Análise estrutural de polímeros bidimensionais de fosfinatos de metais alcalinos e alcalinos terrosos

Abstract

In this work, the structures of three alkali and alkali-earth metal complexes of phenylphosphinate ligands and ethylphosphinate ligands, (4) catena-poli- [Ba(O2PHPh)2(OH2)], (5) catena-poli-[Na(O2PHPh)] e (6) catena-poli- [Ca2(O2PHEt)4(OH2)], were determined and analysed. In a typical synthesis, the compounds were prepared by the reaction of barium and sodium acetates with phenylphosphinic acid or calcium acetate with ethylphosphinic acid, under an argon atmosphere. The mixture refluxed for 2-3 hours to give a clear, colourless solution. After removal of the solvent, a microcrystalline white powder, (1) [Ba(O2PHPh)2], (2) [Na(O2PHPh)] and (3) [Ca(O2PHPh)2]. The compound catena-poli-[Ba(O2PHPh)2(OH2)] (4) was obtained by crystallization in water/methanol. Its structure belongs to the orthorhombic system and space group Pnma. The cell parameters are a= 8.0397(3) Å, b= 32.2778(17) Å, c= 5.6487(3); the refinement gives R1 = 0.028 and wR2 = 0.0637. The Ba ion has a capped trigonal prism geometry coordination formed by seven oxygen atoms, six from phenyphosphinate ligand and one from the molecules of water. The phenylphosphinate ligand forms bridges with Ba2+ ions, creating a two-dimensional coordination polymer parallel to the ac plane. The Ba O distances range between 2.743(3) Å and 2.883(3) Å. The compound catena-poli-[Na(O2PHPh)] (5) was obtained by crystallization in water/methanol. Its structure belongs to the monoclinic system and space group P21/c with cell parameters a = 5.7065(3) Å, b = 30.6702(15) Å, c = 11.7123(5) Å, β = 91.929(3)°; the refinement gives R1 = 0.0487 and wR2 = 0.1112. The three crystallographically independent Na+ ions show pyramidal quadratic and trigonal prismatic coordination geometries. Five phenylphosphinate ligands coordinate to the Na2 and Na3 center. The Na1 ion bonds to six oxygen atoms from four phenylphosphinate ligands, with two chelating. The phenylphosphinate ligand forms bridges with Na+ ions, creating a two-dimensional coordination polymer parallel to the ix ac plane. The Na O distances range from 2.290(2) Å to 2.479(2) Å for the pyramidal quadratic Na+ ion and between 2.209(2) Å and 2.632(2) Å for trigonal prismatic Na+ ion. The compound catena-poli-[Ca2(O2PHEt)4(OH2)] (6) was obtained by crystallization in water/methanol. Its structure belongs to the monoclinic system and space group P21/c with cell parameters a= 12,2082(4) Å, b= 9,5333(3) Å, c= 18,3098(6) Å, β = 99,868(2)°; the refinement gives R1 = 0,0436 and wR2 = 0,0993. The two crystallographically independent Ca2+ ions show octahedral coordination geometries. The first bonds to six oxygen atoms each from a bridging ethylphosphinate ligand. The second bonds to six oxygen atoms, five each from a bridging ethylphosphinate ligand and one molecule of water. The ethylphosphinate ligand forms bridges with Ca2+ ions, creating a two-dimensional coordination polymer parallel to the bc plane. The Ca O distances range between 2.265(2) Å and 2.410(2) Å.