Synthesis and Characterization of Pentachlorophenyl–Metal Derivatives with d⁰ and d¹⁰ Electron Configurations

Abstract

By reaction of [TiCl(3)(thf)(3)] with LiC(6)Cl(5), the homoleptic organotitanium(III) derivative [Li(thf)(4)][Ti(III)(C(6)Cl(5))(4)] (1) has been prepared as a paramagnetic (d(1), S = 1/2, g(av) = 1.959(2)), extremely air-sensitive compound. Oxidation of 1 with [N(C(6)H(4)Br-4)(3)][SbCl(6)] gives the diamagnetic (d(0)) organotitanium(IV) species [Ti(IV)(C(6)Cl(5))(4)] (2). Compounds 1 and 2 are also electrochemically related (E(1/2) = 0.05 V). The homoleptic, diamagnetic (d(10)) compounds [N(PPh(3))(2)][Tl(C(6)Cl(5))(4)] (3) and [Sn(C(6)Cl(5))(4)] (4) have also been prepared. Nearly tetrahedral environments have been found for the d(0), d(10), and d(1) metal centers in the molecular structures of compounds 2-4 as well as in that of [Li(thf)(2)(OEt(2))(2)][Ti(III)(C(6)Cl(5))(4)].CH(2)Cl(2) (1') (X-ray diffraction). The reaction of the heavier Group 4 metal halides, MCl(4) (M = Zr, Hf) with LiC(6)Cl(5) in the presence of [NBu(4)]Br gives, in turn, the heteroleptic species [NBu(4)][M(C(6)Cl(5))(3)Cl(2)] (M = Zr (5), Hf (6)). Compounds 5 and 6 are isomorphous and isostructural, with the metal center in a trigonal-bipyramidal (TBPY-5) environment defined by two axial Cl ligands and three equatorial C(6)Cl(5) groups (X-ray diffraction). No redox features are observed for compounds 3-6 in CH(2)Cl(2) solution between -1.6 and +1.6 V.

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

“…clude that the documented ability of the C 6 Cl 5 group to enable the formation of homoleptic s-organyl derivatives in different oxidation states for a given metal (M = Ti, [14] V, Cr, [20] Rh [21] and Pt [30] ) relies more on the shielding effect exerted by the ortho-Cl substituents than on the groups electron-withdrawing properties. This would also explain the close relationship between the metal chemistries of the C 6 Cl 5 and the mesityl ligands, given that similar van der Waals volumes are ascribed to the Cl and CH 3 substituents (0.0195 and 0.0222 nm 3 , respectively).…”

“…Tetrasubstituted homoleptic compounds with different geometries have thus been prepared for the following series of metal centres: Ti IV /Ti III , [14] Cr IV /Cr III /Cr II , [20a] Rh III /Rh II [21] and Pt IV /Pt III /Pt II . [30] It therefore seemed advisable to study the redox behaviour of compounds 1-3 by electrochemical methods.…”

“…, [14] regardless of their different electron configurations. The local geometry around the V centre in 1' is also similar to that found in the neutral spe- …”

“…Two of these angles are smaller than the ideal tetrahedral value (109.58), while the remaining four are larger, thus resulting in a slight elongation of the tetrahedron. These angular distortions can reasonably be ascribed to the highly anisotropic character of the C 6 Cl 5 rings, a feature noticed earlier not only in related organometallic species, [14] but also in simple main-group ER 4 derivatives with various polyatomic, monodentate R substituents. [15] The small value of the T-4 shape measure [16] obtained for 1' (S(T-4) = 0.805 [17] ) denotes that the angular distortions around the vanadium centre are of minor importance.…”

“…Moderate swings in the C 6 Cl 5 rings had already been observed both in titanium and in main group nearly T-4 [M-(C 6 Cl 5 ) 4 ] qÀ compounds (q = 0, M = Ti, Sn; q = 1, M = Ti, Tl), and this feature was attributed to steric problems in the tetrahedral arrangement of these bulky ligands around the metal centre. [14] The [V III (C 6 [23] or tetrahedral sites in ZnS-like semiconductors (V III , g = 1.92-1.99). [24] Only recently has it been possible to obtain EPR spectra of the six-coordinate species [V(acac) 3 ], [VX 3 (thf) 3 ] (X= Cl, Br) and [V(OH 2 ) 6 ] 3 + by use of high-frequency techniques.…”