Quantitative oxidation of organovanadium(IV) and -niobium(IV) complexes: synthesis of Cp2V(SbF6)2, [Cp2VCl2][AsF6], and [Cp2V(AsF6)2][AsF6]. Crystal structure of [Cp2NbCl2][SbF6]

Abstract

Quantitative Oxidation of Organovanadium( I V ) and -niobium( I V ) Complexes: Synthesis of cp2v( SbF,)*, [ cp2Vc12][ A#,], and [ Cp2V(ASF&][ ASF,]. Crystal Structure of [ Cp2NbC12][ SbF6]Niobocene dichloride, Cp,NbC12 (l), reacts with SbF, to give [Cp2NbC12] [SbF6] (2). The X-ray structure of 2 has been determined and shows 2 to consist to discrete SbF, anions, which show the usual octahedral geometry but are slightly disordered in the crystal, and CpZNbCl2+ cations with an approximate tetrahedral coordination of the Nb atom. The average Nb-Cl distance is 2.341 A; the Nb-C distances range from 2.354 to 2.455 A with an average of 2.404 A. The mean distance from Nb to the Cp ring centroids is 2.087 A.The angle C1-Nb-Cl is 98.10'; the average of the centroid-Nb-C1 angles is 106', the angle at Nb between the centroids 131°, and the angle between the ring planes 51.4'. 2 crystallizes in the orthorhombic space group mlcn with cell constants a = 8.557 (3) A, b = 12.753 (4) A, c = 13.839 (6) A, V = 1510.2 A3, 2 = 4, and R(F) = 3.3%. The oxidation of vanadocene dichloride, Cp2VClz (3), which is not possible by common agents such as Ag+, with AsF, has been estimated to be thermodynamically favored by simple Born-Haber cycles and has been proved to be a convenient and quantitative synthesis of novel organovanadium(V) species. [Cp2VC12] [AsF,] (5) and [Cp2V(AsF,),] [A#,] (6) were prepared and characterized by elemental analysis, IR, 'H NMR, and l9F NMR spectroscopy (5: 6 = -58.75 ppm, q; relative to CFC1,; J = 937 f 5 Hz). The preparation and characterization of the paramagnetic Cp,V(SbF6), (4) is also reported. The EPR spectrum of 4 shows a nicely resolved eight-line spectrum (B = 1.9738), indicating that the unpaired electron is mainly localized at the V.

Chemical Redox Agents for Organometallic Chemistry

“…161 162 The pentafluorides, EF 5 , are more difficult to handle (in part because of the formation of HF with water) but are stronger oxidants than the chlorides (SbF 5 will oxidize the less electron-rich triarylamines unaffected by SbCl 5 , section II.A.2.a.iii) and are less likely to give rise to halogenated byproducts. Accordingly, distillation of EF 5 (E ) As and Sb) onto solutions of [MX 2 Cp 2 ] (X ) Cl, M ) V, 163,164 ] and AgCl, i.e., that chloride abstraction occurs with Ag + even though oxidation is favored, and observed, with AsF 5 . 164 Moreover, the reaction between [ReCl 2 -Cp 2 ]Cl with a mixture of Ag[SbF 6 ] and SbF 5 gives [ReCl 2 Cp 2 ][SbF 6 ] 3 via abstraction of the chloride counteranion with Ag + and oxidation by the pentafluoride.…”

“…Accordingly, distillation of EF 5 (E ) As and Sb) onto solutions of [MX 2 Cp 2 ] (X ) Cl, M ) V, 163,164 ] and AgCl, i.e., that chloride abstraction occurs with Ag + even though oxidation is favored, and observed, with AsF 5 . 164 Moreover, the reaction between [ReCl 2 -Cp 2 ]Cl with a mixture of Ag[SbF 6 ] and SbF 5 gives [ReCl 2 Cp 2 ][SbF 6 ] 3 via abstraction of the chloride counteranion with Ag + and oxidation by the pentafluoride. 167 b. Nitrosonium, [NO] + , Salts.…”

Non-Traditional Oxidants in Preparative Coordination Chemistry

“…158 Reaction of |NbCl2Cp2] with SbFs in liquid SQ2 yields the oxidation product, [NbCl2Cp2][SbF6l and SbF3. 159 In the same report, oxidation of [VCI2CP2] by AsFs with the formation of [VCl2Cp2][AsF6] was described.…”

Reaction of [Ti(cp)2(AsF6)2](cp =η-C5H5) toward S4N4and Se4N4: identification in solution of [Ti(cp)2(S4N4)][AsF6]2; synthesis and characterization of [Ti(cp)2F(AsF6)], [Ti(cp)2F2]·AsF3and [Ti(cp)F3]·AsF3

“…The complex [Ti(cp),(AsF,),] 2, prepared from [Ti(cp),F,] 1 (cp = q-C,H,) and AsF,, was the first structurally characterized metallocene hexafluoroarsenate complex containing a direct M F E interaction (E = P, As, Sb or Bi).' It fertilized both the high-oxidation-state organometallic chemistry of the early transition elements [2][3][4] and the chemistry of cationic metallocene species containing co-ordinated neutral Lewis bases.' As the Ad?, unit in 2 can, owing to the high stability of the AsF,-anion, be displaced easily even by weak Lewis bases and poor electron donors, we became interested in the reactivity of complex 2 towards tetrachalcogen tetranitrides.…”

“…were identified ('H NMR spectroscopy) as it forms a stable adduct with AsF, yielding the hitherto unknown species [Ti(cp),F,].AsF, 7 [equation(2)] (see below). According to 1 + AsF, -[Ti(cp),F,]*AsF, (2) 7 equation (l), compound 2 acts as an oxidizing agent owing to the formation of AsF, (intermediate).…”