New Homoleptic Organometallic Derivatives of Vanadium(III) and Vanadium(IV): Synthesis, Characterization, and Study of Their Electrochemical Behaviour

Abstract

The arylation of [VCl3(thf)3] with LiR(Cl), where R(Cl) is a polychlorinated phenyl group [C6Cl5, 2,4,6-trichlorophenyl(tcp), or 2,6-dichlorophenyl (dcp)] gives four-coordinate, homoleptic organovanadium(III) derivatives with the formula [Li(thf)(4)][V(III)(R(Cl))(4)] (R(Cl) = C(6)Cl(5) (1), tcp (2), dcp (3)). The anion [V(III)(C6Cl5)4]- has an almost tetrahedral geometry, as observed in the solid-state structure of [NBu4][V(C6Cl5)4] (1') (X-ray diffraction). Compounds 1-3 are electrochemically related to the neutral organovanadium(IV) species [V(IV)(R(Cl))4] (R(Cl) = C6Cl5 (4), tcp (5), dcp (6)). The redox potentials of the V(IV)/V(III) semisystems in CH2Cl2 decrease with decreasing chlorination of the phenyl ring (E(1/2) = 0.84 (4/1), 0.42 (5/2), 0.25 V (6/3)). All the [V(IV)(R(Cl))4] derivatives involved in these redox couples could also be prepared and isolated by chemical methods. The arylation of [VCl(3)(thf)(3)] with LiC6F5 also gives a homoleptic organovanadium(III) compound, but with a different stoichiometry: [NBu4]2[V(III)(C6F5)5] (7). In this five-coordinate species, the C6F5 groups define a trigonal bipyramidal environment for the vanadium atom (X-ray diffraction). EPR spectra for the new organovanadium compounds 1-6 are also given and analysed in terms of an elongated tetrahedral structure with C(2v) local symmetry. It is suggested that the R(Cl) groups exert a protective effect towards the vanadium centre.

Homoleptic Organoderivatives of High‐Valent Nickel(III)

“…This fact, together with the hard character of the C-donor atom and the marked electron-withdrawing nature of the C 6 X 5 groups, [39] made this approach particularly suitable for the species in question. The procedure has already been successfully applied to other related compounds containing metal centers with different electron configurations, such as V iii (d 2 ) [40] and…”

Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═CtBu2)4 (M = V, Nb, Ta)

“…41 This makes use of the fact that in the frozen solution spectra of these systems, only g ‖ and A ‖ can be easily determined (single-crystal studies can provide the full tensors for both g and A , as done by Kirmse et al . ), 42 but here, for 2 and especially 7 , the g ⊥ and A ⊥ values are relatively uncertain.…”

“…Using the relationships: $$g_{\mathit{\text{iso}}}=\frac{false(g_{\Vert }+2g_{\perp }false)}{3},a_{\mathit{\text{iso}}}=\frac{false(A_{\Vert }+2A_{\perp }false)}{3}$$ By substitution of Eqns 1 into Eqn 2b, and making use of Eqn 2a to substitute for g ‖ and g ⊥ , one obtains: $$a_{\mathit{\text{iso}}}=-Ptrue[\kappa +false(g_e-g_{\mathit{\text{iso}}}false)true]$$ Subtraction of Eqn 3 from Eqn 1a, and substituting for g ⊥ from Eqn 2a, gives: $$A_{\Vert }-a_{\mathit{\text{iso}}}=-Ptrue[\frac{4}{7}+\frac{11}{14}false(g_e-g_{\Vert }false)-\frac{5}{14}false(g_e-g_{\mathit{\text{iso}}}false)true]$$ allowing calculation of P in the system of interest; Eqn 3 then yields |κ|, since the sign of a iso is not known experimentally. This method, applied to [V(C 6 Cl 5 ) 4 ], gave | P | = 323 MHz, |κ| = 0.54, 41 and for [Nb(C 6 Cl 5 ) 4 ], gave | P | = 352 MHz, |κ| = 0.99. 46 This method had not been previously applied to V(Mes) 4 , yet this is among the most relevant complexes to ours and that for which the best EPR data are available.…”

Continuous Symmetry Analysis of NMR Chemical Shielding Anisotropy

“…The CSM methodology has been applied successfully to many symmetry related problems in physics, chemistry, biochemistry and spectroscopy, and some examples are collected in references [4,[12][13][14][15][16][17]. Of relevance to this report are the relationships between octahedricity or trigonal prismacity, and the magnetic moment within a family of related spin crossover complexes, which were found by Alvarez to be in- Figure 2.…”