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Diverse Reactivity of ECp* (E = Al, Ga) toward Low-Coordinate Transition Metal Amides [TM(N(SiMe<sub>3</sub>)<sub>2</sub>)<sub>2</sub>] (TM = Fe, Co, Zn): Insertion, Cp* Transfer, and Orthometalation
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Citations
47
References
2017
Year
The reactivity of the carbenoid group 13 metal ligands ECp* (E = Al, Ga) toward low valent transition metal complexes [TM(btsa)<sub>2</sub>] (TM = Fe, Co, Zn; btsa = bis(trimethylsilyl)amide) was investigated, revealing entirely different reaction patterns for E = Al and Ga. Treatment of [Co(btsa)<sub>2</sub>] with AlCp* yields [Cp*Co(μ-H)(Al(κ<sup>2</sup>-(CH<sub>2</sub>SiMe<sub>2</sub>)NSiMe<sub>3</sub>)(btsa))] (1) featuring an unusual heterometallic bicyclic structure that results from the insertion of AlCp* into the TM-N bond with concomitant ligand rearrangement including C-H activation at one amide ligand. For [Fe(btsa)<sub>2</sub>], complete ligand exchange gives FeCp*<sub>2</sub>, irrespective of the employed stoichiometric ratio of the reactants. In contrast, treatment of [TM(btsa)<sub>2</sub>] (TM = Fe, Co) with GaCp* forms the 1:1 and 1:2 adducts [(GaCp*)Co(btsa)<sub>2</sub>] (2) and [(GaCp*)<sub>2</sub>Fe(btsa)<sub>2</sub>] (3), respectively. The tendency of AlCp* to undergo Cp* transfer to the TM center appears to be dependent on the nature of the TM center: For [Zn(btsa)<sub>2</sub>], no Cp* transfer is observed on reaction with AlCp*; instead, the insertion product [Zn(Al(η<sup>2</sup>-Cp*)(btsa))<sub>2</sub>] (4) is formed. In the reaction of [Co(btsa)<sub>2</sub>] with the trivalent [Cp*AlH<sub>2</sub>], transfer of the amide ligands without further ligand rearrangement is observed, leading to [Co(μ-H)<sub>4</sub>(Al(η<sup>2</sup>-Cp*)(btsa))<sub>2</sub>] (5).
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