X-Type Aluminyl Ligands for Transition-Metal Catalysis

Abstract

Transition-metal complexes that bear group-13 X-type metalloligands have attracted considerable interest on account of their strong σ-donicity, which can dramatically tune the reactivity of transition-metal catalysts. Among the group-13 X-type metalloligands, X-type aluminyl ligands are especially interesting due to the low electronegativity and strong Lewis acidity of the Al atom. However, transition-metal complexes that bear X-type aluminyl ligands had until recently remained elusive. In this perspective, we describe the reactivity of transition-metal complexes that carry a well-designed X-type PAlP pincer-ligand and their characteristic features, i.e., strong σ-donicity, trans-influence, reverse bond polarization, and Lewis acidity. These properties enable various catalytic transformations, including transfer dehydrogenation, highly efficient CO2 reduction, site-selective C–H-bond functionalization, and cooperative C–F- and C–O-bond functionalization, which are challenging to achieve using conventional catalyst systems.