Alkaline-earth metal fluoroalkoxide complexes with multi-coordinated polyether appendage: synthesis and characterization

Four alkaline-earth metal alkoxide complexes of formula [M(meak)2] (1, M=Sr; 2, M=Ba) and [M(biak)2]2 (3, M=Sr; 4, M=Ba) were synthesized by the reaction of polyether substituted flouroalcohols, (meak)H=HOC(CF3)2CH2(OCH2CH2)2OMe and (biak)H=HOC(CF3)2CH2OCH2CH2N(CH2CH2OMe)2, with metal source reagents Sr(OPri)2 and BaH2, respectively. These complexes were characterized by 1H and 19F NMR spectroscopies and single crystal X-ray diffraction studies. The coordination geometry of 1 is best described as distorted trigonal dodecahedron, while complex 2 shows a similar coordination geometry, but possesses a H2O solvate linked to the alkoxy oxygen atom of the chelating meak ligands through H-bonding. Complexes [Sr(biak)2]2 (3) and [Ba(biak)2]2 (4) exist as dimers in the solid state in which the metal centers are linked by two bridging alkoxy oxygen atoms and encapsulated by a total of nine heteroatoms composed of a distorted tricapped trigonal prismatic geometry. Variable temperature 19F NMR studies of all complexes show simultaneous existence of two isomers in solution. Pyrolysis of these four complexes in air affords the expected SrF2 and BaF2 powders.