Part I. Clathrasil chemistry: Synthesis and characterization of dodecasil-3C and dodecasil-1H clathrasils. Part II. Synthesis and structure of pentamethylcyclopentadienyl rhodium vanadium and molybdenum oxides

Chae, Hee Kwon

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Description

Title

Part I. Clathrasil chemistry: Synthesis and characterization of dodecasil-3C and dodecasil-1H clathrasils. Part II. Synthesis and structure of pentamethylcyclopentadienyl rhodium vanadium and molybdenum oxides

Author(s)

Chae, Hee Kwon

Issue Date

1991

Doctoral Committee Chair(s)

Klemperer, Walter G.

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Chemistry, Inorganic
• Engineering, Materials Science

Language

eng

Abstract

• Part I. Hydrothermal methods were developed for the growth of mm-sized crystals of dodecasil-3C clathrasils, 17 SiO$\sb2\cdot$M (M = pyridine, cyclopentane, cyclohexane, piperidine, pyrrolidine, cyclopentylamine, and cyclobutylamine). Reaction conditions were optimized for large, chemically pure dodecasil-3C (D3C) crystals. For the synthesis of pyridine, cyclopentane, and cyclohexane D3C crystals, an aqueous pyridinium bifluoride solution was used as a catalyst. Phase transformations of pyridine D3C crystals were determined by differential scanning calorimetry to commence at 161$\sp\circ$C and $-$46$\sp\circ$C on cooling. The crystal structure of the ambient temperature tetragonal 17 $\rm SiO\sb2{\cdot}C\sb5H\sb5N$ phase was determined using single crystal X-ray diffraction techniques which revealed that the Py-D3C crystals were acentric at ambient temperature and thus second harmonic generators. All other clathrasils synthesized were also tetragonal at ambient temperature, and underwent a transformation to a cubic phase at elevated temperatures, as well as a transformation to a lower symmetry phase at lower temperatures. The size of the guest molecule had a large influence on the phase transition temperatures, with larger guest molecules raising the temperature of the high temperature transition and lowering the temperature of the lower temperature transition. The methodology for synthesizing large D3C crystals was applied to form the dodecasil-1H (D1H) phase with adamantane.
• Part II. The reaction of (($\rm C\sb5 Me\sb5)Rh(OH)\sb2\rbrack \sb2$ with $\rm V\sb2O\sb5$ in water has yielded ($\rm (C\sb5Me\sb5)Rh\rbrack \sb4 (V\sb6O\sb{19})$ (1). The crystal structure of 1, determined by Dr. Victor Day at Crystalytics Company in Lincoln, NE, revealed the presence of a neutral complex in which four Cp*Rh$\sp{2+}$ cations are bound to a single $\rm V\sb6O\sb{19}\sp{8-}$ anion. This approach can be extended to the synthesis of $\{\lbrack \rm(C\sb5Me\sb5)Rh\rbrack \sb8Mo\sb{13}O\sb{40}\}Cl\sb2$ (2) by the hydrothermal reaction of (($\rm Cp*Rh)\sb2 (OH)\sb3\rbrack Cl$ with MoO$\sb3 \cdot$2H$\sb2$O. In this crystal structure, each of the eight Cp*Rh$\sp{2+}$ cations is bound to three of the twenty-four doubly bridging oxygens of a Mo$\rm\sb{13}O\sb{40}\sp{14-}$ anion. The Mo$\rm\sb{13}O\sb{40}\sp{14-}$ core was determined to be an $\varepsilon$-Keggin isomer.

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text

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Copyright 1991 Chae, Hee Kwon

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