Johann Spandl

Ion chemistry of the hexanuclear methoxo-oxovanadium cluster V6O7(OCH3)12

Abstract The hexanuclear methoxo-oxovanadium cluster V6O7(OCH3)12 (1) is investigated by electrospray ionization in methanol solution. Collision experiments unravel the fragmentation schemes of the molecular ions 1+ and 1− as well as the H+, Na+, and Cs+ adducts of 1. In general, fragmentation of the hexanuclear cluster ions commences with sequential expulsions of two OV(OCH3)3 units to yield the corresponding V4 clusters. However, when an active proton is present in the cluster ion, e.g., in the protonated molecule [ 1 + H ]+, loss of methanol precedes degradation to V4 clusters. In addition, the experiments suggest that electrospray ionization provides as an alternative method for the generation of metal oxide cluster ions VmOn+/− (m=1–4, n=0–11).

Solvothermal Synthesis of a 24-Nuclear, Cube-Shaped Squarato-oxovanadium(IV) Framework: [N(nBu)4]8[V24O24(C4O4)12(OCH3)32]

Polydentate bridging ligands can be used to link small polyoxo-alkoxo-metalate units to form supramolecular clusters. In the title compound, twelve μ4 -bridging squarato groups connect eight trinuclear methoxo-oxo-vanadate units to form a tetradodecanuclear cubic framework, in whose cavity six n-butyl groups of the tetra-n-butylammonium cations are anchored.

[Fe19 ] "Super-Lindqvist" Aggregate and Large 3D Interpenetrating Coordination Polymer from Solvothermal Reactions of [Fe2 (OtBu)6 ] with Ethanol.

The syntheses, crystal structures, and physical properties of [HFe19 O14 (OEt)30 ] and {Fe11 (OEt)24 }∞ are reported. [HFe19 O14 (OEt)30 ] has an octahedral shape. Its core with a central Fe metal ion surrounded by six μ6 -oxo ligands is arranged in the rock salt structure. {Fe11 (OEt)24 }∞ is a mixed-valence coordination polymer in which Fe(III) metal ions form three 3D interpenetrating (10,3)-b nets. The arrangement of the Fe(III) ions can also be compared to that of Si ions in α-ThSi2 . Thus, the described structures are at the interface between molecular and solid-state chemistry.

Hexafluoridotechnetate(IV) revisited.

Novel synthetic routes to hexafluoridotechnetate(IV) are reported, and for the first time the single-crystal X-ray structures of several M2[TcF6] salts (M = Na, K, Rb, Cs, NH4, and NMe4) were determined. The ammonium and the alkaline metal salts crystallize in the trigonal space group P3m, while the NMe4(+) salt belongs to the space group R3. [TcF6](2-) salts are widely stable in aqueous solution. In alkaline media, however, a slow hydrolysis is observed, and the first hydrolysis product, the dimeric, oxido-bridged complex [F5Tc-O-TcF5](4-), could be studied structurally.

Versatile Organic Chemistry on Vanadium-Based Multi-Electron Reservoirs

We report the synthesis, post-functionalization, and redox behavior of two organically functionalized aggregates, [V6 O7 (OMe)9 {(OCH2 )3 C-CH2 N3 }] and [V6 O7 (OMe)9 {(OCH2 )3 C-NH2 }]. All twelve μ2 -oxo groups on the edges of the Lindqvist-type {V6 O19 } core were replaced by alkoxo ligands. The absence of a negative charge and the closed organic shell make these neutral mixed-valence compounds very stable towards hydrolysis and well soluble in almost all common organic solvents. These are important advantages over classical POMs. By post-functionalization through copper(I)-catalyzed Huisgen cycloaddition or imine formation, various organic moieties could be introduced. Even a well-soluble trimer composed of three hexanuclear vanadium units connected through an aromatic triimino core was synthesized and studied. The diverse redox behavior, the versatile reactivity, the good stability, and the excellent solubility make our vanadium compounds highly interesting for applications as building blocks in macromolecular chemistry as well as redox labels in biochemistry.