A facile preparation method for homogeneous Ir catalysts for dehydrogenation and hydrogenation reactions involving N-heteroarenes

Abstract

The liquid organic hydrogen carrier (LOHC) technology is a promising route for efficient hydrogen storage, and Ir complexes belong to an important family of homogeneous catalysts applied in this field. We developed and optimized a “2-step” method for the synthesis of complex Cp*Ir(C₆H₃NF₃O)Cl. This complex, designated as T1 in this work, was originally referred to as 2c in ref. [Yamaguchi et al. J. Am. Chem. Soc., 2009, 131, 8410–8412]. The “2-step” method improved the yield of complex T1 and offered a simplified operational process, compared to the previously reported “sodium salt” method. The excellent catalytic activity of T1, synthesized by the “2-step” method was further confirmed. This method was further applied to synthesize other Ir catalysts, T2 and T3. 5-Fluoro-2-hydroxypyridine and 5-nitro-2-hydroxypyridine were assigned to prepare the dehydrogenation catalysts T2 and T3, respectively. Both T2 and T3 effectively catalyzed the dehydrogenation of 2-Me-THQ. Their catalytic activities followed the trend T1 > T2 > T3, highlighting the crucial role of electron-withdrawing ligands in enhancing catalytic performance. In addition, the precursor [Cp*IrHCl]₂ (H1) obtained through this “2-step” method, exhibited good performance in 2-Me-Q hydrogenation. H1 and T1 were also successfully applied to the hydrogenation and dehydrogenation of other nitrogen-containing carriers, respectively.