ABSTRACT p‐Block complexes containing unsupported metal─metal bonds can activate small molecules via mechanisms that complement and contrast with those of d‐block metal complexes. Here we report the synthesis of a new family of heterobimetallic Al─Zn complexes (Ar Nacnac) Zn─Al (Cp*) (X) (Ar = Dep, X = Cl, Br, I; Ar = Dipp, X = Cl, Br; Ar Nacnac = HCC (Me) N (Ar) 2 ; Ar = Dep, C 6 H 3 Et 2 ‐2, 6; Dipp, C 6 H 3 i Pr‐2, 6; Cp* = C 5 Me 5), by insertion of in situ‐generated “AlCp*” into the Zn─X bonds of parent dimeric zinc Ar Nacnac halide complexes Zn (Ar Nacnac) (μ‐X) 2. We find that the reactions of the newly formed Al─Zn complexes with N, Nʹ ‐dicyclohexylcarbodiimide (DCC) proceed by migratory insertion into the Al─Zn bond to give Zn (Ar Nacnac) μ 2 ‐C (NCy) 2 ‐κ 1 ‐ C, κ 2 ‐ N, N ʹAl (Cp*) (X) (Ar = Dep, X = Cl, Br, I; Ar = Dipp, X = Cl, Br) as expected, but for the Dipp Nacnac derivatives a second equivalent of DCC inserts into the Al─Cp* moiety to afford Zn (Dipp Nacnac) μ 2 ‐C (NCy) 2 ‐κ 1 ‐ C, κ 2 ‐ N, N ʹAl (Cl) κ 2 ‐ (NCy) 2 C‐η 1 ‐Cp*‐κ 2 ‐ N, N ʹ or Zn (Dipp Nacnac) (Br) μ 2 ‐C (NCy) 2 ‐κ 1 ‐ C, κ 2 ‐ N, N ʹAlκ 2 ‐ (NCy) 2 C‐η 1 ‐Cp*‐κ 2 ‐ N, N ʹ, with concomitant halide migration giving a Zn─Br bond in the latter complex. These results show that non‐innocent reactivity of Al─Cp*, widely assumed to be a spectator ligand in heterobimetallic complexes, can be switched on by subtly tuning ligand steric bulk about Al─Zn bonds.
Hemsworth et al. (2026) studied this question.