The donor-free magnesocene analogues bis(1-methylboratabenzene)magnesium (1) and bis[3,5-dimethyl-1-(dimethylamino)boratabenzene] magnesium (2) are synthesized in good yields by the reactions of dimethyl-magnesium with (trimethyistannyl)dihydrobohnine precursors 3 and 4. Ln the crystalline stale, both 1 and 2 possess sandwich structures with eta (6)-coordinated;boratabenzene ligands and display crystallographic centrosymmetry. Compound 1 reacts with the nitrogen donor 2,2'-bipyridine to give the Lewis base adduct (1)(bipy) (equivalent to5). In the crystal structure of 5, one boratabenzene ligand is eta (6)-bonded to the central metal while the other ligand adopts an eta (1)-bonding mode. Crystallization of compound 2 from THF produces the solvate (2)(THF)(2) (equivalent to6), which exhibits a distorted tetrahedral N2O2 coordination environment-around the magnesium atom. The average Mg-N bond distance is 2.141(3) Angstrom, and the N-Mg-N angle is 148.0(1)degrees. The observation of an aminoboratabenzene that is solely a-bonded to a metal is without precedent.