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Synthesis, Structure, and Reactivity of High Oxidation State Silver Fluorides and Related Compounds

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LBL-37334 UC-40 1 . Synthesis, Structure, and Reactivity of High Oxidation 1 State Silver Fluorides and Related Compounds George Michael Lucier Ph.D. Thesis Department of Chemistry University of California, Berkeley and Chemical Sciences Division Lawrence Berkeley Laboratory University of California Berkeley, CA 94720 May 1995 2 I This work was Supportedsupported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division, of the U.S. Department of Energy under Contract No. DE-ACO3-76SFooo98.DE-ACO3-76SFOOO98. JNLIMIED $ D\STRIBUT(ON OF THIS is UNLIMIED DISC LA1M E R This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. Synthesis, Structure, and Reactivity of High Oxidation State Silver Fluorides and Related Compounds George Michael Lucier B.S. (Stanford University) 1990 A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Chemistry in the GRADUATE DIVISION of the UNIVERSITY of CALIFORNIA at BERKELEY Committee in charge: Professor Neil Bartlett, Chair Professor Angelica Stacy Professor Alex Zettl 1995 1 Abstract Synthesis, Structure, and Reactivity of High Oxidation State Silver Fluorides and Related Compounds . by George Michael Lucier Doctor of Philosophy in Chemistry University of California at Berkeley Professor Neil Bartlett, Chair The research described in this thesis has been largely concerned with defining the oxidizing power of Ag(II1) and Ag(I1) species in anhydrous hydrogen fluoride (aHF) solution. Emphasis has been placed on the study of cationic species, since in a cation the electronegativity of a given oxidation state is greater than in the neutral or anionic 111 relatives. Cationic Ag solv has a short half life at ordinary temperatures, oxidizing the solvent to elemental fluorine with formation of Ag(I1). Salts of such a cation have not yet been preparable, but solutions which must contain such a species have proved to be 111 effective and powerful oxidizers. In the presence of PtF,, RuF,, or RhF,, Ag solv effectively oxidizes the anions to release the neutral hexafluorides. Such reactivity ranks ‘L cationic Ag(II1) as the most powerfully oxidizing chemical agent known so far. I1 Unlike its trivalent relative, Ag solv is thermodynamically stable in acid aHF. Nevertheless, it has been observed to oxidize IrF, to IrF, at room temperature, placing its 2 oxidizing poteqtial not more than 2 eV below that of cationic Ag(II1). The range of Ag2'(MF& salts attainable in aHF has been explored. An anion must be stable with respect to loss of its electron to Ag2+. The anion must also be a poor F- donor; otherwise, either AgF' salts or AgF2 are generated. A general method for the synthesis of AgF'MF, salts has been found in which Ag+MF, salts are fluorinated in aHF. AgFIrF6 is preparable, but AgFOsF6 is not, placing the oxidizing potential of the polymeric fluorine-bridged (AgF):' cation -1 eV lower than I1 that of Ag solv. The AgF'MF, salts have been found to adopt at least three different structure types, ranging from monoclinic to tetragonal symmetry. The structures of AgF'BF, and AgF+IrF, reveal a polymeric chain cation of formula (AgF)",' in which the Ag(I1) is linearly coordinated. A second AgF'MF, structure type occurs in AgF'RuF,, which exhibits square coordination of the cation, generating a one-dimensional ribbon. The AgF'MF; (M = Sb, Si) represent yet another structure type (based on X-ray powder data), but the atomic arrangement is not yet known. All AgF' salts examined exhibit a small temperature-independent paramagnetism indicative of a metallic band structure (i. e. Pauli paramagnetism). Polarized light transmission experiments on single crystals of AgFBF4 support the hypothesis that these salts are one-dimensional metals, but no direct evidence for electronic conductivity has been found. ... 111 Synthesis. Structure. and Reactivity of High Oxidation State Silver Fluorides and Related Compounds Table of Contents 1. Chapter 1 Introduction and Experimental Considerations .................................... 1 1.1. General Introduction............................................................................................ 1 1.2. Electron Affinities of Third Row Transition Metal Hexafluorides ..................... 3 1.3. Relative Fluoride Ion Affinities of Some Fluoro-acids ....................................... 5 1.3.1 . Fluoro-acidity Ranking of Main Group Fluorides .................................. 6 1.4. Stabilization of High Oxidation State Cations Such as AgF? ............................ 9 1.5. References ......................................................................................................... 10 2 .Chapter 2 Experimental Methods ........................................................................... 12 2.1 . Apparatus ........................................................................................................... 12 2.2. Characterization Techniques ............................................................................. 13 2.2.1. X-ray Powder Diffraction ..................................................................... 13 2.2.2. Single Crystal X-ray Diffraction ........................................................... 14 2.2.3. SQUID Magnetometry .......................................................................... 14 2.3. Anhydrous HF as an Oxidatively Inert Solvent ................................................ 14 2.4. Reaction Technique ........................................................................................... 16 2.5. References ......................................................................................................... 19 3 . Chapter 3 Preparation of Reagent Materials ......................................................... 20 iv 3.1. Introduction ....................................................................................................... 20 3.2. Commercially Available Reagents .................................................................... 21 3.3. Preparation of IrF, and IrF6............................................................................... 21 . -k + 3.4. Preparation of SF3 OsF, and SF3 IrF, .............................................................. 22 3.5. Preparation of AMF6 salts ................................................................................. 24 3.5.1. Synthesis ofLiP@, and UtF6fiom O”,PtF, ........................................ 24 3.5.2. Preparation of LiRuFs ........................................................................... 26 3.5.3. General Synthesis of AMF6 from AF and MF, .................................... 26 3.6. References ......................................................................................................... 31 4. Chapter 4 The Oxidizing Chemistry of Solvated A$’.......................................... 32 4.1. Introduction ....................................................................................................... 32 4.2. Experimental ..................................................................................................... 34 4.2.1 . Preparation of AMF, ............................................................................ -34 4.2.2. Preparation of KAgF4 ........................................................................... 35 4.2.3. Preparation of AgF, .............................................................................. 36 4.2.4. Oxidation of RuF, ................................................................................. 37 4.2.5. Oxidation of RhF, ................................................................................. 38 4.2.6. Oxidation of PtF, .................................................................................. 39 4.2.6.1. Using KPtF, as a Reagent ........................................................ 39 4.2.6.2. Using LiPtF6 as a Reagent ....................................................... 40 V 4.2.7. Attempted Oxidation of AuFi ............................................................... 41 4.3. Results and Discussion ...................................................................................... 42 4.4. Conclusions ....................................................................................................... 45 4.5. References ......................................................................................................... 46 5. Chapter 5 Synthesis and Oxidizing Properties of AgF+ Salts ............................... 47 5.1. Introduction ......................................................................................................
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