131063-11-1Relevant articles and documents
Novel vanadium complexes supported by a bulky tris(pyrazolyl)borate ligand
Petrov, Pavel A.,Smolentsev, Anton I.,Bogomyakov, Artem S.,Konchenko, Sergey N.
, p. 60 - 64 (2017)
The V(III) complex [V(TptBu2)Cl2] (1, TptBu2?=?hydrotris(3,5-di-tert-butylpyrazolyl)borate) was synthesized by the reaction of [VCl3(THF)3] (prepared in situ) and K(TptBu2). Reduction of 1 with potassium mirror afforded the V(II) complex [V(TptBu2)Cl] (2). Both complexes were characterized by means of a single crystal X-ray diffraction. 1 represents the first example of pentacoordinated vanadium tris(pyrazolyl)borate (Tp) complexes. The V(III) ion environment is a distorted trigonal bipyramid. 2 is the first V(II) Tp-complex. The V(II) ion has tetrahedral environment, and the Cl atom is deviated from the B–V axis (∠B(1)–V(1)–Cl(1)?=?157.8°). Magnetic susceptibility measurements showed reasonable μeff values at 300?K: 2.80 (1) and 3.78 (2) μB, those prove the oxidation states of V: +3 (1) and +2 (2).
Non-Oxido-Vanadium(IV) Metalloradical Complexes with Bidentate 1,2-Dithienylethene Ligands: Observation of Reversible Cyclization of the Ligand Scaffold in Solution
Fugel, Malte,Grabowsky, Simon,Harmer, Jeffrey R.,Kleemiss, Florian,Lork, Enno,Schlüter, Dirk,Sugimoto, Kunihisa,Vogt, Matthias
, p. 1335 - 1343 (2020)
Derivatives of 1,2-dithienylethene (DTE) have superb photochromic properties due to an efficient reversible photocyclization reaction of their hexatriene structure and, thus, have application potential in materials for optoelectronics and (multi-responsive) molecular switches. Transition-metal complexes bearing switchable DTE motifs commonly incorporate their coordination site rather distant from the hexatriene system. In this work the redox active ligand 1,2-bis(2,5-dimethylthiophen-3-yl)ethane-1,2-dione is described, which reacts with [V(TMEDA)2Cl2] to give a rare non-oxido vanadium(IV) species 3(M,M/P,P). This blue complex has two bidentate en-diolato ligands which chelate the VIV center and give rise to two five-membered metallacycles with the adjacent hexatriene DTE backbone bearing axial chirality. Upon irradiation with UVA light or prolonged heating in solution, the blue compound 3(M,M/P,P) converts into the purple atropisomer 4(para,M/para,P). Both complexes were isolated and structurally characterized by single-crystal X-ray diffraction analysis (using lab source and synchrotron radiation). The antiparallel configuration (M or P helicity) present in both 3(M,M/P,P) and 4(para,M/para,P) is a prerequisite for (reversible) 6π cyclization reactions. A CW EPR spectroscopic study reveals the metalloradical character for 3(M,M/P,P) and 4(para,M/para,P) and indicates dynamic reversible cyclization of the DTE backbone in complex 3(M,M/P,P) at ambient temperature in solution.
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
supporting information, p. 6421 - 6438 (2018/06/14)
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.
