The solid-state reaction of MgBr2 and NaB3H 8 at 20°C, followed by sublimation at 80°C and 0.05 Torr, affords Mg(B3H8)2 as a white solid. Similar reactions with MgBr2(Et2O) and MgBr2(Me 2O)1.5 afford the crystalline ether adducts Mg(B 3H8)2(Et2O)2 and Mg(B3H8)2(Me2O)2, respectively. In contrast, reactions of MgBr2 with NaB 3H8, the presence of excess solvent result in the formation of nonvolatile, probably ionic, magnesium compounds of the type [MgLx][B3H8]2. The adducts Mg(B 3H8)2(Et2O)2 and Mg(B3H8)2(Me2O)2 are the first crystallographically characterized magnesium complexes of the B 3H8- ligand; in both structures, the magnesium center adopts a distorted cis-octahedral geometry with two bidentate B 3H8 groups and two Et2O ligands. Owing to their volatility, Mg(B3H8)2(Et2O) 2 and Mg(B3H8)2(Me 2O)2 are potential precursors for the deposition of MgB2 thin films, although preliminary efforts to employ them as chemical vapor deposition sources produce boron-rich MgBx films instead, with x ≈ 7. Finally, the synthesis and structure of Cp 2Mg(thf) are described: this mono-thf adduct of Cp2Mg bears two η5-Cp groups, unlike other Lewis base adducts of Cp2Mg, which contain one η5-Cp group and one η1- or η2-Cp group.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry