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Palladium nanoparticles stabilised by aniline modified polymer immobilised ionic liquid is a remarkably active catalyst for the hydrogenation of CO2 to formate; the initial TOF of 500 h−1 is markedly higher than either unmodified catalyst or its benzylamine and N,N-dimethylaniline modified counterparts and is among the highest to be reported for a PdNP-based catalyst. [ABSTRACT FROM AUTHOR]

RuNPs stabilised by amino‐decorated imidazolium‐based polymer immobilized ionic liquids catalyse the dimethylamine borane mediated reduction of quinolines to 1,2‐dihydroquinoline (DHQ) and 1,2,3,4‐tetrahydroquinoline (THQ). Partial reduction of 3‐substituted quinolines to the corresponding 1,2‐dihydroquinoline was achieved with 100 % selectivity in toluene under mild conditions. This is the first report of the selective partial reduction of 3‐substituted quinolines to the corresponding 1,2‐dihydroquinolines with a heterogeneous nanoparticle‐based catalyst. A wide range of substituted quinolines have also been reduced to the corresponding 1,2,3,4‐tetrahydroquinoline with high selectivity and good yields by adjusting the reaction time. The 1,2‐dihydroquinolines readily release dihydrogen in toluene at 60 °C in the absence of catalyst with no evidence for disproportionation and as such are potential organo‐hydride reagents. The initial TOF of 610 mol quinoline converted mol Ru−1 h−1 for the reduction of quinoline is among the highest to be reported for a metal nanoparticle‐based catalyst and the conversion of 96 % obtained after 4 h at 65 °C is significantly higher than its platinum nanoparticle counterpart PtNP@NH2‐PEGPIILS as well as 5 wt/% Ru/C, which only reached 9 % and 11 % conversion, respectively, at the same time. Hot filtration experiments showed that the active species was heterogeneous. [ABSTRACT FROM AUTHOR]

Bimetallic Ru:Co nanoparticles stabilized by PEG and imidazolium ionic liquid based [KIT-6] mesoporous silica, denoted as Ru:Co NPs@[KIT-6]-PEG&imid 6, has been synthetized by post grafting method and fully characterized by SEM, TEM, XPS, FT-IR and solid-state 13C and 29Si NMR spectroscopy. The supported Ru:Co mesoporous nanoparticles catalyst 6 revealed excellent catalytic activity (conversions up to 100%), turnover number (TON) of 770 and turnover frequency (TOF) of 7700 h−1 in the Suzuki–Miyaura cross-coupling of p-bromobenzonitrile and phenylboronic acid in H2O:EtOH (1:1) solution under very mild reaction conditions. In addition, the heterogeneous catalyst 6 maintains almost its inherent catalytic activity after the 6th catalytic recycle. [ABSTRACT FROM AUTHOR]

Abstract: Palladium nanoparticles stabilized by heteroatom donor‐modified polystyrene‐based polymer immobilized ionic liquids (PdNP@HAD‐PIILP; HAD‐PPh2, OMe, NH2, CN, pyrrolidone) are highly efficient catalysts for the Suzuki‐Miyaura cross‐coupling in aqueous media under mild conditions. Catalyst modified with phosphine was consistently the most efficient as it gave high yields across a range of substrates under mild conditions at low catalyst loadings. Incorporation of polyethylene glycol into the phosphine modified immobilised ionic liquid support improved catalyst efficacy by improving dispersibility and facilitating access to the active site. Moreover, each of the heteroatom modified catalysts was more active than the corresponding unsubstituted imidazolium‐based polystyrene benchmark as well as commercial samples of Pd/C. Catalyst generated in situ from either [PdCl4]@PPh2‐PIILP or its PEGylated counterpart [PdCl4]@PPh2‐PEGPIILP, by reduction with phenylboronic acid, outperformed their pre‐formed counterparts for the vast majority of substrates examined. The turnover frequency of 16,300 h−1 obtained at room temperature is one of the highest to be reported for palladium nanoparticle‐catalysed Suzuki‐Miyaura cross‐coupling between 4‐bromoacetophenone and phenylboronic acid in aqueous media under such mild conditions. [ABSTRACT FROM AUTHOR]

The asymmetric Diels-Alder reaction between N-acryloyloxazolidinone and cyclopentadiene and the Mukaiyama-aldol reaction between methylpyruvate and 1-phenyl-1-trimethylsilyloxyethene have been catalysed by heterogeneous copper(II)-bis(oxazoline)-based polymer immobilised ionic liquid phase (PIILP) systems generated from a range of linear and cross linked ionic polymers. In both reactions selectivity and ee were strongly influenced by the choice of polymer. A comparison of the performance of a range of Cu(II)-bis(oxazoline)-PIILP catalyst systems against analogous supported ionic liquid phase (SILP) heterogeneous catalysts as well as their homogeneous counterparts has been undertaken and their relative merits evaluated. [ABSTRACT FROM AUTHOR]

A linear cation-decorated polymeric support with tuneable surface properties and microstructure has been prepared by ring-opening metathesis polymerisation (ROMP) of a pyrrolidinium-functionalised norbornene-based monomer with cyclooctene. The derived peroxophosphotungstate-based polymer-immobilised ionic liquid phase (PIILP) catalyst is an efficient and recyclable system for the epoxidation of allylic alcohols and alkenes, with only a minor reduction in performance on successive cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrafine RuNPs stabilised by a phosphine oxide-modified polymer immobilized ionic liquid. • Complete selectivity for the partial reduction of aromatic and heteroaromatic nitroarenes to the corresponding N -arylhydroxylamine. • Highest initial turn over frequency to be reported for a RuNP catalysed partial reduction of nitrobenzene to N -phenylhydroxylamine. • Reduction of electron rich amino nitroarenes to the aniline proposed to occur via a quinondiimine-derived iminium. • High activity and selectivity retained over five reuses with only a minor reduction in conversion. RuNPs stabilised by a polymer immobilised ionic liquid derived from co-polymerisation of a PEG-substituted imidazolium-based styrene monomer and diphenyl(4-vinylphenyl)phosphine oxide, RuNP@O = PPh 2 -PEGPIILS, (2) is a remarkably efficient and selective catalyst for the hydrazine hydrate-mediated partial reduction of nitroarenes to the corresponding N -arylhydoxylamine. Near quantitative conversion to N -phenylhydroxylamine with > 99 % selectivity was obtained after only 2 h when the reaction was conducted at 25 °C in ethanol under an inert atmosphere using 0.1 mol% catalyst. Under these conditions, the composition-time profile showed that the reduction occurred via the direct pathway whereas reactions in air gave a mixture of azoxy-based products due to competing condensation resulting from reversible formation of N -phenylhydroxylamine. The initial TOF of 6,100 h−1 obtained after 10 min at 40 °C with 0.1 mol% 2 is among the highest to be reported for the metal nanoparticle catalysed reduction of nitrobenzene to N -phenylhydroxylamine and a significant improvement on 5 wt% Ru/C which gave a modest conversion of 21 % (initial TOF = 240 h−1) to a mixture of N -phenylhydroxylamine and aniline. A broad range of substituted N -aryl and N -heteroaryl nitroarenes were reduced to the corresponding N -arylhydroxylamine in high yield and with excellent selectivity by adjusting the reaction times. However, reduction of electron rich amino-substituted nitroarenes was extremely slow and resulted in reduction to the aniline with no evidence for the corresponding hydroxylamine. Complete reduction of amino substituted nitroarene is proposed to be facilitated by amine-assisted elimination of hydroxide from the hydroxylamine to afford a readily reducible quinondiimine-derived iminium intermediate that reacts with a surface hydride to liberate the amine. Under optimum conditions the catalyst could be reused five times for the reduction of nitrobenzene to N -phenylhydroxylamine with no detectable change in activity and only slight decrease in selectivity. [ABSTRACT FROM AUTHOR]

• Ultrafine RuNPs are stabilised by amino-modified polymer immobilized ionic liquid. • High activity for hydrolytic evolution of hydrogen from NaBH 4. • Kinetic studies confirm the hydrolysis is first order in catalyst and hydride. • Kinetic isotope studies with H 2 O/D 2 O and NaBH 4 /NaBD 4 support the proposed mechanism. • High activity retained over five reuses with only a minor reduction in conversion. Ruthenium nanoparticles stabilised by polymer immobilized ionic liquids catalyse the hydrolytic release of hydrogen from sodium borohydride. The composition of the polymer influences performance and ruthenium nanoparticles stabilised by an amine-decorated imidazolium-based polymer immobilised ionic liquid (RuNP@NH 2 -PIILS) was the most efficient with a maximum initial turnover frequency (TOF) of 177 mole H2.mol Ru −1.min−1, obtained at 30°C with a catalyst loading of 0.08 mol%; markedly higher than that of 69 mol H2.mol Ru −1.min−1 obtained with 5 wt% Ru/C and one of the highest to be reported for a RuNP catalyst. The apparent activation energy (Ea) of 38.9 kJ mol−1 for the hydrolysis of NaBH 4 catalysed by RuNP@NH 2 -PIILS is lower than that for the other polymer immobilized ionic liquid stabilised RuNPs, which is consistent with its efficacy. Comparison of the initial rates of hydrolysis in H 2 O and D 2 O catalysed by RuNP@NH 2 -PIILS gave a primary kinetic isotope effect (k H / k D) of 2.3 which supports a mechanism involving rate limiting oxidative addition of one of the O-H bonds in a strongly hydrogen-bonded surface-coordinated [BH 3 H−]—-H 2 O ensemble. The involvement of a surface-coordinated borohydride is further supported by an inverse kinetic isotope effect of 0.65 obtained from a comparison of the initial rates for the hydrolysis of NaBH 4 and NaBD 4 under the conditions of catalysis i.e., at a high hydride/catalyst mole ratio. Interestingly though, when the comparison of the initial rates of hydrolysis of NaBH 4 and NaBD 4 was conducted in dilute solution with a hydride/catalyst mole ratio of 1 a kinetic isotope effect (k H / k D) of 2.72 was obtained; this would be more consistent with concerted activation of both an O-H and B-H bond in the rate limiting step, possibly via a concerted oxidative addition-hydride transfer in the surface-coordinated hydrogen-bonded ensemble. Catalyst stability and reuse studies showed that RuNP@NH 2 -PIILS retained 71% of its activity over five runs; the gradual drop in the initial TOF with run number appears to be due to passivation of the catalyst by the sodium borate by-product as well as an increase in viscosity of the reaction mixture rather than leaching of the catalyst. [Display omitted] [ABSTRACT FROM AUTHOR]