Organozinc ligands in transition metal chemistry

Synthetic strategies and mechanistic pathways for the formation of transition metal–organozinc compounds and their structural properties are reviewed. Herein, two groups of zinc sources are taken into account. Firstly, Zn(II) compounds ZnR2 (R = organic group) which includes the discussion of structural features and quantum chemical results of the recently reported zinc-rich and highly coordinated [M(ZnR)n] molecules (n ≥ 8; M = Mo, Ru, Rh, Ni, Pd, Pt; R = Me, Et, Cp*). Secondly, the recently discovered stable Zn(I) derivative [Zn2Cp*2] (Cp* = pentamethylcyclopentadienyl) leads to coordination compounds with TM–Zn bonds (TM = transition metal) on reaction with suitable transition metal complexes. The different concepts in the formation of TM–Zn bonds are oxidative addition of Zn–C and Zn–Zn bonds, the use of bis(transition metal)zinc compounds, hydride abstraction, the use of substitution labile transition metal compounds, salt elimination reactions, radical mechanisms, alkane elimination, dissociation/association mechanisms and finally ZnR/GaR exchange reactions.

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► ZnCp2 as a source for the formation of transition metal–organozinc compounds.
► Synthesis of zinc-rich compounds.
► Organozinc-alkyl ligands ZnR (R = Me, Et) as modulating agents for the reactivity of transition metal centres.
► Zinc-rich compounds as molecular model systems for intermetallic phases of the Hume–Rothery type.
► [Zn2Cp*2] as a natural source for the formation of {ZnZnCp*} and ZnCp* ligands as well as a Cp* transfer reagent.