title: Syntheses of the Uranium Complexes [U{N(SiMe(3))(2)}(2){N(SiMe(3))(SiMe(2)CH(2)B(C(6)F(5))(3))}] and [U{C(Ph)(NSiMe(3))(2)}(2){&mgr;(3)-BH(4)}(2)]. Determination of Hydrogen Positions by Single-Crystal X-ray and Neutron Diffraction.
abstract: The complex [U{N(SiMe(3))(2)}(2){N(SiMe(3))(SiMe(2)CH(2)B(C(6)F(5))(3))}] (1) is formed in the reaction between the hydride complex [U{N(SiMe(3))(2)}(3)(H)] and B(C(6)F(5))(3), and H(2) is evolved. The X-ray [C(36)H(53)BF(15)N(3)Si(6)U.3.5C(6)D(6), triclinic, space group P&onemacr;, Z = 2, 90 K, a = 14.065(1) Å, b = 14.496(1) Å, c = 18.759(1) Å, alpha = 82.898(1) degrees, beta = 74.415(1) degrees, gamma = 62.919(1) degrees ] and neutron structure [C(36)H(53)BF(15)N(3)Si(6)U.3.5C(6)D(6), triclinic, space group P&onemacr;, Z = 2, 20 K, a = 13.993(1) Å, b = 14.484(1) Å, c = 18.720(1) Å, alpha = 82.810(1) degrees, beta = 74.200(1) degrees, gamma = 63.054(1)E] of compound 1, which crystallizes with 3.5 molecules of C(6)D(6) per asymmetric unit, show the electron deficiency of the uranium atom to be effectively compensated by the formation of multicenter bonds between U and three Si-CH(2) units of the amido ligands. The reaction of the uranium complex [U{C(Ph)(NSiMe(3))(2)}(2)(Cl)(2)] with [Na(BH(4))] gives the complex [U{C(Ph)(NSiMe(3))(2)}(2){&mgr;(3)-BH(4)}(2)] (2). The X-ray structure of 2 [C(26)H(54)B(2)N(4)Si(4)U, monoclinic, space group C2/c, Z = 4, 90 K, a = 21.613(1) Å, b = 9.233(1) Å, c = 18.132(1) Å, beta = 98.804(1) degrees ] proves unequivocally the &mgr;(3) coordination of the BH(4) moieties. In both single-crystal X-ray structure determinations, all hydrogen and deuterium atoms could be located and isotropically refined, including those which are directly coordinated to the uranium. The reliability of the refined hydrogen and deuterium positions for compound 1 is confirmed by comparison of the X-ray and neutron structure determinations. The ability to locate the hydrogen and deuterium positions in these uranium compounds by single-crystal X-ray diffraction is due to good crystal quality, the measurement of data at low temperature, and the use of image plate technology for data collection.
authors.affiliation: Chemical Crystallography Laboratory, University of Oxford, 9 Parks Road, Oxford OX1 3PD, U.K., Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France, and Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K.
authors.forename: Matthias
authors.initials: M
authors.lastname: Müller
authors.forename: V. Cliff
authors.initials: VC
authors.lastname: Williams
authors.forename: Linda H.
authors.initials: LH
authors.lastname: Doerrer
authors.forename: Michael A.
authors.initials: MA
authors.lastname: Leech
authors.forename: Sax A.
authors.initials: SA
authors.lastname: Mason
authors.forename: Malcolm L. H.
authors.initials: ML
authors.lastname: Green
authors.forename: Keith
authors.initials: K
authors.lastname: Prout