Preparation and crystal structure of [WCl₂(cp)₂]⁺₂[W₄F₁₈]^2–(cp =η-C₅H₅) containing the new binary tungsten(IV) fluoride anion [W₄F₁₈]^2–

The Autoionization of [TiF4] by Cation Complexation with [15]Crown‐5 To Give [TiF2([15]crown‐5)][Ti4F18] Containing the Tetrahedral [Ti4F18]2− Ion

“…Examples include the autoionization of alkali metals M on reaction with crown ethers to give complexed M + as well as alkalides and electrides, [2] and the autoionization of main-group and transition-metal chlorides to give cationic crown ether complexes and metal chloro anions. [3] We report herein the reaction of TiF 4 and [15]crown-5 to give [TiF 2 ([15]crown-5)][Ti 4 F 18 ]·0.5 MeCN (1). This is, as far as we are aware, the first autoionization of a metal fluoride on reaction with a crown ether, and suggests that this is a viable preparative route to other related binary fluoro metal anions.…”

“…This is, as far as we are aware, the first autoionization of a metal fluoride on reaction with a crown ether, and suggests that this is a viable preparative route to other related binary fluoro metal anions. [Ti 4 2À cage (M = metal, X = halogen), the first being [W 4 F 18 ] 2À . [4] Its structure is related to the moreelaborate oxo complexes, for example, [Ti 4 F 12 O 6 ] 4À , [5] and [Ti 4 O 6 (OSMe 2 ) 12 ] 4+ .…”

“…[Ti 4 2À cage (M = metal, X = halogen), the first being [W 4 F 18 ] 2À . [4] Its structure is related to the moreelaborate oxo complexes, for example, [Ti 4 F 12 O 6 ] 4À , [5] and [Ti 4 O 6 (OSMe 2 ) 12 ] 4+ . [6] The related [Ti 2 F 9 ] À ion was claimed to exist in solution, [7] and the salts M[Ti 2 F 9 ] (M = Cs, NF 4 ) have been reported, [8] although their X-ray crystal structures were not determined.…”

“…[23] Consistent with the latter model, the F bridging ···F bridging contacts (2.596 (4) [10e] the F-Ti-F angles are determined by the almost equal nonbonding F···F distances, in a similar way to various second and third row main group fluorides. [23] To answer the question as to why [Ti 4 À ions is favored in the gas phase over dimerization to the [Ti 4 F 18 ] 2À ion. The situation is less clear for solutions in acetonitrile and dichloromethane, and most likely both anions exist in equilibrium.…”

“…The energetics in the solid state were estimated by using the equation of Jenkins et al and applying the "volume-based" thermodynamic (VBT) approach. [24,25] Dimerization to the [Ti 4 (6) and (7) for salts containing mono-and dications of different sizes were compared (Figure 2). The VBT approach suggests that the monocations generally favor the formation of [cation][Ti 2 F 9 ] (since DH(6) (% DG(6)) is usually > 0), whereas dications favor [cation]-[Ti 4 F 18 ] (since DH(7) (% DG(7)) < 0, i.e., negative and almost independent of the size of the cation).…”