Non-aqueous synthetic methodology for TiW5 polyoxometalates: protonolysis of [(MeO)TiW5O18]3– with alcohols, water and phenols

Abstract

The tetra-n-butylammonium (TBA) salt of [(MeO)TiW(5)O(18)](3-) 1 was reacted with alcohols ROH to give primary, secondary and tertiary alkoxide derivatives [(RO)TiW(5)O(18)](3-) (R = Et 2, (i)Pr 3 and (t)Bu 4), whilst hydrolysis afforded [(mu-O)(TiW(5)O(18))(2)](6-) 5 rather than the hydroxo derivative (R = H). In reactions with (i)PrOH and (t)BuOH, impurity peaks observed at 1015 and 1020 ppm in the (17)O NMR spectra indicate alkoxide degradation and Ti=O bond formation via reactions analogous to those occurring at the surfaces of solid heteropolyacids. Aryloxides [(ArO)TiW(5)O(18)](3-) were prepared by reacting 1 with phenols ArOH (Ar = C(6)H(5) 6, C(6)H(4)Me-4 7, C(6)H(4)(t)Bu-4 8, C(6)H(4)OH-4 9, C(6)H(4)OH-3 10, C(6)H(3)(OH)(2)-3,5 11 and C(6)H(4)CHO-2 13). TiW(5)O(18) units were linked by reacting 1 with 9 to give [(mu-1,4-OC(6)H(4)O)(TiW(5)O(18))(2)](6-) 12. (17)O and (183)W NMR spectra are reported and X-ray crystal structures were obtained for TBA salts of anions 3-10 and 13, which showed that the titanium is six-coordinate in all cases. Reactions were monitored by (1)H NMR, including a 2D-EXSY study of methoxo exchange, and the slow rates observed are probably associated with the reluctance of titanium in these anions to achieve seven-coordination.

Coordination-Induced Condensation of [Ta6O19]8–: Synthesis and Structure of [{(C6H6)Ru}2Ta6O19]4–and [{(C6H6)RuTa6O18}2(μ-O)]10−

“…O 18 ] showed the reaction to be remarkably slow and require long heating times. 29 Aqueous Speciation of Na 4 -2. The 13 C NMR spectrum of for 2 h, but no changes were detected, indicating that the cis/ trans ratio is not appreciably temperature dependent.…”

A Quantum Chemical Study of the Structure, Bonding Characteristics and Nonlinear Optical Properties of Aryloxido and Salicylaldehydo Derivatives of [XW5O18]3– (X = Zr or Ti)

“…The optimized partial geometrical parameters are listed in Table 1, which also includes experimental data. [21,22] Clearly, the important structural parameters are well-reproduced by the theoretical calculations. This suggests that our adopted method and basis sets are reliable for the systems studied.…”

“…[28,29] The geometries of all systems were optimized and the initial geometric data were obtained from the crystal data. [21,22] The local density approximation (LDA) characterized by the Vosko-WilkNusair (VWN) [30] parametrization for correlation was used. The generalized-gradient approximation (GGA) was employed in the geometry optimizations by using the Beck [30,31] and Perdew [32] exchange-correlation (XC) functional.…”

“…[22] The POM structures in these newly synthesized complexes are group 4 metal-substituted Lindqvist-type polytungstate anions [XW 5 O 18 ] 3-(X = Zr or Ti). The organic ligand is connected to the heteropolyanion cluster via linkage oxygen atoms (O L ).…”

Quantum Chemical Design for Enhanced Second‐Order NLO Response of Terpyridine‐Substituted Hexamolybdates

“…Firstly, they offer a wide range of metals with different coordination states and various organic groups which possess large π-conjugated systems. [27][28][29] Secondly, many of these compounds are known to possess intense low-lying electronic transitions. [22] Last but not least, POMs have been found to be extremely flexible building blocks as the non-centrosymmetric molecular structures can be achieved easily for such compounds.…”