REACTIONS OF ZROCL2-CENTER-DOT-8H(2)O WITH CARBOXYLIC-ACIDS AND THIONYL CHLORIDE - CRYSTAL AND MOLECULAR-STRUCTURES OF K-4[ZR(MAL)(4)]CENTER-DOT-2H(2)O AND K-4[ZR(DIPIC)(3)](2)CENTER-DOT-13.5H(2)O

Reactions of ZrOCl2. 8H(2)O in aqueous solution with a carboxylic acid in the presence of K2CO3 have been studied as a route to Zr-IV-carbox ylates. With malonic acid (HO2CCH2CO2H) (H(2)mal) the product has been identified as K-4[Zr(mal)(4)]. 2H(2)O (1) by X-ray crystallography. T he individual eight-coordinate zirconium anions contain four bidentate (OO') malonate anions with the metal geometry approximating to a squa re antiprism with each chelating ligand spanning the two square faces, Zr-O 2.091(3)-2.288(3) Angstrom. The four potassium cations feature i rregular coordination spheres of oxygen atoms [from both H2O and (mal) ligand molecules] with a 7-9 coordination range. With 2,6-dicarboxypi colinic acid (HO2CC5NH3CO2H) (H(2)dipic) the product has been characte rised as K-4[Zr(dipic)(3)](2). 13.5H(2)O (2) following X-ray diffracti on studies. The structure consists of two [Zr(dipic)(3)](2-) anions, f our potassium cations and lattice solvate (H2O) molecules. Individual anions feature nine-coordinate zirconium in which each dipic ligand is terdentate, being bonded via one N (pyridine) and two O (carboxylate) atoms. The metal geometry approximates to tricapped trigonal prismati c with each nitrogen atom capping a regular face of four oxygen atoms, Zr-O, 2.216(6)-2.261(6) Angstrom; Zr-N, 2.343(8)-2.361(7) Angstrom. T he potassium cations show similar environments to those observed in st ructure (1). Dehydration of ZrOCl2. 8H(2)O using SOCl2 in the presence of an excess of THF effects removal of coordinated H2O molecules and hydroxy bridging groups to provide the anhydrous bis-adduct ZrCl4(thf) (2) in good yield (72%).