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

Abstract

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(CF 3) 2CH 2(OCH 2CH 2) 2OMe and (biak)H=HOC(CF 3) 2CH 2OCH 2CH 2N(CH 2CH 2OMe) 2, with metal source reagents Sr(OPr i) 2 and BaH 2, 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 H 2O 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 SrF 2 and BaF 2 powders.