The combination of equimolar amounts of LiOAr and Mg(OAr)(2) (OAr = aryloxide) in polar media afforded several lithium aryloxomagnesiates. Factors influencing the structural chemistry of the compounds, such as the degree of ligand bulk, type of Lewis base donors, and crystallization solvent, are examined. Structural characterization reveals a discrete, solvent-separated species, [Li(thf)(4)][Mg(BHT)(3)]center dot THF (1) (BHT = 2,6-t4BU(2)4-MeC6H2O) and a family of molecular compounds with various Li/Mg stoichimetries, including a 1:1 Li/Mg ratio in [LiMg(Odpp)(3)(thf)(2)]center dot 0.5PhMe (2) (Odpp =2,6-Ph2C6H30) and [Li(Et2O)Mg(OdpP)(3)]center dot 0.5PhMe (3), a 2:1 Li/Mg ratio as in [{Li(thf)(2)}(2)Mg(OMes)(4)]center dot 2THF (4) (OMes = 2,4,6-Me3C6H2O) and [{Li(tmeda)}(2)Mg(m-OdtP)(4)]center dot 0.5Et(2)O (5) (m-Odtp = 3,5-tBU(2)C(6)H(3)O), and a novel 2:3 Li/Mg ratio in [{Li(thf)(2)}(2)Mg-3(m-OdtP)(8)(thf)(2)]center dot 3THF (6). Two new homometallic magnesium bis(aryloxides), Mg(OdPP)(2)(thf)(2) (7) and Mg(OdPP)(2)(Et2O)(2) (8), are also included for the sake of comparison. The solution behavior of the heterobimetallic compounds in arene and polar solvent is analyzed by H-1 NMR spectroscopy.