Visible‐Light‐Driven Alcohol Dehydrogenation with a Rhodium Catalyst

Abstract

We report the photocatalytic dehydrogenation of alcohols with a Rh catalyst and I− in an acidic medium. The catalyst screening of a structurally diverse family of Rh complexes found [RhIII(dtbbpy)2(OSO2CF3)2](CF3SO3) (Rh7; dtbbpy=4,4′‐di‐tert‐butyl‐2,2′‐bipyridine) to be the best catalyst. All components (Rh7, HI, alcohol, and light) were found to be essential for the dehydrogenation to occur. Under optimal conditions, generation of both H2 and acetone (for isopropyl alcohol) was observed, which increased linearly for 4 days with no significant decrease in activity. The proposed mechanism involves the formation of [RhIII(dtbbpy)2(I)2]+ [Rh7(a)] followed by the generation of photoinduced I3− via a ligand (I−) to metal (RhIII) charge transfer. The resulting RhI species reduces H+ and I3− oxidizes the alcohol, which completes the catalytic cycle. Supporting evidence for the catalytic mechanism was obtained by using UV/Vis spectroscopy, electrospray ionization mass spectrometry, cyclic voltammetry and time‐dependent DFT calculations.

Silver-modified titania with enhanced photocatalytic and antimicrobial properties under UV and visible light irradiation

“…It must be pointed that the presence of a noble metal as co-catalyst is necessary for alcohol dehydrogenation [22,23]. Recently, the possibility of alcohol dehydrogenation by complexes of noble metals has been reported [24,25].…”

Light‐Driven Alcohol Splitting by Heterogeneous Photocatalysis: Recent Advances, Mechanism and Prospects

“…The only by‐product, hydrogen, is a sustainable energy carrier due to its high energy capacity [8–9] . It is worth noting that high selectivity of aldehydes or ketones can be achieved in this approach owing to the absence of oxidants [10–32] …”

“…Alcohol splitting is an uphill reaction (endothermic), implying that energy is required to drive this reaction [10–32] . Conventional alcohol splitting reactions are usually conducted at equal or above 90 °C [10–24] .…”

“…Photocatalysis has been applied in a variety of chemical transformations with high selectivity under mild conditions [33–37] . Light‐driven alcohol splitting (LDAS) catalyzed by heterogeneous or homogeneous catalysts under mild conditions (irradiation of visible light, room temperature) and in a readily available vessel (e. g. flask) has been demonstrated [26–32] . In particular, LDAS catalyzed by heterogeneous photocatalysts can be conducted under neat condition; more importantly, the photocatalysts can be easily separated from the reaction mixtures and reused, greatly benefitting synthetic chemistry [29–32] …”

Copper(i) pyrimidine-2-thiolate cluster-based polymers as bifunctional visible-light-photocatalysts for chemoselective transfer hydrogenation of α,β-unsaturated carbonyls

“…[35][36][37] Very recently, we have found that Cu(I) pyrimidine-2-thiolate clusters can efficiently catalyze transfer hydrogenation reactions via a cooperative metal hydride and ligand proton transfer mechanism. 38 Cu(I) N-heterocycle thiolate clusters are potentially attractive precursors for the construction of bifunctional photocatalyst MOFs based on the following considerations: (i) metal thiolate complexes can be used as co-catalysts for the production of hydrogen compatible with a photosensitizer, [39][40][41][42][43][44][45] (ii) Cu(I) Nheterocycle thiolates absorb visible light and are intensely luminescent with long uorescent lifetimes, [46][47][48] (iii) they can smoothly achieve such conversion at 100 C, 38 Single-crystal analysis revealed that 2 crystallized in the tetragonal space group P4 1 2 1 2, 3 crystallizes in the monoclinic space group C2/c. In 2, each "Cu 6 (dmpymt) 6 " unit is interconnected with the other four through "Cu 2 (m-I) 2 " linkages forming a 2D layer, which is further connected to equivalent layers via N-Cu-N bonds to form a 3D net (Fig.…”