Isostructural Mg and Zn compounds: analogies and differences in reactivity

In recent years, active efforts to assess similarities and differences in the reactivity of isostructural magnesium and zinc complexes have witnessed reasonable growth. The advancements in their chemistry concerning catalytic reduction of compounds like olefins, imines, nitriles, carbonyls and CO₂, alkene isomerisation as well as hydrogen uptake and release have garnered attention. The unique characteristics of Mg and Zn stem from their similarities at the molecular level but differences in electrophilicity after complexation. This is reflected in the structures and/or chemistry of these isostructural complexes, making their study even more interesting. Consequently, the chemistry of Mg and Zn complexes with suitable co-ligands has seen progression both in terms of synthetic methodology as well as isolation of unique frameworks, ranging from mono- or bimetallic hydride complexes to multimetallic hydride clusters, cationic complexes, amidoboranes as well as σ-complexes with transition metals. The organisation of this review is based on the categories of ligand systems that stabilise these precarious complexes, specifically β-diketiminate and its derivatives, N-heterocyclic carbene motifs, NNNN-macrocyclic motifs, anionic nitrogen donor motifs and allylic donor motifs. The synthesis and structural aspects of these main group complexes are discussed, along with their reactivity, applications, and mechanistic insights into some of the reactions.