Elemental Magnesium as an Early Transition Metal Substitute: From Pentafulvene Coordination to Deprotonation of Amines

Abstract The reaction of magnesium turnings and 6,6‐di‐ para ‐tolylpentafulvene was investigated. Under mild conditions, the magnesium dissolves, forming the Mg II complex 1 with a π‐η 5 : σ‐κ 1 coordinating ligand of the dimerized pentafulvene, analyzed by NMR and XRD investigations. As a magnesium pentafulvene complex was a possible intermediate, amines were employed as intercepting agents. Thereby, the amines were formally deprotonated by elemental magnesium, yielding the first examples of Cp'Mg(THF) 2 NR 2 complexes. This reaction competes with the formation of 1 and a consecutive formal [1,5]‐H‐shift forming an ansa‐magnesocene. Employing amines with low basicity gave quantitative conversion to the amide complexes.