Highly efficient dehydrogenation of formic acid in aqueous solution catalysed by an easily available water-soluble iridium(iii) dihydride

Abstract

The new water-soluble cis-mer-[IrH2Cl(mtppms)3] (mtppms = monosulfonated triphenylphosphine) was employed as a catalyst for selective decomposition of formic acid to H2 + CO2 in aqueous solution at T = 30-100 °C. The easily synthesized compound showed high catalytic activity (TOF up to 298 000 h(-1)) and could be reused several times with no loss of activity (total TON = 67 650). A sharp maximum in the reaction rate was observed at pH = 3.75; its coincidence with the pKa of formic acid shows that both H(+) or HCOOH and HCOO(-) play important roles in the reaction mechanism.

Hidrogén tárolása homogén katalitikus kémiai rendszerekben

“…We have found that a similar, but water-soluble iridium(I) complex, cisz-mer-[IrH 2 Cl(mtppms-Na) 3 ], 7 (Fig. 4) was outstandingly active in FA decomposition; in fact it showed the third highest activity (TOF = 298 000 h -1 ) among the known homogeneous catalysts of this reaction 26 . High chemical stability of 7 is exemplified by the high turnover number (TON = 674 000) obtained in the presence of a large excess of formic acid.…”

“…Igen nagy katalitikus aktivitást észleltek ródium 17,18 , ruténium 19 és iridium 20 26 . 2 Cl(mtppms-Na) 3 ]-katalizálta bontásával -a hõmérséklet hatása.…”

“…100 °C hõmérsékleten TOF = 298 000 h -1 katalitikus frekvencia értéket határoztunk meg, ami szerint a cisz-mer-[IrH 2 Cl(mtppms-Na) 3 ] az oldható fémkomplexek között a harmadik legnagyobb aktivitású ismert katalizátor H 2 fejlesztéséhez hangyasav bontása révén. Kiváló a vegyület stabilitása is: egy 40 órás kísérletben 115 °C hõmérsékleten a katalitikus ciklusszám TON = 674 000 volt 26 . A katalizátor elsõsorban aktivitása és stabilitása miatt érdemel figyelmet, de lényeges szempont az elõállítás egyszerûsége is.…”

A novel carbohydrate labeling method utilizing transfer hydrogenation-mediated reductive amination

“…Since our earlier studies, using both [RuCl 2 (mtppms) 2 ] and [IrH 2 Cl(mtppms) 3 ], showed excellent catalytic activities in hydrogenation and transfer hydrogenation of various unsaturated groups [17,18] and in decomposition of formic acid [12], we envisaged their applicability in transfer hydrogenation of the imine intermediates of glycan labeling by reductive amination (Figure 1). Figure 3A.…”

“…To avoid the generation of the acutely toxic hydrogen cyanide, several substitutes were evaluated to replace the sodium cyanoborohydride as reductive agent. Figure 2) were made in house as described earlier in [12] and [13], respectively (Please note that the Ru(II)-complex has a dimeric structure in solid state as shown in Figure 2, however, for the sake of simplicity we refer to here as a monomer). Both complexes are highly water-soluble and can be synthesized easily from their halide precursors of IrCl 3 .3H 2 O [12] and RuCl 3 .3H 2 O [13], respectively, in reaction with monosulfonated triphenylphosphine (mtppms [13]).…”