Early-Transition-Metal Complexes of Functionalized Nonagermanide Clusters: Synthesis and Characterization of [Cp2(MeCN)Ti(η1-Ge9{Si(TMS)3}3)] and K3[Cp2Ti(η1-Ge9{Si(TMS)3}2)2].

Anionic clusters with a homoatomic [Ge9] core are species with Ge atoms in low oxidation states. In this study their reaction with early-transition-metal complexes was investigated. We report the syntheses of Ti(III) complexes of silylated [Ge9] Zintl clusters, which are rare examples of molecular complexes with Ge-Ti interactions. The neutral species [Cp2(MeCN)Ti(η1-Ge9{Si(TMS)3}3)] (1) was obtained by the reaction of K[Ge9{Si(TMS)3}3] with [Cp2TiCl]2 in toluene as dark orange crystals, whereas the reaction of K2[Ge9{Si(TMS)3}2] with [Cp2TiCl]2 in thf and subsequent recrystallization from toluene resulted in dark green crystals of K3[Cp2Ti(η1-Ge9{Si(TMS)3}2)2] (2). Compound 2 contains the trianion [Cp2Ti(η1-Ge9{Si(TMS)3}2)2]3- (2a), which can be described either as a [Cp2Ti]+-bridged [Ge9{Si(TMS)3}2]2- dimer or as a heavily distorted tetrahedral Ti(III) complex bearing two germanide cluster ligands. Both compounds display donor-acceptor interactions between single Ge vertex atoms of the [Ge9] clusters and Ti(III). Compounds 1 and 2 were characterized by single-crystal X-ray diffraction, EPR spectroscopy, and elemental analysis.

Paramagnetic Prussian Blue Analogues CsM(II)[M(III)(CN)6]. The Quest for Spin on Cesium Ions by Use of (133)Cs MAS NMR Spectroscopy.

The (133)Cs magic-angle spinning NMR spectra of the paramagnetic compounds CsM(II)[M(III)(CN)6], M(II) = Ni, Co, Fe, Mn; M(II) = Co, Fe, yield unusually large and temperature-dependent signal shifts (up to -950 ppm relative to CsCl at 298 K). Comparison with the spectra of the diamagnetic analogues CsM[Co(CN)6], M = Zn, Cd, shows that the shifts are largely due to the unpaired electrons. This is ascribed to through-bond transfer of spin to the Cs(+) ions, while the through-space effect of the magnetic moments on the signal shifts is shown to be virtually negligible. The mechanism inducing negative spin at Cs(+) is discussed. The magnitude of the spin density (average: |5.8 × 10(-3)| (a.u.) (-3)) suggests that Cs(+) is involved in magnetic exchange interactions of corresponding Prussian blue derivatives.

The effect of Al-doping on ZnO nanoparticles applied as catalyst support.

A pure ZnO sample and a sample containing 3 mol% Al were prepared by (co)-precipitation as model materials for the oxidic support phase in Cu/ZnO/Al(2)O(3) methanol synthesis catalysts. The samples were characterized with respect to their crystal, defect and micro-structure using various methods (XRD, TEM, XPS, UV-vis spectroscopy, EPR, NMR). It was found that a significant fraction of the Al is incorporated into the ZnO lattice and enhances the defect chemistry of the material. The defect structure, however, was not stable under reducing conditions as applied in catalytic reactions. Al ions migrated towards the surface of the ZnO nanoparticles leading to formation of an Al-rich shell and an Al-depleted core. This process proceeds during the first 10-20 hours on stream and is associated with strong modification of the optical bandgap energy and the EPR signal of donor sites present in ZnO.

Copper(II) complexes incorporating poly/perfluorinated alkoxyaluminate-type weakly coordinating anions: syntheses, characterization and catalytic application in stereoselective olefin aziridination.

The synthesis and characterization of a series of cationic copper(II) complexes of the type [Cu(NCR)(6)][Al(OC(CF(3))(2)R')(4)](2) (R = CH(3), Ph; R' = CF(3), Ph, PhCH(3)), incorporating poly/perfluoronated alkoxyaluminates as weakly coordinating anions (WCAs) is presented. Aziridination of various olefins, such as the unreactive olefins e.g. ethylhex-2-enoate and 1-decene, with N-tosyliminophenyliodinane catalyzed by [Cu(NCR)(6)][Al(OC(CF(3))(2)R')(4)](2) affords very good yields (up to 96%) and high TOFs (up to 5000 h(-1)) under mild conditions. Using disubstituted olefins as substrates, high stereoselectivities are obtained at room temperature. The to date highest cis : trans ratio (98 : 2) of the obtained aziridines is achieved for cis-stilbene in good yield (85%) as well as promising TOF (> 2000 h(-1)). The investigation of the solvent effect on yield and selectivity reveals that for certain oleophilic substrates (1-decene), less polar solvents, such as dichloromethane are a better choice than acetonitrile, which is commonly considered as the best solvent for olefin aziridination. Accordingly, a mechanism involving a paramagnetic copper nitrene intermediate with both concerted and stepwise pathways is proposed.

Structure and bonding of [V(IV)O(acac)(2)] on the surface of AlF(3) as studied by pulsed electron nuclear double resonance and hyperfine sublevel correlation spectroscopy.

Well defined isolated [V(IV)O(acac)(2)] surface complexes have been prepared on aluminium trifluoride, alpha-AlF(3), as solid support by equilibrium adsorption from liquid solution. The paramagnetic vanadium(iv) surface complexes were studied by pulsed electron spin resonance spectroscopy in combination with quantum chemical calculations using density functional theory. (19)F and (27)Al ligand hyperfine interactions with the nuclei of the AlF(3) support observed by pulsed electron nuclear double resonance and hyperfine sublevel correlation spectroscopy experiments verify the direct chemical bonding between the vanadium and a surface fluorine atom. Detailed analysis of the ligand hyperfine couplings supported by quantum chemical calculations indicates that the axial position of [V(IV)O(acac)(2)]trans to the oxo ligand is bound directly to a terminal fluorine atom of the support. Analysis of the (1)H ligand hyperfine interaction revealed that an acidic H(+) of the AlF(3) surface protonated a donor oxygen of the acetylacetone ligand in the surface complex.

A Q- and X-band pulsed electron nuclear double resonance study of the structure and location of the vanadyl ions in the Cs salt of heteropolyacid PVMo11O40.

The location and coordination geometry of vanadium(IV) ions in the cesium salt of molybdovanadophosphoric heteropolyacid Cs(4)PVMo(11)O(40) were studied using orientation-selective pulsed ENDOR (electron nuclear double resonance) experiments. To enhance the orientation selectivity for the paramagnetic vanadyl species, these investigations were done at Q-band frequencies. It was possible to resolve interactions of the paramagnetic vanadyl ions (VO(2+)) with all relevant nuclei, (1)H, (31)P, (51)V, and (133)Cs. The location of the vanadyl species was studied by determination of the complete (31)P hyperfine tensor. This approach was done for both the fresh and the calcined Cs(4)PVMo(11)O(40) materials, and no differences in the structures of the VO(2+) complexes were found. The ENDOR results give experimental evidence for the location of the V(IV) ions. For both samples, it was possible to exclude the incorporation of V(IV) at the Mo sites. The VO(2+) species are directly attached to the outer surface of the heteropolyanion and coordinated to four of the outer oxygen atoms with a V-P distance of 3.96 A.