Sustainable and selective transfer hydrogenation using waste shrimp shell‐based tetrazene‐Ru (II) para‐cymene catalyst with ethanol as a hydrogen source

Abstract

Sustainable chemical research emphasizes chitosan‐based catalysts and the need to explore the direct utilization of waste shrimp shells, whereas the use of ethanol as a hydrogen source in transfer hydrogenation is less explored due to its unfavorable redox potential, higher energy barriers, generation of reactive intermediates, and catalyst poising via metal carbonyl species or decarbonylation. Herein, we disclosed an efficient synthetic approach, conducted at ambient temperature, for surface functionalization of waste shrimp shells with 3‐(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)‐1,2,4,5‐tetrazine (DMPZ‐Tz) via nucleophilic substitution using 3,6‐bis(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)‐1,2,4,5‐tetrazine (BDMPZ‐Tz). This method results in a color change and a 75% increase in surface nitrogen content, eliminating the need for multiple syntheses and harsh reaction conditions. We utilized the strong coordination property between DMPZ‐Tz and [Ru(p‐cym)Cl2]2/RuCl3.3H2O to develop ruthenium‐embedded transfer hydrogenation catalysts supported on shrimp shells. These catalysts were employed for the selective transfer hydrogenation of unsaturated carbonyl/aldehydes to saturated carbonyl/alcohols, utilizing ethanol as the hydrogen source and potassium carbonate as the base. The performance, selectivity, and reusability of the catalyst were thoroughly assessed through spectroscopic studies, in‐situ monitoring of the reaction progress, initial rate kinetics, and control experiments. The obtained results strongly indicated that the anchoring of DMPZ‐Tz played a crucial role in achieving superior performance compared with catalysts synthesized without it or utilizing its homogeneous counterparts. The catalyst exhibits efficient reactivity, selectivity, and broad substrate scope.

Chitosan as a Bio-Based Ligand for the Production of Hydrogenation Catalysts

“…Further, the high conversion obtained for all rounds of recycling confirms the stability of the Ru(0)-CS catalytic species. In agreement with the literature, Ru(0)-CS nanoparticles were active in more extreme conditions than Rh(0)-CS nanoparticles but were more recyclable than the latter [44].…”

“…To study the activity of M(0)NPs-CS and optimize hydrogenation reaction conditions, preliminary experiments were carried out using (E)-cinnamaldehyde (I) as a model substrate and relevant data are reported in Table 1. As previously mentioned, the hydrogenation of (I) is challenging due to the possible formation of several by-products [44,[80][81][82][83][84][85] and is often chosen as model reaction considering both its scientific and industrial relevance [84][85][86][87].…”

“…Since no data are available on the hydrogenation of (I) with CS nanoparticles, in order to evaluate the efficiency of Rh(0) and Ru(0)-CS as tested in this work, was comparison with heterogeneous Rh(0) and Ru(0) catalysts reported in the literature was carried out [44,88]. According to a very recent work by Patil and co-workers, results achieved with Rh(0) and Ru(0)-CS are particularly interesting, since, in most cases, heterogeneous catalysts reported in the literature have modest activity and selectivity, requiring harsh conditions and environmentally unfriendly organic solvents [44,[86][87][88][89][90][91][92][93][94][95].…”

“…In fact, CS has been widely studied as a ligand for the preparation of homogeneous and heterogeneous catalysts employed for carbon-carbon coupling, oxidation, hydrogenation and click reactions, among others [25,[33][34][35][36][37][38][39]. Concerning hydrogenation reactions, various examples have been reported in the literature regarding the use of chitosan as a ligand in the presence of Pd(0) and Pd(0) nanoparticles supported on silica [33,36,[40][41][42], while Rh(0) and Ru(0) have been investigated less [43][44][45][46].…”

“…ligand in the presence of Pd(0) and Pd(0) nanoparticles supported on silica [33,36,[40][41][42], while Rh(0) and Ru(0) have been investigated less [43][44][45][46].…”