Cyclometalated phosphine-based pincer complexes: Mechanistic insight in catalysis, coordination, and bond activation

One of the initial steps in the development of therapeutic agents is the identification of lead compounds that bind to the receptor or enzyme target of interest. Many analogs of these lead compounds are then synthesized to define the key recognition elements for maximal activity. In general, many compounds must be evaluated in both the lead identification and optimization steps. Increasing burdens have been placed on these efforts due to the large number of new therapeutic targets that continue to be identified thorough modern molecular biology methods.1 To address this demand, very powerful chemical and biological methods have been developed for the generation of large combinatorial libraries of peptides2 and oligonucleotides3 that are then screened against a receptor or enzyme to identify high-affinity ligands or potent inhibitors, respectively. While these studies have clearly demonstrated the power of library synthesis and screening strategies, peptides and oligonucleotides generally have poor oral activities and rapid in vivo clearance;4 therefore their utility as bioavailable therapeutic agents is often limited. Due to the favorable pharmacokinetic properties of many small organic molecules (<600-700 molecular weight),5 the design, synthesis, and evaluation of libraries of these compounds6 has rapidly become a major frontier in organic chemistry. Lorin A. Thompson was born in Lexington, KY, in 1970. He received the Bachelor of Science degree from the University of North Carolina, Chapel Hill, in 1992 where he worked under the guidance of Joseph Desimone. He is currently pursuing his doctorate in the laboratory of Jonathan Ellman at UC Berkeley where he is the 1994 Glaxo-Wellcome fellow. His research interests include the development of synthetic methodology for organic library construction.

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Synthesis and Applications of Small Molecule Libraries.

http://alpha.chem.umb.edu/chemistry/ch611/documents/C-Htransitionmetalbonds.pdf

Carbonhydrogen-transition metal bonds

C-H oxidation has a long history and an ongoing presence in research at the forefront of chemistry and interrelated fields. As such, numerous highly useful articles and reviews have been written on this subject. Logically, these are generally written from the perspective of the scope and limitations of the reagents employed. This Minireview instead attempts to emphasize chemoselectivity imposed by the nature of the substrate. Consequently, many landmark discoveries in the field of C-H oxidation are not discussed, but hopefully the perspective taken herein will allow C-H oxidation reactions to be more readily incorporated into synthetic planning.

/pdf/if-c-h-bonds-could-talk-selective-c-h-bond-oxidation-3n1lbwrvjm.pdf

If C-H bonds could talk: selective C-H bond oxidation.

Owing to their high uptake capacity at low temperature and excellent reversibility kinetics, metal–organic frameworks have attracted considerable attention as potential solid-state hydrogen storage materials. In the last few years, researchers have also identified several strategies for increasing the affinity of these materials towards hydrogen, among which the binding of H2 to unsaturated metal centers is one of the most promising. Herein, we review the synthetic approaches employed thus far for producing frameworks with exposed metal sites, and summarize the hydrogen uptake capacities and binding energies in these materials. In addition, results from experiments that were used to probe independently the metal–hydrogen interaction in selected materials will be discussed.

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Hydrogen Storage in Microporous Metal-Organic Frameworks with Exposed Metal Sites

Structural studies on polynuclear osmium carbonyl hydrides. 16. Crystal structure of (.mu.-H)(.mu.-OMe)Os3(CO)10 and a comparison of the hinged Os(.mu.-H)2Os, Os(.mu.-H)(.mu.-OMe)Os, and Os(.mu.-OMe)2Os bridges in trinuclear (.mu.-H)n(.mu.-OMe)2-nOs3(CO)10 (n = 0-2) complexes

New metal-sulfur complexes from sulfur dioxide reduction by (.eta.5-C5R5)W(CO)3H (R = H, Me): structures of [CpW(CO)3]2(.mu.-S) and [Cp*W(CO)2(.mu.-S.cntdot.SO2)]2, a complex with strong SO2-sulfide bonding

Synthesis of cyclohexadiene complexes of (methylidyne)triruthenium clusters. The crystal structure of (.mu.-H)Ru3(.mu.3-COMe)(CO)8(1,3-C6H8) and a redetermination of the structure of (.mu.-H)Ru3(.mu.-COMe)(CO)10

Structural studies on tungsten methylidyne complexes. Molecular geometry of W(.tplbond.CH)(Cl)(PMe3)4 and W(.tplbond.CH.AlMe2-xCl1+x)(Cl)(PMe3)3 (x .simeq. 0.18), a Lewis acid adduct of the tungsten-methylidyne triple bond

When Fe(CO)/sub 5//KOH/MeOH solutions are treated with thallium salts, deep yellow-brown solutions result from which an anionic metal carbonyl complex can be isolated and is proposed to be (Et/sub 4/N)(Tl(Fe(CO)/sub 4/)/sub 2/)/sup 2 -/ ions (M = Zn, Cd, Hg). When methanol solutions of this complex stand at room temperature black crystals, 2, deposit slowly which will not redissolve in methanol. On the basis of analyses, spectroscopic data and x-ray analysis, 2 is shown to be (Et/sub 4/N)/sub 4/(Fe/sub 2/(CO)/sub 6/(..mu..-CO)(..mu..-Tl(Fe(CO)/sub 4/))/sub 2/)/sub 2/, an aggregate of 1 produced by loss of CO. Details of the structure of 2, which is structurally similar to Burlitch's recently reported Co/sub 2/(CO)/sub 6/(..mu..-CO)(..mu..-ZnCo(CO)/sub 4/)/sub 2/, will appear elsewhere. An x-ray diffraction study of crystals of a minor product showed it to be the highly unusual cluster compound 3 which can be viewed as a derivative of 2 in which the ..mu..-CO's are replaced by (..mu..-TlFe(CO)/sub 4/)/sup -/. The structure and bonding of this complex whose formula is (Et/sub 4/N)/sub 6/(Tl/sub 6/Fe/sub 10/(CO)/sub 36/) is the subject of this paper.

Harvey J. Wasserman

Papers

Structural studies on polynuclear osmium carbonyl hydrides. 16. Crystal structure of (.mu.-H)(.mu.-OMe)Os3(CO)10 and a comparison of the hinged Os(.mu.-H)2Os, Os(.mu.-H)(.mu.-OMe)Os, and Os(.mu.-OMe)2Os bridges in trinuclear (.mu.-H)n(.mu.-OMe)2-nOs3(CO)10 (n = 0-2) complexes

New metal-sulfur complexes from sulfur dioxide reduction by (.eta.5-C5R5)W(CO)3H (R = H, Me): structures of [CpW(CO)3]2(.mu.-S) and [Cp*W(CO)2(.mu.-S.cntdot.SO2)]2, a complex with strong SO2-sulfide bonding

Synthesis of cyclohexadiene complexes of (methylidyne)triruthenium clusters. The crystal structure of (.mu.-H)Ru3(.mu.3-COMe)(CO)8(1,3-C6H8) and a redetermination of the structure of (.mu.-H)Ru3(.mu.-COMe)(CO)10

Structural studies on tungsten methylidyne complexes. Molecular geometry of W(.tplbond.CH)(Cl)(PMe3)4 and W(.tplbond.CH.AlMe2-xCl1+x)(Cl)(PMe3)3 (x .simeq. 0.18), a Lewis acid adduct of the tungsten-methylidyne triple bond

An electron-deficient thallium Zintl-metal carbonylate: structure and bonding of [Et4N]6[Tl6Fe10(CO)36]