From mixed group 13 cations [M(AlCp*) 3 ] + (M = Ga/In/Tl) to an Al 4 + cluster.

AlCp*-complexes with transition metals have shown to be highly reactive and enable C-H or Si-H bond activation. Yet, complexes of AlCp* with low-valent main-group metals are scarce. Here, we report the syntheses of [M(AlCp*) 3 ][Al(OR F ) 4 ] (R F = C(CF 3 ) 3 ) with M = Ga, In, Tl, which include the first covalent Al-In and Al-Tl bonds. For M = Ga, AlCp*-coordination induced the formation of the dication [Ga 2 (AlCp*) 6 ] 2+ in the solid state, which exhibits a solvent and temperature dependent monomer-dimer equilibrium in solution. By contrast, the In and Tl complexes are monomeric and prone to reduction to the metal by the electron-rich AlCp*-moieties. The QTAIM analysis suggests that the metal centres are already highly reduced in the complexes, while the positive charge is distributed onto the AlCp* units. Addition of Me 3 TACN (1,4,7-trimethyl-1,4,7-triazacyclononane) to the Ga- and Tl-complex salts resulted in an isomerization to the novel low-valent Al 4 + cation [(Me 3 TACN)Al(AlCp*) 3 ][Al(OR F ) 4 ]. Intermittently formed tetrahedral GaAl 3 + clusters could be structurally characterized. From a detailed mechanistic study of this isomerization, the very high yield and clean preparation of [(Me 3 TACN)Al(AlCp*) 3 ][Al(OR F ) 4 ] was devised from [M(Me 3 TACN)][Al(OR F ) 4 ] (M = Ga, Tl) and [(AlCp*) 4 ].