Grace J. J. Chen

Bio: Grace J. J. Chen is an academic researcher from Kettering University. The author has contributed to research in topics: Acetylene & Electron donor. The author has an hindex of 9, co-authored 15 publications receiving 600 citations.

Synthesis of molybdenum(IV) and molybdenum(V) complexes using oxo abstraction by phosphines. Mechanistic implications

Abstract: Die Reaktionen der Mo(VI)-Verbindungen (I) mit tert. Phosphinen demonstrieren einen bequemen Weg zur Darstellung von Mo(V)-Spezies wie (IIa) und (IIb) und von Mo(IV)-Komplexen wie (IIIb) und (IIIc).

Binding and activation of enzymic substrates by metal complexes. 4. Structural evidence for acetylene as a four-electron donor in carbonylacetylenebis(diethyldithiocarbamate)tungsten

Abstract: Eine CH, Cl2-Losung von Bis1[N,N-diethyldithiocarbamato]-dicarbonyl-triphenylphosphinwolfram reagiert in reiner Acetylenatmosphare zu der diamagnetischen Titelverbindung (I), die durch IR-, NMR- und sichtbares Elektronenspektrum charakterisiert wurde.

Synthetic utility of molybdenum-diazene adducts: preparation, reactions, and spectral properties of oxo-free and (18O)oxo molybdenum complexes

Abstract: Preparation des complexes de type Mo(LL) 2 (DEAZ) x (LL=S 2 CNR) 2 , S 2 P(i-Pr) 2 , S 2 P(OEt) 2 (DEAZ=diazenedicarboxylate de diethyle). On prepare egalement Mo 18 O 2 (LL) 2 , Mo 18 O(LL) 2 , Mo 2 18 O 3 (LL) 4 , Mo 2 18 O 4 (LL) 2 et Mo 2 18 O 3 S(LL) 2

Four-electron alkyne ligands in molybdenum(II) and tungsten(II) complexes

Abstract: Publisher Summary This chapter explores that the term “four-electron donor,” which is used to describe the alkyne ligand in circumstances where alkyne π ⊥ donation supplements classic metal–olefin bonding. The utility of this scheme lies in its simplicity, and with some reluctance is relied on the “four-electron donor” terminology to suggest global properties of metal alkyne monomers. The general implications and specific hazards characterizing these descriptors are typical of broad classification schemes in chemistry—they are often conceptually helpful but seldom specifically correct. Criteria for recognizing four-electron alkyne donation encompass stoichiometry, structure, spectra, and reactivity. The chapter reviews that the chemistry that has been developed for molybdenum (II) and tungsten (II) alkyne monomers encompasses syntheses, structures, spectra, molecular orbital descriptions, and reactions. The Mo (II) and W (II) complexes addressed in the chapter are not unique in terms of alkyne π ⊥ donation. Related alkyne chemistry is appearing for d4 metals other than molybdenum and tungsten, as well as for d 2 complexes in general. The chapter also examines that chromium alkyne chemistry and reflects the importance of π ⊥ donation, but the stoichiometries differ from those of heavier Group VI monomers.

Bioinorganic chemistry of pterin-containing molybdenum and tungsten enzymes

Abstract: Publisher Summary This chapter presents a discussion on the bioinorganic chemistry of pterin-containing molybdenum and tungsten enzymes. The chapter focuses on the current results and the interplay of model and enzyme chemistry. Attention is directed to sulfite oxidase and xanthine oxidase, the archetypal examples of molybdenum enzymes, containing, respectively, dioxo-Mo(VI) and oxo-thio-Mo(VI) oxidized centers. Biochemical and model studies of molybdopterin, Mo-co, and related species are described in this chapter. A brief survey on the physical and spectroscopic techniques employed in the study of the enzymes is presented and their impact on the current understanding of the coordination about the molybdenum atom in sulfite oxidase and xanthine oxidase is discussed. Structural and spectroscopic models are also presented in the chapter. The chapter also explains the xanthine oxidase cycle and facets of intramolecular electron transfer in molybdenum enzymes. The pterin-containing tungsten enzymes and the evolving model chemistry are discussed. Current descriptions of the coordination environment of the molybdenum centers of the enzymes rest primarily upon the comparisons of the spectra of the enzymes with the spectra of well-characterized molybdenum complexes. The unexpected discovery that several hyperthermophilic organisms possess pterin-containing tungsten enzymes promises to stimulate the development of oxo-thio-tungsten chemistry.

Organometallic Compounds Containing Oxygen Atoms

Abstract: Publisher Summary This chapter discusses the organometallic compounds containing oxygen atoms. At present, the range of organic ligands found in organometallic oxo compounds is quite restricted, the majority being either η-C 5 R 5 or alkyls or aryls having no β-hydrogen atom. Two basic routes to organometallic oxo compounds may be envisaged addition of an organic ligand to an inorganic oxo complex or addition of oxygen to an organometallic compound. Exhaustive decarbonylation with concomitant oxidation of a cyclopentadienyl metal carbonyl has proved to be a useful preparative route to cyclopentadienyl metal oxo compounds having no other ligands. In the ethylene complex, the oxo and ethylene ligands are cis to one another and the C–C axis of the ethylene is perpendicular to the M–O bond, a configuration that maximizes π bonding between the W(IV) (d 2 ) and the ethylene. Complexes containing cyclopentadienyl and oxygen as coligands are of two basic types: those containing a terminal double bond between a metal and oxygen, [M=O], and those containing one or more doubly bridging oxygen atoms, [M(μ 2 -O) n M]. The clusters are held together by M–O bonds and the M–( η 5 -C 5 H 5 ) bonding is of the usual type. Parallel to the development of organometallic clusters containing oxygen atoms has been the preparation of organometallic polyoxometallates. Although the organometallic groups are on the surface of the polyoxometallate, they are strongly and covalently bonded to the peripheral oxygen atoms.