Syntheses, Characterizations, and X-ray Structures of Alkali Metal Derivatives of Titanium(IV) Neopentoxides

Abstract

Reactions of titanium(IV) neopentoxide, [Ti(μ-Oneo-Pe)(Oneo-Pe)3]2 (1, Oneo-Pe = OCH2CMe3), with alkali neopentoxides (AOneo-Pe) resulted in the isolation of the dimeric complexes [ATi(Oneo-Pe)5]2 [A = Li (2), Na (3), and K (4)], independent of the alkali metal investigated. Each compound was characterized by solution and solid-state multinuclear NMR, isopiestic molecular weight determination, and/or single-crystal X-ray diffraction. In the solid state, both 2 and 4 were found to adopt a standard [MM‘(OR)5]2 arrangement, wherein the Ti metals are in a distorted trigonal-bipyramidal geometry and each alkali metal center is four-coordinated. Suitable crystals of 3 were not isolated, but solid-state MAS (17O, 13C, x A) NMR spectroscopy indicated that the solid-state structure of 3 was consistent with its congeners. Multinuclear (1H, 7Li, 13C, 17O, 23Na) solution NMR spectroscopy data in toluene revealed that 2 exists in a complex multinuclear equilibrium, whereas 3 and 4 exist as mononuclear species in solution.

Vanadium-lithium alkoxides: synthesis, structure, spectroscopic characterisation and accidental degradation of silicone grease

“…Common experimental parameters were field modulation amplitude of 0.01 mT, conversion time of 40.96 ms per point, and time constant of 81.92 ms. All EPR spectra simulations were carried out with the EasySpin software Figure 1. R e p r e s e n t a t i o n o f t h e m o l e c u l a r s t r u c t u r e o f [V 2 (μ-ONep) 2 (ONep) 6 ], Nep = neopentyl, employed as starting material for the synthesis of complexes 1 and 2. 15 Thermal ellipsoids are drawn at the 50% probability level.…”

“…15 The system has shown high reactivity towards the silicone grease used in ground glass joints, and two very different products were isolated, [V 6 Li 10 16,17 however, to our knowledge, this has not been reported before for vanadium systems. The products are promising precursors for mixed metal oxides with vanadium in the +III/+IV oxidation states and, in the case of 1, also for V/Si/Li-containing composites.…”

“…614 neopentyl (Nep) groups, to develop new starting materials, in analogy to those described for titanium (IV). 6 Although the preparation of the first non-oxo vanadium(IV) alkoxides was reported as early as in the 1950s, 7 the reactivity and the structural patterns of these compounds are not well established and it was only recently that a {V(OR) 4 } n species was used in the preparation of mixed-metal aggregates. 8 The synthesis of heterometal alkoxo species is highly dependent upon the tendency of alkoxides or other ligands, such as halides, to bridge.…”

“…This work describes the facile 1:1 reaction between "Li(ONep)" 14 and [V 2 (μ-ONep) 2 (ONep) 6 ] ( Figure 1). 15 The system has shown high reactivity towards the silicone grease used in ground glass joints, and two very different products were isolated, [V 6 Li 10 16,17 however, to our knowledge, this has not been reported before for vanadium systems.…”

“…The average values for the Si-C and Si-O distances in the {OSi (Me) 6 ] starting materials (R = isopropyl or neopentyl) and other, more ionic alkali metal alkoxides (Na, K), where no product of silicone grease degradation has ever been isolated, even in thf solution. This suggests that the significant polarizing character of the lithium cation is relevant for the generation and stabilization of reaction intermediates in these systems.…”