Low Valent Magnesium Chemistry with a Super Bulky β-Diketiminate Ligand.

The steric bulk of the well-known BDI ligand (CH[C(CH )N-DIPP] , DIPP=2,6-diisopropylphenyl) was increased by replacing isopropyl for isopentyl groups. This very bulky BDI ligand could not stabilize the radical species ( BDI)Mg : reduction of ( BDI)MgI with Na gave ( BDI) Mg with a rather long Mg-Mg bond of 3.0513(8) Å. Addition of TMEDA prior to reduction gave complex ( BDI) Mg (C H ), which could also be obtained as its THF adduct. It is speculated that combination of a bulky spectator ligand and TMEDA prevents dimerization of the intermediate Mg radical, which then reacts with the benzene solvent. Complex ( BDI) Mg (C H ), which formally contains the anti-aromatic anion C H , reacted with tBuOH as a Brønsted base to 1,3- and 1,4-cyclohexadiene and with H as a two electron donor to ( BDI) Mg H and C H . It also reductively cleaved the C-F bond in fluorobenzene and gave ( BDI)MgPh, ( BDI)MgF, and C H .