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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]

Platinum nanoparticles stabilized by imidazolium‐based phosphine‐decorated Polymer Immobilized Ionic Liquids (PPh2‐PIIL) catalyze the hydrolytic evolution of hydrogen from sodium borohydride with remarkable efficiency, under mild conditions. The composition of the polymer influences efficiency with the catalyst based on a polyethylene glycol modified imidazolium monomer (PtNP@PPh2‐PEGPIILS) more active than its N‐alkylated counterpart (PtNP@PPh2‐N‐decylPIILS). The maximum initial TOF of 169 moleH2.molcat−1.min−1 obtained at 30 °C with a catalyst loading of 0.08 mol% is among the highest to be reported for the aqueous phase hydrolysis of sodium borohydride catalyzed by a PtNP‐based system. Kinetic studies revealed that the apparent activation energy (Ea) of 23.9 kJ mol−1 for the hydrolysis of NaBH4 catalyzed by PtNP@PPh2‐PEGPIILS is significantly lower than that of 35.6 kJ mol−1 for PtNP@PPh2‐N‐decylPIILS. Primary kinetic isotope effects kH/kD of 1.8 and 2.1 obtained with PtNP@PPh2‐PEGPIILS and PtNP@PPh2‐N‐decylPIILS, respectively, for the hydrolysis with D2O support a mechanism involving rate determining oxidative addition or σ‐bond metathesis of the O−H bond. Catalyst stability and reuse studies showed that PtNP@PPh2‐PEGPIILS retained 70 % of its activity across five runs; the gradual drop in conversion appears to be due to poisoning of the catalyst by the accumulated metaborate product as well as the increased viscosity of the reaction mixture. [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]