The transition from traditional carbon-based energy systems into more sustainable and renewable ones is a crucial subject matter nowadays. In this regard, molecular hydrogen arises as one of the main and most efficient energy vectors as its reaction with oxygen provides energy and only generates water as a by-product. The difficulties in its storage and transport can be overcome with Liquid Organic Hydrogen Carriers (LOHC), organic substances that store hydrogen through catalytic hydrogenation and dehydrogenation processes over multiple cycles and may support a future hydrogen economy. In this sense formic acid is considered as one of the most promising LOHC. Dehydrogenation reactions play also a key role in the valorization of readily available and inexpensive bulk chemicals such as glycerol, or in the production of fine chemicals like carbonyl and carboxylic compounds from primary and secondary alcohols. Interestingly, under acceptorless conditions dehydrogenation reactions generate valuable molecular hydrogen as by-product, making the processes more competitive from an economic point of view. Within this context, Ir-NHC compounds have been stablished as leading catalysts in the dehydrogenation processes of a wide range of substrates. In the present work, we depict the synthesis of different Ir(I) and Ir(III) complexes bearing asymmetric NHC ligands with a pyridyl fragment and a rigid oxygen-donor moiety in its structure. These compounds have shown to be efficient catalysts for the dehydrogenation of several substrates such as glycerol, benzyl alcohol derivatives and formic acid [Scheme 1: acceptorless dehydrogenation reactions catalyzed by Ir-NHC complexes]. The coordination mode of the ligands plays an essential role in the dehydrogenation processes, resulting in marked differences in catalytic activity.

Resumen del póster presentado a la XXXVIII Reunión Bienal de la Real Sociedad Española de Química, celebrada en el Palacio de Congresos de Granada, del 27 de junio al 30 de junio de 2022.

Peer reviewed