Synthesis and characterization of metal-substituted tetraalkylphosphonium polyoxometalate ionic liquids

Abstract

Trihexyl(tetradecyl)phosphonium and Keggin polyoxotungstates [PW11O39M(H2O)]n−, M = Fe, Co, Mn, or related lacunary [PW11O39]7− and [P2W20O70(H2O)2]10− anions yield compounds that are liquids at room temperature.

Physical and Electrochemical Modulation of Polyoxometalate Ionic Liquids via Organic Functionalization

“…In the case of the hybrid analogues, however, it was necessary to first isolate the hybridized cluster as either a tetra‐ N ‐butylammonium, ([TBA] + ) or potassium salt, to ensure that minimal free ligand or other side products would be incorporated into the resulting IL. The siloxane hybrid POM‐IL (THTP) 3 [PW 11 O 39 (SiPh) 2 O] ( 1 ) (where Ph=–C 6 H 5 ) was first synthesized using a modified literature procedure, in which two equivalents of trichlorophenylsilane were grafted directly onto the lacunary [PW 11 O 39 ] 7– cluster to yield (TBA) 3 [PW 11 O 39 (SiPh) 2 O] (TBA‐ 1 ). Cation exchange was performed under biphasic conditions (3:2 v/v water/cyclohexane) at 80 °C with an excess of trihexyltetradecylphosphonium chloride to yield 1 .…”

Synthesis, Physical Properties and Application of a Series of New Polyoxometalate-Based Ionic Liquids

“…As shown by Yan and coworkers [ 56 , 57 , 58 ] when comparing the melting points of (( n -C 10 H 21 )( n -C 4 H 9 ) 3 N + ) 5 [SiW 11 VO 40 ] (+95 °C) and (( n -C 14 H 27 )( n -C 4 H 9 ) 3 P + ) 5 [SiW 11 VO 40 ] (+50 °C), the choice of phosphonium cations instead of ammonium favors the decrease of the fusion temperature. In addition, the pioneering work of Rickert [ 59 , 60 ] and the more recent study of Nogueira [ 61 ] evidence that the trihexyltetradecylphosphonium cation leads to POM-ILs displaying melting points below room temperature. This is a required parameter to use such materials as solvent in oxidation reactions with soft conditions.…”

“…It is interesting to note that when the charge increases, we observe a tendency of the POM to interact with more cations. It was not reported so far with alkylammonium salts or with phosphonium-based POM-ILs for which the examples reported in the literature include POM with charges ranging only from 2 − to 5 − [ 56 , 57 , 58 , 59 , 60 , 61 ]. This phenomenon is particularly important with [SiW 10 O 36 ] 8− and was also observed for [PW 11 O 39 ] 7− and [P 8 W 48 O 184 ] 40− (unpublished results).…”

Designing Functional Polyoxometalate‐Based Ionic Liquid Crystals and Ionic Liquids

“…During the same period Thangadurai and Tong [115] [117][118][119][120][121][122] Most of them revealed low melting point POM-IL and found applications for depollution, presents a typical glass transition temperature of -24.6 °C, [123] while TOA + salts of [PW 11 O 39 M(H 2 O)] 4-/5-(M = Mn, Fe, Co, Ni, Cu, Zn) obtained by Shakeela et al [124] displayed melting points in the range 87-108 °C. Table 2 tries to gather an exhaustive list of true POM-ILs identified in the literature.…”