scispace - formally typeset
Search or ask a question
Author

Edward I. Stiefel

Other affiliations: Kettering University
Bio: Edward I. Stiefel is an academic researcher from ExxonMobil. The author has contributed to research in topics: Molybdenum & Catalysis. The author has an hindex of 45, co-authored 170 publications receiving 5406 citations. Previous affiliations of Edward I. Stiefel include Kettering University.


Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, the tetreaalkylthiuram disulfides were added to WSe42 to obtain the new complexes WvSe2(R2NCS2)3, revealing the induced internal electron transfer similar to that of MoS42- but different from the reactivity of WS42- as predicted by comparison of the lowest energy charge transfer transitions of the reactants.
Abstract: Addition of tetreaalkylthiuram disulfides R2NC(S)S–SC(S)NR2(R = Et and Bui) to WSe42– yields the new complexes WvSe2(R2NCS2)3, revealing that WSe42– undergoes induced internal electron transfer similar to that of MoS42–, but different from the reactivity of WS42–, as predicted by comparison of the lowest energy charge transfer transitions of the reactants.

7 citations

Patent
25 Apr 1984
TL;DR: In this paper, a non-aqueous formulation of the formula for Cat n 3/n [Co(MoS 4 ) 2 ] was proposed, where Cat is a mono, di or trivalent cation and n is 1, 2 or 3, respectively.
Abstract: Compositions of the formula [(Cat n )] 3/n [Co(MoS 4 ) 2 ] wherein Cat is a mono, di or trivalent cation and n is 1, 2 or 3, respectively, have been prepared in non-aqueous media. The [Co(MoS 4 ) 2 ] 3 - anion has the general structure Cat is preferably an alkyl substituted quaternary ammonium compound.

7 citations

Book ChapterDOI
01 Jan 1980
TL;DR: Nitrogenase is a complex of two separately purifiable proteins that catalyzing the reduction of N2 to ammonia has ATP-hydrolyzing activity, ATP-dependent H2-evolution activity, and supports a reaction between D2 and protons (from H2O) to form HD.
Abstract: Nitrogenase is a complex of two separately purifiable proteins, the molybdenum-iron protein [MoFe] and the iron protein [Fe].1,2 In addition to catalyzing the reduction of N2 to ammonia, nitro genase has ATP-hydrolyzing activity,3 ATP-dependent H2-evolution activity,4 and supports a reaction between D2 and protons (from H2O) to form HD.5 In the absence of other substrates, all the reductant consumed is used to reduce protons to H2. When N2 is added as a substrate, an apparent maximum of 75% of the electrons reduce N2 while the remainder still reduce protons.6

7 citations

Patent
25 Oct 1990
TL;DR: In this article, a method for preparing molybdenum and sulfur containing compounds of the general formula X 2 Mo 2 S 12.yH 2 O, where X is a cation selected from the group consisting of Na +, K +, R 4 N +, R 3 NH+, R 2 NH 2 +,RNH 3 +, NH 4 +, RCN 2 N, R 4 P +, RCN 4 As +,(R 3 P) 2 N + ), R is a C 1 -C 30 alkyl, C 6 -
Abstract: A method for preparing molybdenum and sulfur containing compounds of the general formula X 2 Mo 2 S 12 .yH 2 O, where X is a cation selected from the group consisting of Na + , K + , R 4 N + , R 3 NH + , R 2 NH 2 + , RNH 3 + , NH 4 + , R 4 P + , R 4 As + ,(R 3 P) 2 N + , R is a C 1 -C 30 alkyl, C 6 -C 30 aryl, C 7 -C 30 aralkyl or C 2 -C 30 alkoxyalkyl group and mixtures thereof, and y is from 0 to 2. The method comprises preparing a sulfide solution that contains from about 9 wt. % to about 13 wt. % sulfide sulfur; contacting the solution with elemental sulfur and a hydroxide; adding a molybdenum compound for a time and at a temperature sufficient to form a reaction mixture and a precipitate; separating the precipitate; and contacting the remaining reaction mixture with additional sulfide solution to form (NH 4 ) 2 Mo 2 S 12 .yH 2 O. When compounds containing cations other than NH 4 + are to be produced, the (NH 4 ) 2 Mo 2 S 12 .yH 2 O is contacted with a cation exchange compound containing a desired substitute cation selected from above and an anion selected from the group consisting of Cl - , Br - , F - , I - , BF 4 - , PF 6 - , OH - , BR 4 - where R is a C 1 -C 30 alkyl, C 6 -C 30 aryl, C 7 -C 30 aralkyl or C 2 -C 30 alkoxyalkyl group, and mixtures thereof, in the presence of a solvent and for a time and at a temperature sufficient to form X 2 Mo 2 S 12 .yH 2 O, where X is other than NH 4 + .

7 citations

Patent
23 Nov 1992
TL;DR: In this article, the authors proposed new compositions of matter having the formula AnCx, wherein A is a monovalent cation and Cx is a fullerene anion, preferably wherein x is equal to 60 and 70.
Abstract: The present invention relates to new compositions of matter having the formula AnCx, wherein A is a monovalent cation and Cx is a fullerene anion, preferably wherein x is equal to 60 and 70. The present invention also relates to a process for preparing the composition by applying an electrical potential to a non-aqueous solution of a fullerene and a salt containing a monovalent cation. The present invention also relates to a method for electrochemically generating fulleride salts as a solution in other hydrocarbons. The present invention also relates to a method for electrochemically preparing solid fulleride salts. The compositions may be used as electrode material in reversible electrochemical cells, superconductors, spin labels, magnetic thermometers, organic, and polymer precursors.

6 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: A great deal of research effort is now concentrated on two aspects of ferritin: its functional mechanisms and its regulation and the apparent links between iron and citrate metabolism through a single molecule with dual function are described.

2,486 citations

Journal ArticleDOI
TL;DR: The geometries of 131 SBUs, their connectivity and composition of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) towards construction and synthesis of metal-organic frameworks (MOFs).
Abstract: This critical review presents a comprehensive study of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) towards construction and synthesis of metal–organic frameworks (MOFs). We describe the geometries of 131 SBUs, their connectivity and composition. This contribution presents a comprehensive list of the wide variety of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) in the construction and synthesis of metal–organic frameworks. The SBUs discussed here were obtained from a search of molecules and extended structures archived in the Cambridge Structure Database (CSD, version 5.28, January 2007) which included only crystals containing metal carboxylate linkages (241 references).

2,145 citations

Journal ArticleDOI
TL;DR: It is now well-established that all molybdenum-containing enzymes other than nitrogenase fall into three large and mutually exclusive families, as exemplified by the enzymes xanthine oxidation, sulfite oxidase, and DMSO reductase; these enzymes represent the focus of the present account.
Abstract: Molybdenum is the only second-row transition metal required by most living organisms, and is nearly universally distributed in biology. Enzymes containing molybdenum in their active sites have long been recognized,1 and at present over 50 molybdenum-containing enzymes have been purified and biochemically characterized; a great many more gene products have been annotated as putative molybdenum-containing proteins on the basis of genomic and bioinformatic analysis.2 In certain cases, our understanding of the relationship between enzyme structure and function is such that we can speak with confidence as to the detailed nature of the reaction mechanism and, with the availability of high-resolution X-ray crystal structures, the specific means by which transition states are stabilized and reaction rate is accelerated within the friendly confines of the active site. At the same time, our understanding of the biosynthesis of the organic cofactor that accompanies molybdenum (variously called molybdopterin or pyranopterin), the manner in which molybdenum is incorporated into it, and then further modified as necessary prior to insertion into apoprotein has also (in at least some cases) become increasingly well understood. It is now well-established that all molybdenum-containing enzymes other than nitrogenase (in which molybdenum is incorporated into a [MoFe7S9] cluster of the active site) fall into three large and mutually exclusive families, as exemplified by the enzymes xanthine oxidase, sulfite oxidase, and DMSO reductase; these enzymes represent the focus of the present account.3 The structures of the three canonical molybdenum centers in their oxidized Mo(VI) states are shown in Figure 1, along with that for the pyranopterin cofactor. The active sites of members of the xanthine oxidase family have an LMoVIOS-(OH) structure with a square-pyramidal coordination geometry. The apical ligand is a Mo=O ligand, and the equatorial plane has two sulfurs from the enedithiolate side chain of the pyranopterin cofactor, a catalytically labile Mo–OH group, and most frequently a Mo=S. Nonfunctional forms of these enzymes exist in which the equatorial Mo=S is replaced with a second Mo=O; in at least one member of the family the Mo=S is replaced by a Mo=Se, and in others it is replaced by a more complex –S–Cu–S–Cys to give a binuclear center. Members of the sulfite oxidase family have a related LMoVIO2(S–Cys) active site, again square-pyramidal with an apical Mo=O and a bidentate enedithiolate Ligand (L) in the equatorial plane but with a second equatorial Mo=O (rather than Mo–OH) and a cysteine ligand contributed by the protein (rather than a Mo=S) completing the molybdenum coordination sphere. The final family is the most diverse structurally, although all members possess two (rather than just one) equiv of the pyranopterin cofactor and have an L2MoVIY(X) trigonal prismatic coordination geometry. DMSO reductase itself has a catalytically labile Mo=O as Y and a serinate ligand as X completing the metal coordination sphere of oxidized enzyme. Other family members have cysteine (the bacterial Nap periplasmic nitrate reductases), selenocysteine (formate dehydrogenase H), –OH (arsenite oxidase), or aspartate (the NarGHI dissimilatory nitrate reductases) in place of the serine. Some enzymes have S or even Se in place of the Mo=O group. Members of the DMSO reductase family exhibit a general structural homology to members of the aldehyde:ferredoxin oxidoreductase family of tungsten-containing enzymes;4 indeed, the first pyranopterin-containing enzyme to be crystallographically characterized was the tungsten-containing aldehyde:ferredoxin oxidoreductase from Pyrococcus furiosus,5 a fact accounting for why many workers in the field prefer “pyranopterin” (or, perhaps waggishly, “tungstopterin”) to “molybdopterin”. The term pyranopterin will generally be used in the present account. Open in a separate window Figure 1 Active site structures for the three families of mononuclear molybdenum enzymes. The structures shown are, from left to right, for xanthine oxidase, sulfite oxidase, and DMSO reductase. The structure of the pyranopterin cofactor common to all of these enzymes (as well as the tungsten-containing enzymes) is given at the bottom.

1,541 citations