title: [(C5H5)Co(P(O)(OH)2)3H]: a novel organometallic tris-phosphonic acid that dissolves glass to form a six-coordinate silicon complex.
abstract: The sodium salt of the tripodal oxygen ligand Na[(C5H5)Co(P(O)(OMe)2)3] (1) reacts with gaseous hydrogen chloride in dichloromethane to give sodium chloride and [(C5H5)Co(P(O)(OMe)2)3H2]Cl (2). Addition of an equimolar amount of 1 leads to precipitation of sodium chloride again to yield the acid form of the ligand [(C5H5)Co(P(O)(OMe)2)3H] (3). Its solid-state structure contains a very short intramolecular OH.O hydrogen bond. The compound hydrolyses in boiling water to give methanol and the title complex [(C5H5)Co(P(O)(OH)2)3H] (4). This complex is a rather strong tris-phosphonic acid (pK(a1) 2.0, pK(a2) 4.0, pK(a3) 6.3, and pK(a4) 9.6). Attempts to grow single crystals of this highly water-soluble yellow crystalline compound lead to the silicon complex [((C5H5)Co[P(O)(OH)2]2[P(O)2(OH)])(2)Si].8 H2O (5). The crystal structure determination shows that it is a molecular complex of two tris-phosphonic acids that each act as a tris-chelating ligand. Additional water molecules form a complex net of hydrogen bonds between the complexes of 5. The SiO6 octahedron is only insignificantly distorted with Si-O bond lengths of 1.78 A. Complex 4 reacts with stoichiometric amounts of potassium carbonate to yield the potassium salt K[(C5H5)Co(P(O)(OH)2)3] (6). The crystal structure of 6 has also been determined. In the solid state it is a two-dimensional coordination polymer with each potassium ion being coordinated by twelve oxygen atoms of six tris-phosphonic acids.
authors.affiliation: Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität, Düsseldorf Universitätsstrasse 1, 40225 Düsseldorf, Germany. klaeui@uni-duesseldorf.de
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kläui
authors.forename: Nicole
authors.initials: N
authors.lastname: Mocigemba
authors.forename: Annette
authors.initials: A
authors.lastname: Weber-Schuster
authors.forename: Ralf
authors.initials: R
authors.lastname: Bell
authors.forename: Walter
authors.initials: W
authors.lastname: Frank
authors.forename: Dietrich
authors.initials: D
authors.lastname: Mootz
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Poll
authors.forename: Hartmut
authors.initials: H
authors.lastname: Wunderlich