Elmer O. Schlemper

Bio: Elmer O. Schlemper is an academic researcher from University of Missouri. The author has contributed to research in topics: Crystal structure & Oxime. The author has an hindex of 22, co-authored 89 publications receiving 1134 citations. Previous affiliations of Elmer O. Schlemper include Pontifical Catholic University of Peru.

Synthesis, characterization, and x-ray structural determinations of technetium(V)-oxo-tetradentate amine oxime complexes

Abstract: A number of neutral and lipophilic oxo(L)technetium(V) complexes have been synthesized, where L is a tetradentate amine oxime for which 3,3,9,9-tetramethyl-4,8-diazaundecane-2,10-dione dioxime (Pn(AO)/sub 2/) is the prototype. These TcOL complexes have been characterized by their visible-uv spectra, ir spectra, /sup 1/H and /sup 13/C NMR spectra, fast atom bombardment (FAB) mass spectra, and x-ray diffraction studies. The x-ray crystal structures of four of these complexes show them to be mono(oxo)technetium(V) species with the oxo group situated at the apex of a square pyramid and the technetium lying an average of 0.68 A above the plane defined by the four nitrogen atoms of the tetradentate amine oxime. In each case the tetradentate amine oxime ligand loses three protons on coordination to the technetium(V) center, resulting in an overall charge of zero for the complex, multiple bonding between the amide nitrogens and the technetium, and intramolecular hydrogen bonding between the oxime oxygens. The space constants are reported for the complexes.

.mu.-Oxo-bis(oxo) dinuclear complexes of technetium(V) with amine phenol ligands: syntheses, characterization, and x-ray crystal structures

Abstract: Technetium(V) complexes of three amine phenol ligands prepared by reducing Schiff bases derived from salicylaldehyde and 1,3-diaminopropane, 2,2-dimethyl-1,3-diaminopropane, and 1,4-diaminobutane have been synthesized. {sup 1}H and proton-decoupled {sup 13}C nuclear magnetic resonance spectra of the complexes have been recorded and compared with those of the parent ligands. The complexes have been characterized by infrared spectroscopy, visible-UV spectrophotometry, and x-ray crystallography. X-ray crystal structures show all three complexes are dinuclear with a {mu}-oxo-bis(oxo) (O{double bond}Tc-O-Tc{double bond}O) backbone. The distorted octahedral coordination of Tc(V) is completed by a tetradentate diamine diphenolate ligand. Neutrality of the complexes is achieved by deprotonation of the phenols and by terminal and bridging oxo ligands. The technetium complexes have either a true crystallographic center of symmetry or an approximate center at the bridging oxygen. 16 refs., 4 figs., 10 tabs.

Effect of ring size on properties of technetium amine oxime complexes. X-ray structures of TcO2Pent(AO)2, which contains an unusual eight-membered chelate ring, and of TcOEn(AO)2

Abstract: A series of neutral technetium(V) complexes have been synthesized (TcO(AO)/sub 2/, TcOEn(AO)/sub 2/, TcO/sub 2/Bn(AO)/sub 2/, and TcO/sub 2/Pent(AO)/sub 2/) in which the length of the hydrocarbon backbone of the amine oxime ligand is varied to effect chemical changes in the resultant complexes. Pn(AO)/sub 2/, 3,3,9,9-tetramethyl-4,8-diazaundecane-2,10-dione dioxime, is the prototype for these ligands. In this series of technetium(V) complexes in which the overall ring size is varied, both monooxo and trans-dioxo cores are observed, and an unusual eight-member chelate ring with the technetium(V) center is found with TcO/sub 2/Pent(AO)/sub 2/. TcO/sub 2/Pent(AO)/sub 2/ x CHCl/sub 3/, TcCl/sub 6/O/sub 4/C/sub 17/H/sub 33/, crystallizes in the triclinic system, space group P anti 1, with a = 1.418 (2) A, b = 13.940 (7) A, c = 18.992 (10) A, ..cap alpha.. = 69.29 (4)/sup 0/, ..beta.. = 90.00 (3)/sup 0/, ..gamma.. = 83.69 (3)/sup 0/, and Z = 4. TcOEn(AO)/sub 2/, TcO/sub 3/N/sub 4/C/sub 12/H/sub 23/, crystallizes in the orthorhombic system, space group Pbca, with a = 11.581 (2) A, b = 12.596 (4) A, c = 21.155 (3) A, and Z = 8.

The crystal chemistry of hexavalent uranium; polyhedron geometries, bond-valence parameters, and polymerization of polyhedra

Abstract: The geomeffy, bond valences, and polymerization ofhexavalent uranium polyhedra from 105 well-refined structures are analyzed. The Utu cation is almost always present in crystal stnrctures as part of a nearly linear (UOr)z* uranyl ion that is coordinated by four, five or six equatorial anions in an approximately planar arangement perpendicular to the uranyl ion, giving square, pentagonal and hexagonal bipyramids, respectively. The Utu-O7\" bond length (Oy,: uranyl-ion O atom) is independent of the equatorial anions of the polyhedra;-averages of all polyhedra tlat contain uranyl ions ffs; I6lIJ6f-Or. = 1.79(3), mg0.-.9 a,= 1.79(4), and t8lu6+-Our = 1.78(3) A. Not a[ r6lu6+ polyhedra contain uranyl ions; there is a continuous series of coordiaation polyhedr4 from square bipyramidal polyhedra with uranyl ions to holosymmehic octahedral geometry. The mUo* and t8lu6+ polyhedra invariably contaitl a uranyl ion. The equatorial U6.-0 (0: O,-, OH-) bond-lengths of uranyl polyhedra depend upon coordhation number; averages for all polyhedra are t6lu6+-dq = 2,28(5), rlUot-$* = 2.37(9), afi t8tlJ6+-$q2.47 (12) A. Cunently available bond-valence parameters for U& are unsatisfactory for determining bond-valence sums. Coordination-specific bond-valence paxameters have been derived for U6|, together with parameters applicable to all coordination geometries. The parameters give bond-valence sums for Ue of -6 vlr and reasonable bond-valences for Uc,-Ou, bonds. The bond-valence paraneters facilitate the recognition of Ua, U5+ and U6| catiotrs in refined crystal structures. The crystal-chemical consfraints ofpolyhedral polymerization in uranyl phases are discussed.

International Tables for X-Ray Crystallography

Abstract: International Tables for X-Ray Crystallography (Published for the International Union of Crystallography.) Vol. 1: Symmetry Groups. Edited by Norman F. M. Henry and Kathleen Lonsdale. Pp. xi + 558. (Birmingham: Kynoch Press, 1952.) 105s.

U6+ minerals and inorganic compounds: insights into an expanded structural hierarchy of crystal structures

Abstract: The crystal structures of uranyl minerals and inorganic uranyl compounds are important for understanding the genesis of U deposits, the interaction of U mine and mill tailings with the environment, transport of actinides in soils and the vadose zone, the performance of geological repositories for nuclear waste, and for the development of advanced materials with novel applications. Over the past decade, the number of inorganic uranyl compounds (including minerals) with known structures has more than doubled, and reconsideration of the structural hierarchy of uranyl compounds is warranted. Here, 368 inorganic crystal structures that contain essential U6+ are considered (of which 89 are minerals). They are arranged on the basis of the topological details of their structural units, which are formed by the polymerization of polyhedra containing higher-valence cations. Overarching structural categories correspond to those based upon isolated polyhedra (8), finite clusters (43), chains (57), sheets (204), and frameworks (56) of polyhedra. Within these categories, structures are organized and compared upon the basis of either their graphical representations, or in the case of sheets involving sharing of edges of polyhedra, upon the topological arrangement of anions within the sheets.

Structure and Mineralogy of Clay Minerals

Abstract: Phyllosilicates, and among them clay minerals, are of great interest not only for the scientific community but also for their potential applications in many novel and advanced areas. However, the correct application of these minerals requires a thorough knowledge of their crystal chemical properties. This chapter provides crystal chemical and structural details related to phyllosilicates and describes the fundamental features leading to their different behaviour in different natural or technical processes, as also detailed in other chapters of this book. Phyllosilicates, described in this chapter, are minerals of the (i) kaolin-serpentine group (e.g. kaolinite, dickite, nacrite, halloysite, hisingerite, lizardite, antigorite, chrysotile, amesite, carlosturanite, greenalite); (ii) talc and pyrophyllite group (e.g. pyrophyllite, ferripyrophyllite); (iii) mica group, with particular focus to illite; (iv) smectite group (e.g. montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite); (v) vermiculite group; (vi) chlorite group; (vii) some 2:1 layer silicates involving a discontinuous octahedral sheet and a modulated tetrahedral sheet such as kalifersite, palygorskite and sepiolite; (viii) allophane and imogolite and (ix) mixed layer structures with particular focus on illite-smectite.