Diverse Reactivity of ECp* (E = Al, Ga) toward Low-Coordinate Transition Metal Amides [TM(N(SiMe3)2)2] (TM = Fe, Co, Zn): Insertion, Cp* Transfer, and Orthometalation

The reactivity of the carbenoid group 13 metal ligands ECp* (E = Al, Ga) toward low valent transition metal complexes [TM(btsa)(2)] (TM = Fe, Co, Zn; btsa = bis(trimethylsilyl)amide) was investigated, revealing entirely different a reaction patterns for E = Al and Ga. Treatment of [Co(btsa)2] with Al Cp* yields [Cp* Co (mu-H) (Al (k(2)-(CH2SiMe2)NSiMe3) (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)(2)], complete ligand exchange gives FeCp*(2), irrespective of the employed stoichiometric ratio of the reactants. In contrast, treatment of [TM(btsa)(2)] (TM = Fe, Co) with GaCp* forms the 1:1 and 1:2 adducts [(GaCp*)Co(btsa)(2)] (2) and [(GaCp*)(2)Fe(btsa)(2)] (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)(2)], no Cp* transfer is observed on reaction with AlCp*; instead, the insertion product [Zn(Al(eta(2)-Cp*)(btsa))2] (4) is formed. In the reaction of [Co(btsa)2] with the trivalent [Cp*AlH2], transfer of the amide ligands without further ligand rearrangement is observed, leading to [Co(mu-H)4(Al(;eta Cp2-*)(btsa))(2)] (5).