1372665-07-0Relevant academic research and scientific papers
Investigations of the Magnetic and Spectroscopic Properties of V(III) and V(IV) Complexes
Van Stappen, Casey,Maganas, Dimitrios,Debeer, Serena,Bill, Eckhard,Neese, Frank
, p. 6421 - 6438 (2018)
Herein, we utilize a variety of physical methods including magnetometry (SQUID), electron paramagnetic resonance (EPR), and magnetic circular dichroism (MCD), in conjunction with high-level ab initio theory to probe both the ground and ligand-field excited electronic states of a series of V(IV) (S = 1/2) and V(III) (S = 1) molecular complexes. The ligand fields of the central metal ions are analyzed with the aid of ab initio ligand-field theory (AILFT), which allows for a chemically meaningful interpretation of multireference electronic structure calculations at the level of the complete-active-space self-consistent field with second-order N-electron valence perturbation theory. Our calculations are in good agreement with all experimentally investigated observables (magnetic properties, EPR, and MCD), making our extracted ligand-field theory parameters realistic. The ligand fields predicted by AILFT are further analyzed with conventional angular overlap parametrization, allowing the ligand field to be decomposed into individual σ- and π-donor contributions from individual ligands. The results demonstrate in VO2+ complexes that while the axial vanadium-oxo interaction dominates both the ground- and excited-state properties of vanadyl complexes, proximal coordination can significantly modulate the vanadyl bond covalency. Similarly, the electronic properties of V(III) complexes are particularly sensitive to the available σ and π interactions with the surrounding ligands. The results of this study demonstrate the power of AILFT-based analysis and provide the groundwork for the future analysis of vanadium centers in homogeneous and heterogeneous catalysts.
Bimetallic halides. Crystal structure of and ethylene polymerization by VCl2·ZnCl2·4THF
Smith, Paul D.,Martin, Joel L.,Huffman, John C.,Bansemer, Rick L.,Caulton, Kenneth G.
, p. 2997 - 3002 (2008/10/08)
The title compound is prepared either by the zinc reduction of VCl4(THF)2 in refluxing THF or by the reaction of [V2(μ-Cl)3-(THF)6]2Zn 2Cl6 with ZnCl2(THF)2 in THF at 90°C. The crystal structure indicates discrete molecules of (THF)4V(μ-Cl)2ZnCl2. The six-coordinate environment of vanadium approximates octahedral geometry whereas the four-coordinate zinc geometry is virtually tetrahedral. The octahedron and tetrahedron are linked by two chloride bridges. Crystals belong to the monoclinic space group P21/c with cell dimensions (-158°C) a = 14.732 (5) A?, b = 9.680 (3) A?, c = 16.207 (6) A?, and β = 94.12 (2)° and Z = 4. High catalytic activity was found for ethylene polymerization by the title compound as well as for several other related V/Zn/Cl/THF compounds whose structures have been established. Catalyst activity is greatly enhanced by added halocarbons. Activity of V(II) compounds equals or exceeds that of V(III) compounds, which tends to deny a previous suggestion that the halocarbon functions to keep vanadium in oxidation state +3. Moreover, the V(II) compounds fail to be oxidized to V(III) even by neat CH2Cl2.
