The design and synthesis of novel chelates for the precipitation

University of Kentucky UKnowledge University of Kentucky Doctoral Dissertations Graduate School 2007 THE DESIGN AND SYNTHESIS OF NOVEL CHELATES FOR THE PRECIPITATION OF MERCURY Aaron Robert Hutchison University of Kentucky, ahutchinson@cedarville.edu Right click to open a feedback form in a new tab to let us know how this document benefits you. Recommended Citation Hutchison, Aaron Robert, "THE DESIGN AND SYNTHESIS OF NOVEL CHELATES FOR THE PRECIPITATION OF MERCURY" (2007). University of Kentucky Doctoral Dissertations.edu/gradschool_diss/519 This Dissertation is brought to you for free and open access by the Graduate School at UKnowledge. It has been accepted for inclusion in University of Kentucky Doctoral Dissertations by an authorized administrator of UKnowledge.

For more information, please contact UKnowledge@lsv. ABSTRACT OF DISSERTATION Aaron Robert Hutchison The Graduate School University of Kentucky 2007 THE DESIGN AND SYNTHESIS OF NOVEL CHELATES FOR THE PRECIPITATION OF MERCURY _______________________________ ABSTRACT OF DISSERTATION ________________________________ A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Arts and Sciences at the University of Kentucky By Aaron Robert Hutchison Lexington, Kentucky Director: Dr. David Atwood, Associate Professor of Chemistry Lexington, Kentucky 2007 Copyright © Aaron Robert Hutchison 2007 ABSTRACT OF DISSERTATION THE DESIGN AND SYNTHESIS OF NOVEL CHELATES FOR THE PRECIPITATION OF MERCURY Mercury has been an element of great industrial importance since early times. This wide utilization of the element has led to pervasive mercury contamination in the global environment.

Due to mercury’s high toxicity, this is a matter of great concern. A number of methods, includ ing phytoremediation, filtration, and precipitation/chelation, have been investigated to remove mercury from the environment. Unfortunately, these methods are not entirely satisfactory for the in-situ remediation of mercury from aqueous environments. The hypothesis of this dissertation is that this can best be accomplished by the addition of a large and flexible sulfur-based chelate, that will bind mercury in a tetracoordinate and presumably tetrahedral environment, to mercury-contaminated waters.

Although this proved difficult due to the tendency of these ligands to decompose into smaller, sulfur-containing rings, the synthesis and characterization of such a chelate was achieved. Several potential mercury-binding ligands were eventually synthesized significant amounts of mercury (91-100%) from the contaminated solutions, in one case lowering the mercury levels in the water to below the CVAF detection limits. The resulting solids lost little (<15 ppb) of their mercury during leaching studies. This work demonstrates the use of tetradentate chelates in precipating Hg2+ from water to produce stable mercury- ligand precipitates.

A calculation for the quantification of the geometry of a four-coordinate compound was also developed and applied to aluminum, gallium, and mercury compounds. This calculation could also be applied to the mercury compounds described in this thesis once X-ray structures become available KEYWORDS: Mercury, Remediation, Thiols, Chelation, Precipitation Aaron Hutchison February 26, 2007 THE DESIGN AND SYNTHESIS OF NOVEL CHELATES FOR THE PRECIPITATION OF MERCURY By Aaron Robert Hutchison Dr. David Atwood Director of Dissertation Dr. Robert Grossman Director of Graduate Studies February 26, 2007 RULES FOR THE USE OF DISSERTATIONS Unpublished dissertations submitted for the Doctor's degree and deposited in the University of Kentucky Library are as a rule open for inspection, but are to be used only with due regard to the rights of the authors.

Bibliographical references may be noted, but quotations or summaries of parts may be published only with the permission of the author, and with the usual scholarly acknowledgments. Extensive copying or publication of the dissertation in whole or in part also requires the consent of the Dean of the Graduate School of the University of Kentucky. A library that borrows this dissertation for use by its patrons is expected to secure the signature of each user. DISSERTATION Aaron Robert Hutchison The Graduate School University of Kentucky 2007 THE DESIGN AND SYNTHESIS OF NOVEL CHELATES FOR THE PRECIPITATION OF MERCURY ___________________________________ DISSERTATION ___________________________________ A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Arts and Sciences at the University of Kentucky By Aaron Robert Hutchison South Charleston, Ohio Director: Dr.

David Atwood, Associate Professor of Chemistry Lexington, Kentucky 2007 Copyright © Aaron Robert Hutchison 2007 This work is dedicated to my parents and friends for all their support during my research. It is also dedicated to God, from Whom all human originality and success originate. ACKNOWLEDGEMENTS The following dissertation, while representing my individual work, has been strengthened by the input of several individuals. First, I would like to thank my advisor, Dr.

David Atwood, for his encouragement and support during my graduate career. I would also like to thank several other past and present members of the Atwood research group, including Dr. Sonali Bhandari, Dr. Burl Yearwood, Dr.

Tim Keizer, Mr. Niladri Gupta, Mr. Taimur Shaikh, Mr. John Twyman, and Mr.

Eduardo Santillion, for their advice and assistance during various stages of this work. Next, I would to thank my Dissertation Committee and outside examiner, Dr. John Selegue, Dr. Folami Ladipo, Dr.

Robert Grossman, Dr. Chris Matocha, and Dr. Dibakar Bhattacharyya for their help at every stage of this process. In addition to the professional assistance given by those listed above, throughout my work I received personal support from a network of friends too numerous to list individually.

Specifically, I would like to acknowledge my many friends at Porter Memorial Baptist Church, Highlands Baptist Church, and Zion Baptist Church for their care for me during this process. I would also like to thank my mother and father, John and Teresa Hutchison, witho ut whose help I never could have completed this project. iii TABLE OF CONTENTS Acknowledgements………………………………………………………………………iii List of Tables…………………………………………………………………………….vi List of Figures……………………………………………………………………………vii List of Files…………………………………………………………………………….viii Chapter One: Mercury Pollution and Remediation………………………………………1 1.2 Methylmercury and Human Mercury Poisoning ………………………….3 Industrial Uses of Mercury………………………………………………….4 Environmental Mercury Pollution………………………………………….1 Remediation of Mercury from the Gas Phase……………………26 1.2 Remediation of Mercury from Water and Soil……………….1 Excavation and Capping….3 Phytoremediation and Bioremediation………………….5 Complexation and Ultrafiltration……………………….6 Precipitation and Extraction…………………………….8 Mercury Precipitation Research in the Atwood Group…………………….9 The Design of an Ideal Mercury Precipitation Agent……….52 Chapter Two: Non-Thiol Ligand Byproducts of the Project…………………………….1 An Introduction to Sulfur…………………………………………………….4 Alkyl Sulfide Ligands…………………………………………………….79 Chapter Three: Synthesis and Application of the Thiol Ligands……………………….1 The Synthesis of 3S4SH and 4S4SH………………………………….2 The Use of the New Thiol Ligands in Mercury Precipitation…………….102 iv Chapter Four: A Quantification of Geometry for Four-Coordinate Aluminum and Gallium……………………………………………………………………………….1 The Four-Coordinate Geometric Parameter………….2 Application of the Parameter to Group 13 Structures…………………….3 Application of the Parameter to Mercury Structures……………………….133 Chapter Five: Conclusions and Further Work…………………………………………134 5.1 Conclus ions and Further Work…………………………………………….153 v LIST OF TABLES Table 3.1 The removal of mercury from water by the new thiols………………….2 Results of the leaching study.1 Geometric data for all examples……………………………….116 vi LIST OF FIGURES Figure 1.3 Chelation therapy ligands……………………………………………………10 Figure 1.4 The geochemical mercury cycle………………………………………….5 Mercury deposition as recorded by the Upper Fremont Glacier since 1750.6 Commercial remediation agents…….7 Representative TMT titration curve…………………………………………47 Figure 1.8 Fractional composit ion of TMT by pH…………………………………….9 Target ligands for the ideal mercury precipitation chelate….1 Rosen and Busch’s synthesis of 3S2SH …………………………………….2 Some new dithioether diols…………………….3 Proposed structure for 4S2-tert-OAlCH3 ……………………………………63 Figure 2.4 The diene route………………………………………….5 Some new dithioether dienes……………………………………………….6 The reaction of 2O2S3diene and tin chloride ……………………………….7 The tin dithioether diene dimer…………….8 The cyclization of an “arm”…………………………………….9 The tert-butyl route…………………………………………….1 Direct halide substitution plan …….2 Summary of direct substitution reactions attempted……………………….3 Results of Ochrymowycz’s study of crown thioether synthesis …………….4 Possible mechanism for the failure of the sodium salt SN2 reactions …….5 The cesium route………………………………………………………….6 Ligands analyzed for mercury removal…………………………………….1 One face of a tetrahedron……………………………………….2 The Four Coordinate Geometric Parameter…………………………….7 Ko and Kang’s structure………………………………………………….130 vii LIST OF FILES ARHdissertation.04 MB viii Chapter One: Mercury Pollution and Remediation 1.1 Mercury Mercury is an unusual element, noteworthy both for its liquid state (m.9°C) and high vapor pressure at room temperature (1.1 It also has the property of dissolving some metals to form amalgams. Due to this property, mercury is believed to have been used to extract gold, silver, and other metals from ore through amalgamation since as early as 2700 BC,2 a practice that continues into the present.

In nature, mercury is most often found as the reddish mineral cinnabar (HgS). Large deposits of cinnabar have been located and mined in Spain, the former Soviet Union, Yugoslavia, Mexico, Italy, North Africa, and California, with by far the largest deposit being at Almaden, Spain. Elemental mercury can be easily isolated from cinnabar by roasting. 1 Mercury has an electron configuration of [Xe]4f14 5d10 6s2.

It is unique in that it is the only element outside of the noble gases to give off a monatomic vapor. It also has a high electrical resistivity. 1 Some of its unusual properties are due to the high relativistic effects experienced for mercury; the speed of its 1s electrons is greater than half the speed of light, leading to a contraction of the s and p orbitals and, due to greater shielding by the contracted orbitals, an expansion of the d and f orbitals.3 This results in a net contraction of the overall atom and is largely responsible for the greater electronegativity seen in such large elements. Mercury exists in three forms, elemental Hg0 , monovalent HgI-HgI (Hg2 II), and divalent HgII.

Of these, it is interesting to note that the monovalent oxidation state is only found as bimetallic HgI-HgI, never as the monatomic HgI ion. Furthermore, this oxidation state is significantly less common than the elemental and divalent states. Mercury also shows a distinct tendency to form strong 1 bonds with sulfur, to the extent that thiol compounds are sometimes known as mercaptans, from the Latin mercurium captans “mercury seizing”.4 This can at least partially be explained by the hard soft acid base (HSAB) concept. Sulfur is a quintessential soft base and HgII is one of the best examples of a soft acid.

It has even been argued that the methylmercury ion serves as the “soft” equivalent of the “hard” proton. 5 Therefore, it is expected that combinations of mercury and sulfur-containing species would form stable compounds. Due to its soft nature, mercury is usually considered to more readily form covalent bonds with ligands than many metals. 1 Mercury has long fascinated chemists due to its unusual properties.

Mercury and sulfur (another element central to this study, which will be discussed in greater length later) were key reagents for the early alchemists and were utilized in pursuit of the transmutation of base materials to gold as early as 100 AD. In ancient China, mercury was used medicinally to kill lice and fleas. It was also given to patients in supposedly health-promoting elixirs, a practice which led to the death of at least three Chinese emperors.6 Even though the emperors died, the Chinese alchemists considered the experiments at least partial successes, since decomposition was delayed in these victims. In reality, the highly toxic mercury compounds had killed all the microbial organisms in the body, along with the patient, thus delaying the onset of decay.

The early European doctor Paracelsus used mercury to treat syphilis, a dubious practice that was continued until the twentieth century. 6 More positively, Lavoisier utilized mercuric oxide as his oxygen source dur ing his groundbreaking study of the element.7 Mercury has remained an element of interest for chemists on into modern times. In the mid-1990’s, a pair of structural reviews were published covering the coordination8 and organometallic compounds9 of mercury. Virtually all of the compounds found in both studies involved the divalent oxidation state.

Among the coordination compounds, the most common coordination number was four and the most common geometry tetrahedral, with varying degrees 2 of distortion. This was usually achieved by using four monodentate ligands or two bidentate ligands, rather than a single tetradentate ligand such as is the focus of the present study. For the organomercury compounds, however, a two-coordinate linear arrangement was overwhelmingly the most commom motif.