ADVANCEDMATERIALS FOR OF'TICSAIWELECI'RONICS, VOL5.1-10 (1995) zyxw The X-ray Crystal and Molecular Structure of [Ba(TDFND),.tetraglyme] zy ,* the First Molten Barium Precursor for MOCVD Applications Jason A. zyxwvuts P. Nash,' John C. Barnes,b David J. Coie-Hamilton,'t Barbara C. Richards,' Stephen L. Cook' and Michael L. Hitchmand 'School of Chemistry, University of St Andrews, St Andrews, Fife KY16 9ST, U.K., bDepartmentof Chemistry, Universityof Dundee, Dundee, Tayside DD1 4HN, U.K., T h e Associated Octel Co. Ltd., Oil Sites Road, Ellesmere Port, Wirral, Merseyside L65 4HF, U.K, dDepartment of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 IXL, U.K. At 150 K [Ba(TDFND),.tetraglyme] crystallises in the Pl/.c space group with zyx a= 17.15(2) A, The barium atom is ninsco-ordinate, with binding to all the 0 atoms. The two BaTDFND rings are planar but tilted by 26" from being co-planar. The five 0 atoms of the tetraglyme ligand are also essentially co-planar, but this plane subtends angles of 88.8(1)' and 67.4(1)0 to the two BaTDFND planes. The BaO (TDFND) bond lengths are longer than for other related compounds, but the Ba-0 (tetraglyme) bond lengths are similar to those in [Ba(HFA),.tetragiyme] (HFA I CF,C(O)CHC(O)CF,). The low melting point and the fact that [Ba(TDFND),.tetraglyme], alone of barium complexes of this kind, can be evaporated without decomposition at 1 atm are attributed to lower intermolecular forces for this compound and to its greater thermal stability. KEYWORDS b= 10.735(5) A, C= 22.830(7) A, f5 = 97.56(7)", V= 4165(5) A3, Z= 4. zyxw R1 = 0.0435, wR~ = 0.1079. barium; volatile; /I-diketone; X-ray structure INTRODUCTION zyxwv The introduction of ceramic superconducting materials with zyxwvutsrq T, above the temperature of liquid nitrogen has initiated considerable interest in the use of chemical vapour deposition (CVD) for their fabrication, partly because it allows the formation of thin films for hybrid circuit technology and over large areas. For the successful deposition of these (and any other) materials from the gas phase, it is necessary to have precursors for all the elements that are volatile and stable enough to be trans- ported intact to the deposition zone but unstable enough to decompose to the desired material at higher temperatures. For most of the elements required, there is a large number of possible candidate precursors, mainly based on p-diketonates, but for group 2 elements, especially barium, their low group oxidation state (2), large size and ready ability to use low-lying d-orbitals as acceptor orbitals means that they favour high co-ordination numbers and [Ba(TLFND),.tetraglyme] is 2,5,8,1 1,14-pentaoxapentad~anenebis l',l', l', 2', 2', 3', 3', 7',7',8', 8',9',9',9'-tetradecafluorononane- 4',6'-dionato)barium(II). Full bond lengths and angles, atomic co-ordinates, isotropic temperature factors are available from the Cambridge Crystallographic Data Centre. For ordering instructions see Notes for Contributors. t Author to whom correspondence should be addressed. CCC 1057-9257/95/010001-10 zyxwvutsr 0 1995 by John Wiley & Sons, Ltd. Received 11 July 1994 Revised 7 October 1994