A Modular Approach to Asymmetric Mg(I) Complexes Using a Unique Cyclopentadienyl Mg(I) Complex

The first Mg I complexes with non‐N ligands have been isolated and were fully characterized. Reaction of [(BDI*)MgNa] 2 ( III ) with MgCp* 2 gave quantitative conversion to (BDI*)MgMgCp* ( 1 ); BDI* = HC[ t BuC = N(DIPeP)] 2 , DIPeP = 2,6‐Et 2 CH‐phenyl) and Cp* = pentamethylcyclopentadienyl. A similar reaction with CaCp* 2 did not give (BDI*)MgCaCp* but led to insertion of the formal Mg° centre in the benzylic C─H bond, an oxidative addition that resulted in a mixed Mg/Ca hydride complex. The Cp* ligand in the unique (BDI*)MgMgCp* complex can be exchanged by addition of LM (M = Li, Na, K) complexes, resulting in formation of (BDI*)MgMgL and insoluble (Cp*M) n . This modular approach worked for Cp*/N(SiMe 3 ) 2 exchange but not for the substitution of Cp* by P(SiMe 3 ) 2 or other PR 2 ligands. Reaction of (BDI*)MgMgCp* with a bulky NaOAr reagent led to quantitative formation of (BDI*)MgMgOAr·THF, a first Mg I complex stabilized with an aryloxide ligand. All products have been fully characterized by X‐ray diffraction and NMR methods. A computational study gives insight in the thermodynamics of formation and electronic structures.