Christopher L. Dorsey

Bio: Christopher L. Dorsey is an academic researcher from Texas State University. The author has contributed to research in topics: Carbene & Lewis acids and bases. The author has an hindex of 7, co-authored 13 publications receiving 242 citations. Previous affiliations of Christopher L. Dorsey include Texas A&M University.

Fluoride ion complexation by a B2/Hg heteronuclear tridentate lewis acid

Abstract: The reaction of [Li(THF)4][1,8-μ-(Mes2B)C10H6] with HgCl2 affords [1,1′-(Hg)-[8-(Mes2B)C10H6]2] (3) or [1-(ClHg)-8-(Mes2B)C10H6] (4), depending on the stoichiometry of the reagents. These two new compounds have been characterized by 1H, 13C, 11B and 199Hg NMR, elemental analysis and X-ray crystallography. The cyclic voltammogram of 3 in THF shows two distinct waves observed at E1/2 −2.31 V and −2.61 V, corresponding to the sequential reductions of the two boron centers. Fluoride titration experiments monitored by electrochemistry suggest that 3 binds tightly to one fluoride anion and more loosely to a second one. Theses conclusions have been confirmed by a UV-vis titration experiment which indicates that the first fluoride binding constant (K1) is greater than 108 M−1 while the second (K2) equals 5.2 (± 0.4) × 103 M−1. The fluoride binding properties of 3 have been compared to those of [1-(Me2B)-8-(Mes2B)C10H6] (1) and [1-((2,6-Me2-4-Me2NC6H2)Hg)-8-(Mes2B)C10H6] (2). Both experimental and computational results indicate that its affinity for fluoride anions is comparable to that of 2 but significantly lower than that of the diborane 1. In particular, the fluoride binding constants of 1, 2 and 3 in chloroform are respectively equal to 5.0 (± 0.2) × 105 M−1, 1.0 (± 0.2) × 103 M−1 and 1.7 (± 0.1) × 103 M−1. Determination of the crystal structures of the fluoride adducts [S(NMe2)3][1–μ2-F] and [S(NMe2)3][3–μ2-F] along with computational results indicate that the higher fluoride binding constant of 1 arises from a strong chelate effect involving two fluorophilic boron centers.

Metal‐Free Stabilization of Monomeric Antimony(I): A Carbene‐Supported Stibinidene

Abstract: A diamidocarbene was coordinated to an antimony(III) dichloride Lewis acid. Subsequent reduction with magnesium gave a monomeric, formally antimony(I) fragment that is supported by the diamidocarbene. Spectroscopic, crystallographic, and computational analyses demonstrated that the carbene ligand engages the antimony(I) center in π-backbonding resulting in a short (2.068(7) A) SbC interaction that is comparable to those observed in known stibaalkenes.

Bifunctional Carbenium Dications as Metal-Free Catalysts for the Reduction of Oxygen.

Abstract: The development of catalysts for the oxygen reduction reaction is a coveted objective of relevance to energy research. This study describes a metal-free approach to catalyzing the reduction of O2 into H2O2, based on the use of redox-active carbenium species. The most active catalysts uncovered by these studies are the bifunctional dications 1,8-bis(xanthylium)-biphenylene ([3]2+) and 4,5-bis(xanthylium)-9,9-dimethylxanthene ([4]2+) which promote the reaction when in the presence of decamethylferrocene and methanesulfonic acid. Electrochemical studies carried out with [4]2+ suggest the intermediacy of an organic peroxide that, upon protonation, converts back into the starting dication while also releasing H2O2. Kinetic studies point to the second protonation event as being rate-determining.

Fluoride Ion Complexation and Sensing Using Organoboron Compounds

Abstract: Fluoride is often added to drinking water and toothpaste because of its beneficial effects in dental health. It is also administered in the treatment of osteoporosis.1 While the beneficial effects of fluoride are well documented, chronic exposure to high levels of this anion can lead to dental or even skeletal fluorosis.2-4 Taking into account these adverse effects, a great deal of attention has been devoted to the discovery of improved analytical methods for the detection of fluoride, especially in water. This field of research has also been stimulated by the potential use of such methods for the detection of phosphorofluoridate nerve agents such as Sarin or uranium hexafluoride, which release fluoride upon hydrolysis. In addition to these applications, the capture of fluoride, especially in water, is a stimulating academic challenge because of the high hydration enthalpy of this anion (∆H° ) -504 kJ mol-1). * To whom correspondence should be addressed. E-mail: simon.aldridge@ chem.ox.ac.uk (S.A.) and francois@tamu.edu (F.P.G.). † Texas A&M University. ‡ University of Oxford. Casey Wade was born in 1983 in Lynch, Nebraska. He earned a B.S. degree from the University of NebraskasLincoln in 2006. During his time there, he worked as an undergraduate researcher under the supervision of J. A. Belot and participated in a joint research internship at the American Air Liquide Chicago Research Center. In 2007, he joined the group of F. P. Gabbaı̈ at Texas A&M University, where he currently studies anion recognition using main group Lewis acids.

Cyclic (alkyl)(amino)carbenes (CAACs): stable carbenes on the rise.

Abstract: ConspectusCarbenes are compounds that feature a divalent carbon atom with only six electrons in its valence shell. In the singlet state, they possess a lone pair of electrons and a vacant orbital and therefore exhibit Lewis acidic and Lewis basic properties, which explains their very high reactivity. Following the preparation by our group in 1988 of the first representative, a variety of stable carbenes are now available, the most popular being the cyclic diaminocarbenes.In this Account, we discuss another class of stable cyclic carbenes, namely, cyclic (alkyl)(amino)carbenes (CAACs), in which one of the electronegative and π-donor amino substituents of diaminocarbenes is replaced by a σ-donating but not π-donating alkyl group. As a consequence, CAACs are more nucleophilic (σ-donating) but also more electrophilic (π-accepting) than diaminocarbenes. Additionally, the presence of a quaternary carbon in the position α to the carbene center provides steric environments that differentiate CAACs dramatically fr...

Cyclic (Alkyl)(amino)carbenes (CAACs): Recent Developments

Abstract: Discovered in 2005, cyclic (alkyl)(amino)carbenes (CAACs) are among the most nucleophilic (σ donating) and also electrophilic (π-accepting) stable carbenes known to date. These properties allow them to activate a variety of small molecules and enthalpically strong bonds, to stabilize highly reactive main-group and transition-metal diamagnetic and paramagnetic species, and to bind strongly to metal centers, which gives rise to very robust catalysts. The most important results published up to the end of 2013 are briefly summarized, while the majority of this Review focuses on findings reported within the last three years.

Electronic Properties of N-Heterocyclic Carbenes and Their Experimental Determination

Abstract: N-Heterocyclic carbenes (NHCs) have become without doubt one of the most exciting and popular species in chemical science due to the ease of their preparation and modularity in stereoelectronic properties. Numerous types of NHCs have been prepared, and various experimental methodologies have been proposed for the study of their electronic properties in order to rationalize reactivities observed. The objective of this article is to provide a comprehensive overview of the most common and popular ones among them. In particular, these include the nickel(0)-based TEP, its rhodium(I) and iridium(I) variants, LEP and related electrochemical methods, the palladium(II)-based HEP, phosphinidene- and selenourea-based methods, as well as the use of direct 1J(C–H) coupling constants of the precarbene carbon in azolium salts. Each individual method and the underlying principle of detection it utilizes will be critically discussed in terms of strength and weakness. In addition, comprehensive amounts of data from various...

NHCs in Main Group Chemistry.

Abstract: Since the discovery of the first stable N-heterocyclic carbene (NHC) in the beginning of the 1990s, these divalent carbon species have become a common and available class of compounds, which have found numerous applications in academic and industrial research. Their important role as two-electron donor ligands, especially in transition metal chemistry and catalysis, is difficult to overestimate. In the past decade, there has been tremendous research attention given to the chemistry of low-coordinate main group element compounds. Significant progress has been achieved in stabilization and isolation of such species as Lewis acid/base adducts with highly tunable NHC ligands. This has allowed investigation of numerous novel types of compounds with unique electronic structures and opened new opportunities in the rational design of novel organic catalysts and materials. This Review gives a general overview of this research, basic synthetic approaches, key features of NHC–main group element adducts, and might be...