM-41 for the oxidative dehydrogenation (ODH) of isobutane to isobutene is known to be quite low. In the present study, a metal-doping method was employed to improve this catalytic activity. Doping of Cr, Co, Ni, or Mo into MCM-41 resulted in a great improvement in the catalytic activity. Since chromium-doped MCM-41 (Cr-MCM-41) showed the greatest catalytic activity among these catalysts, its redox property was further analyzed via XPS, XAFS and H 2-TPR techniques. The XPS spectrum of Cr-MCM-41 suggested that it has Cr 3+ and Cr 6+ species on its surface. Also, a pre-edge peak due to Cr 6+ species was confirmed in the XANES spectrum of Cr-MCM-41. In H 2-TPR measurement, Cr-MCM-41 was more reducible than crystalline Cr 2 O 3 , which showed low catalytic activity for the ODH of isobutane. The reducible Cr 6+ species on Cr-MCM-41 contributed to an improvement in the catalytic activity of MCM-41.
The study on the synthesis of π‐conjugated polymers using cobaltacyclopentadiene formation reaction of CpCo(PPh3)2 and conjugated diacetylene and the structure and physical properties of the polymers is overviewed. The substituents on the diacetylene affect crucially the solubility, the degree of polymerization, redox properties, and electronic structures and so on. Recent synthesis of a ruthenacyclopentatriene polymers by metallacyling polymerization is also described.
A ruthenacyclopentatriene polymer 2 was synthesized by metallacycling polymerization (MCP). Polymer 2 with Mn = 3400 and Mw = 5800 consisted of identical ruthenacyclopentatriene units. The UV-vis spectra of 2 showed a shift of the pi-pi* band to a longer wavelength due to the enlargement of the pi-conjugation. Polymer 2 underwent reversible reduction due to the ruthenacycle moiety at -1.01 V versus ferrocenium/ferrocene. The EPR spectrum of the reduced form of 2 in frozen THF indicated ferromagnetic interaction of spins at ruthenacyclopentatriene units.
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