Silica-supported subnanometric PtZn particles, prepared via surface organometallic chemistry, are highly productive and selective for propane dehydrogenation.

Small and narrowly distributed Cu nanoparticles, supported on SiO 2 decorated with isolated Ti IV sites, prepared through surface organometallic chemistry,s howeds ignificantly improved CO 2 hydrogenationa ctivity and CH 3 OH selectivity compared to the corresponding Cu nanoparticles supportedo nS iO 2 .T hese isolated Lewis acid Ti IV sites, evidenced by UV/Vis spectroscopy, are proposed to stabilize surface intermediates at the interface between Cu nanoparticlesa nd the support.The selective hydrogenation of CO 2 to CH 3 OH, together with the production of H 2 from renewable energy sources (e.g.,i ntermittent excesse nergy generatedf rom wind or solarp ower) is essential to av irtuous sustainable closed-carbon fuel cycle. [1][2][3][4] Its practice, however,i sc omplicated by the parasitic reversew ater-gas-shift (RWGS) reaction, which forms CO instead. The most prominent catalysts for selective CO 2 hydrogenation to CH 3 OH are Cu-based, although their activity and CH 3 OH selectivityd ramatically depend on the oxide support. [5][6][7][8] Cu supportedo nZ rO 2 (Cu/ZrO 2 ,i nw hich "Cu/X"d enotes Cu nanoparticles dispersed on support X) has shown promising activity and high CH 3 OH selectivity compared to Cu/ SiO 2 . [9][10][11][12] Whereas SiO 2 can be considered as an inert support for the Cu nanoparticles that catalyzet he reaction, ZrO 2 provides Zr IV sites interfacing Cu nanoparticles that act as Lewis acid sites andp romote CH 3 OH synthesis. [9] In fact, Cu nanoparticles supported on SiO 2 decorated with isolated Zr IV sites show CO 2 hydrogenationa ctivity andC H 3 OH selectivity nearly identicalt ot hose for Cu/ZrO 2 , [13] underscoring the importance of these Lewis acid sites at the periphery of Cu nanoparticles for the selective hydrogenation of CO 2 to CH 3 OH.In contrast, Cu/TiO 2 has been observed to be av ery poor CO 2 hydrogenation catalystw ith low reaction rates and low CH 3 OH selectivity, [7,8,14] in spiteo ft he ability of Ti IV metal cen- [a] Dr.

The selective hydrogenation of CO 2 to CH 3 OH is a crucial part of efforts to mitigate climate change via the methanol economy. Understanding the nature and role of active sites is essential for designing highly active and selective catalysts. Here, we examine Cu nanoparticles dispersed on TiO 2 and Ti-containing SiO 2 supports, where the Ti moieties of these materials are reducible to different extents, using a surface organometallic chemistry approach, together with state-of-the-art characterization methods (UV− vis, infrared (IR), electron paramagnetic resonance (EPR), and nuclear magnetic resonance (NMR) spectroscopies and in situ transmission electron microscopy (TEM)). Cu nanoparticles are small and well-dispersed on isolated, dimeric, and oligomeric Ti moieities on SiO 2 when reduced or when the material has been oxidized via exposure to air, but they are small only in the latter case for Cu dispersed on the bulk oxide TiO 2 . Large Cu nanoparticles, present on TiO 2 when reduced, redisperse upon exposure to air, likely associated with the facile oxidation of the reduced TiO 2 surface, and agglomerate again when reduced in situ within the electron microscope. CH 3 OH formation rates and selectivities on Cu/TiO 2 are low as a result of these large Cu nanoparticles and the ability of TiO 2 to catalyze the hydrogenation of CO 2 to CO. After accounting for the CO formation rates of the support itself, the CH 3 OH selectivities are similar for all catalysts (and greater than that for Cu/SiO 2 , where SiO 2 is considered as an innocent support), suggesting that Ti sites in all materials have a similar nature and role. These Ti sites act as Lewis acid sites, whose presence is evidenced by pyridine adsorption studies using IR and NMR spectroscopies, that stabilize the same surface intermediates at the interface of Cu nanoparticles and the support, despite differences in the reducibility of these Ti species.

Morpholine ketene aminal is employed in iridiumcatalyzedasymmetric allylic alkylation reactions as asurrogate for amide enolates to prepare g,d-unsaturated b-substituted morpholine amides.Kinetic resolution or,alternatively,stereospecific substitution affords the corresponding products in high enantiomeric excess.T he utility of the products generated by this method has been showcased by their further elaboration into amines,k etones,o ra cyl silanes.Ap utative catalytic intermediate (h 3 -allyl)iridium(III) with achiral P, Olefin-ligand was synthetized and characterized for the first time.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.