SYNTHESIS AND CHARACTERIZATION OF NEW ALKOXOTITANATES OF YTTRIUM, BARIUM, AND COPPER - SINGLE-CRYSTAL X-RAY-DIFFRACTION STRUCTURES OF CL2Y(TI-2(OPRI)(9)), (TI(OPRI)(5))BA(TI-2(OPRI)(9)), AND CLCU(TI-2(OPRI)(9))

The synthesis and characterization of new mixed-metal alkoxides of tit anium with yttrium, barium, and copper, achieved via salt elimination and acid-base reactions, is described. The metathesis reactions of KTi 2(OPri)(9) with anhydrous YCl3 (1:1 and 2:1) and CuCl2 (1:1) afford ch loro-functionalized heterobimetallic alkoxides Cl2Y{Ti-2(OPri)(9)} (1) , ClY{Ti-2(OPri)(9)}(2) (2), and ClCu{Ti-2(OPri)(9)} (3), respectively , in high yields. The barium-titanium derivatives [Ba{Ti-2(OPri)(10)}] (2) (4), {Ti-2(OPri)(9)}Ba{Ti(OPri)(5)} (5), and Ba{Ti-2(OPri)(9)}(2) (6) result from the reaction between [Ba(OPri)(2)](n), and Ti(OPri)(4) in 1:2, 1:3, and 1:4 molar ratios, respectively. All the new derivati ves (1-6) have been characterized by elemental analyses, variable-temp erature H-1 and C-13 NMR, infrared spectroscopy, cryoscopy, and single crystal X-ray diffraction studies for 1, 3, and 5. The crystallograph ic study of 1 reveals a mononuclear species where the yttrium atom, co ordinated by four alkoxide oxygen atoms of the {Ti-2(OPri)(9)}(-) unit and two chloride ligands, is in a pseudo-octahedral arrangement. The NMR (H-1 and C-13) and cryoscopic data for 1 indicate that the bioctah edral {Ti-2(OPri)(9)} framework, as observed in the solid state struct ure, is retained in solution also. The X-ray structure of copper deriv ative 3 exhibits a triangular heterometallic core CuTi2(mu(2)-OPri)(3) (mu(3)-OPri)(2) with chloride as a terminal ligand on copper. Each tit anium bears two terminal OPri groups and displays a distorted octahedr al geometry whereas copper has a pseudotrigonal bipyramidal environmen t. The high-temperature NMR studies for the paramagnetic 3 are in agre ement with Curie law behavior; the isotropic shifts indicate that the OPri groups bound directly to the Cu-II center experience a greater pa ramagnetic influence in comparison to OPri groups attached to titanium only. Barium titanates reveal an interesting observation of structura l and stoichiometry (Ba/Ti) change. The dimeric compound 4 (Ba/Ti, 1:2 ) reacts with 1 mol of Ti(OPri)(4) to offer mononuclear 5 with a Ba/Ti stoichiometry of 1:3; on further addition of 1 mol of Ti(OPri)(4), 5 is converted to 6 (Ba/Ti, 1:4). X-ray crystallography performed on 5 s hows the molecular structure to be formed by the coordination of monoa nionic {Ti(OPri)(5)}(-) and {Ti-2(OPri)(9)}(-) units to Ba2+ in bi- an d tetradentate fashion, respectively. The coordination figure of the c entral atom, barium, corresponds to a trigonal prism distorted toward an octahedron. Crystal data for 1: monoclinic space group Cc, a = 21.6 18(14) Angstrom, b = 9.878(5) Angstrom, c = 19.949(13) Angstrom, beta = 109.51(4)degrees, V = 4015(4) Angstrom(3), Z = 4. Crystal data for 3 : triclinic space group <P(1)over bar>, a = 10.085(2) Angstrom, b = 10 .210(2) Angstrom, c = 21.551(4) Angstrom, alpha = 84.40(3)degrees, bet a = 84.03(3)degrees, gamma = 60.86(3)degrees, V = 1924.9(6) Angstrom(3 ), Z = 2. Crystal data for 5: triclinic space group <P(1)over bar>, a = 11.850(2) Angstrom, b = 13. 888(3) Angstrom, c = 18.716(4) Angstrom, alpha = 86.08(3)degrees, beta = 89.15(3)degrees, gamma = 83.36(3)degr ees, V = 3052.3(11) Angstrom(3), Z = 4.