Synthesis and characterization of monomeric Ba and Sr complexes with malonate and Lewis base ligands

The reaction of barium or strontium metal in ammonia gas-saturated THF with two equivalents of dimethyl malonate (dmalH) in the presence of tetraethylene glycol dimethyl ether (tetraglyme) or 1,1,4,7,7-pentamethyldiethylenetriamine (pmdt) yields Ba(dmal)2(tetraglyme) (1), Ba(dmal)2(pmdt) (2), Sr(dmal)2(tetraglyme) (3), and Sr(dmal)2(pmdt) (4) as colorless crystals in reasonable yields (45–52%). These complexes have been characterized by spectroscopic methods (IR and 1H- and 13C-NMR) and elemental analysis data. Molecular structures of 1, 3, and 4 have been determined by X-ray diffraction studies and have revealed that they are monomeric and the tetraglyme or pmdt ligand wraps around a central metal atom in a meridional plane with the dmal ligands on opposite sides of this plane.