On the coordination chemistry of pentavalent (σ⁴, λ⁵) phosphorus compounds

Macor, Joseph Alexander

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Description

Title

On the coordination chemistry of pentavalent (σ⁴, λ⁵) phosphorus compounds

Author(s)

Macor, Joseph Alexander

Issue Date

2015-04-20

Director of Research (if dissertation) or Advisor (if thesis)

Girolami, Gregory S.

Doctoral Committee Chair(s)

Girolami, Gregory S.

Committee Member(s)

• Denmark, Scott E.
• Fout, Alison R.
• Lu, Yi

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Asymmetric Synthesis
• Minor Actinide Separations
• Heterogeneous Asymmetric Catalysis

Abstract

The work described herein details the synthesis of a variety of pentavalent organophosphorus compounds and their applications as ligands to address important problems in coordination chemistry. This research encompasses two main themes: (1) the asymmetric synthesis of enantiopure α-alkylbenzylphosphonic acids, and the use of these compounds to prepare homochiral vanadium diphosphonate materials that can serve as heterogeneous catalysts for the asymmetric epoxidation of allylic alcohols, and (2) the design and synthesis of novel heterocyclic dithiophosphinic acids and exploration of their coordination chemistry with the f-elements, with the ultimate goal of better understanding the properties that dictate selectivity in Ln/An extractions in the context of nuclear fuel reprocessing. Enantiopure (R)-BINOLato benzylphosphonate is easily and inexpensively prepared, and is stable to air and moisture. Deprotonation with n-butyllithium followed by addition of a methyl, ethyl, allyl, or benzyl halide electrophile at -78 °C affords (R)-BINOLato (R)-1-alkylbenzylphosphonates in good yields and excellent diastereoselectivities. Removal of the chiral auxiliary is best accomplished in a two step procedure: cesium fluoride promoted transesterification to the dimethyl phosphonate ester, followed by acidic hydrolysis to the corresponding phosphonic acid. This sequence affords (R)-1-alkylbenzyl-phosphonic acids in high yield and optical purity. This technique can be extended to the synthesis of chiral diphosphonic acids containing naphthalene backbones. These ligands, along with their achiral analogues, react with VO2+ to generate vanadyl diphosphonate materials. These products are insoluble in organic solvents and have a layered architecture as judged by powder X-ray diffraction. These compounds are the first examples of homochiral polymers containing diphosphonate linkages, and exhibit exceptional catalytic activity for the heterogeneous chemoselective epoxidation of allylic alcohols when tert-butyl hydroperoxide is employed as a stoichiometric oxidant. With the homochiral catalysts, the enantioselectivity is modest, but apparent (e.r. ≈ 3:2). Synthetic methodology has also been developed that affords novel heterocyclic 2,2ʹ-biphenylenedithiophosphinic acids, which contain 5-membered dibenzophosphole rings. These new compounds have been fully characterized by conventional techniques, as well as by K-edge X-ray absorption spectroscopy in order to elucidate the electronic consequence of rotational restriction about the P–Cipso bonds. Liquid/liquid extraction studies show that these compounds exhibit a ca. 10:1 selectivity for the preferential chelation of 241Am over 154Eu. In addition, homoleptic complexes of Eu3+, Nd3+, U4+, and Np4+ with the 2,2ʹ-biphenylenedithiophosphinate ligand have been prepared and characterized by single crystal X-ray diffraction.

Graduation Semester

2015-5

Type of Resource

text

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Copyright and License Information

Copyright 2015 Joseph Alexander Macor

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