The chemistry and preparation of tantalum complexes with 2,3-dihydroxy benzoic acid: Experimental and theoretical investigation

Peroxotantalate‐Based Ionic Liquid Catalyzed Epoxidation of Allylic Alcohols with Hydrogen Peroxide

“…It was observed that [P 4,4,4,4 ]Br displayed as trong band at 921 cm À1 and aw eaker band at 905 cm À1 ( Figure 1A(a)), whereas ILs exhibited only as trong band around 905 cm À1 and the band at 921 cm À1 disappeared, which might result from the vibration of n as [Ta=O] in the ILs despite the overlap with that of the organic cation part (Figure 1A). [8,23] Raman spectroscopy gave as imilarr esult, as shown in Figure 1B.T he Ramans hift of the tetraperoxometalate compound (NH 4 ) 3 [Ta(O 2 ) 4 ]s howedt he band near 550 cm À1 ,w hich correspondedt ot he vibration n s [Ta(O 2 )],a nd the band around 830 cm À1 was assigned to the n(OÀO) ( Figure 1B(b)). [9a] Similarly,f or the ILs ( Figure 1B (c, d, e)), the band near 550 cm À1 was associated with the vibration n s [Ta(O 2 )],a nd the band around 838 cm À1 was for the n(OÀO).…”

“…[4] However, the tungsten-basedc atalysts usually exist in the form of polynuclear speciesa nd might have limited turnover frequency. [8] These complexes correspond eithert oh omoleptic tetraperoxotantalates of the general formula (M) 3 [Ta(O 2 ) 4 ]( M= K + ,N H 4 + ,N a + and gu + )o rt oh eteroleptic peroxo-carboxylate compounds, such as (M) 3 [Ta(O 2 ) 3 (L)]·x H 2 O, where Li st artrate, citrate, o-phenanthroline, oxalic acid, catechol, carboxylic acid, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), or acetylacetone (acac), etc. [6] Nevertheless, niobium or tantalum-based catalysts have been rarely employed for catalytic oxidation.…”

“…It has been reported that tantalum peroxoc omplexes are potential oxygen donors to organic substratesi nt he reactionm edium. [8] These complexes correspond eithert oh omoleptic tetraperoxotantalates of the general formula (M) 3 [Ta(O 2 ) 4 ]( M= K + ,N H 4 + ,N a + and gu + )o rt oh eteroleptic peroxo-carboxylate compounds, such as (M) 3 [Ta(O 2 ) 3 (L)]·x H 2 O, where Li st artrate, citrate, o-phenanthroline, oxalic acid, catechol, carboxylic acid, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), or acetylacetone (acac), etc. [9] Additionally,t he dimeric tantalump eroxo complex and heterobimetallic tantalum peroxoc omplex have also been prepared and characterized from the structural and spectroscopic point of view,b ut their catalyticp erformance for epoxidation has rarely been explored.…”

“…There are very limited studies about tantalum‐based catalysts in the epoxidation reaction. It has been reported that tantalum peroxo complexes are potential oxygen donors to organic substrates in the reaction medium . These complexes correspond either to homoleptic tetraperoxotantalates of the general formula (M) 3 [Ta(O 2 ) 4 ] (M=K + , NH 4 + , Na + and gu + ) or to heteroleptic peroxo‐carboxylate compounds, such as (M) 3 [Ta(O 2 ) 3 (L)] ⋅ x H 2 O, where L is tartrate, citrate, o ‐phenanthroline, oxalic acid, catechol, carboxylic acid, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), or acetylacetone (acac), etc .…”

A combined experimental and theoretical analysis on molecular structure and vibrational spectra of 2,4-dihydroxybenzoic acid

“…To the best of our knowledge, no detailed study on vibrational spectra for 2,4-DHBA has been reported up to now. Literature survey shows that the vibrational assignments for the similar molecule like 2,3-dihydroxybenzoic acid [11] and 4-dihydroxybenzoic acid [12] have been made. However, the position of hydroxyl groups and the hydrogen bonds strongly affect the vibrational spectra, the highly accurate calculations on the structure of 2,4-DHBA and the detailed assignment on its vibrational bands are still desired.…”