Synthesis and Characterization of Heterobimetallic Alkaline Earth Metal Amides

Master's Thesis
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Abstract

The synthesis and characterization of heterobimetallic alkaline-earth metal amides was attempted. This is an entirely new class of compounds and they were targeted with the purpose of evaluating their bond character aggregation behavior in solution and in the solid state. The reaction between the appropriate homometallic bis(hexamethyldisilazide) precursors in non-donating solvents yielded the products: CaMg{N(SiMe3)2}4, SrMg{N(SiMe3)2}4, SrCa{N(SiMe3)2}4, and [Ba2{N(SiMe3)2}3"¢toluene]+[Mg{N(SiMe3)2}3]- (4). The synthesis of crystalline Ba/Ca and Ba/Sr heterobimetallic complexes was attempted however they do not mix in solution. Compounds 1-4 were successfully characterized by single crystal X-ray diffraction. Structures 1, 2, and 3 are all heterodimers with a four membered ring core consisting of both metals connected by bridging amide groups. Each metal is bonded to a single amide group yielding a coordination number of three. The charge separated complex 4 consists of a magnesium trisamide anion and a dimeric barium cation with one metal site solvated by a π-bound toluene molecule. Analysis of the metrical parameters in 1-3 indicates that the more Lewis acidic metal pulls the electron density of the bridging amide ligands towards it, causing a Lauren T. Wendell

change in the bonding when compared to the homodimer structures. This change in the bonding causes interesting solution behavior, where charge separated species are often seen in donating solvents. The most extreme case is complex 4 where charge separation is also observed in the solid state. Complexes 1, 2, and 3 all undergo a dynamic equilibrium between the heterobimetallic structures and the homometallic precursors in arene solvents. In contrast, Complex 4 maintains charge separation. The change in the bonding and solution behavior compared to the homodimers suggests that these compounds will have interesting reactivity with organic substrates.

Attributes

Attribute NameValues
URN
  • etd-09202005-093844

Author Lauren Theresa Wendell
Advisor Marya Lieberman
Contributor Marya Lieberman, Committee Member
Contributor Olaf Wiest, Committee Member
Degree Level Master's Thesis
Degree Discipline Chemistry and Biochemistry
Degree Name MS
Defense Date
  • 2005-09-19

Submission Date 2005-09-20
Country
  • United States of America

Subject
  • Metal Amides

  • Alkaline Earth Metals

Publisher
  • University of Notre Dame

Language
  • English

Record Visibility and Access Public
Content License
  • All rights reserved

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