Synthetic Analogues and Reaction Systems Relevant to the Molybdenum and Tungsten Oxotransferases

The biologically relevant oxygen atom transfer chemistry of molybdenum: from synthetic analogue systems to enzymes

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.

Bioinorganic chemistry of pterin-containing molybdenum and tungsten enzymes

The ligand 2-mercapto-3,5-di-tert-butylaniline, H[LAP], an o-aminothiophenol, reacts with metal(II) salts of Ni and Pd in CH3CN or C2H5OH in the presence of NEt3 under strictly anaerobic conditions with formation of beige to yellow cis-[MII(LAP)2] (M = Ni (1), Pd (2)) where (LAP)1- represents the o-aminothiophenolate(1-) form. The crystal structure of cis-[PdII(LAP)2][HN(C2H5)3][CH3CO2] has been determined by X-ray crystallography. In the presence of air the same reaction produces dark blue solutions from which mixtures of the neutral complexes trans/cis-[MII(LISQ)2] (M = Ni (1a/1b), Pd (2a/2b), and Pt (3a/3b)) have been isolated as dark blue−black solid materials. By using HPLC the mixture of 3a/3b has been separated into pure samples of 3a and 3b, respectively; (LISQ)1- represents the o-iminothionebenzosemiquinonate(1-) π-radical. The structures of 1a·dmf and 3a·CH2Cl2 have also been determined. All compounds are square-planar and diamagnetic. 1H NMR spectroscopy established the cis ⇋ trans equilibrium ...

Experimental Evidence for the Noninnocence of o-Aminothiophenolates: Coordination Chemistry of o-Iminothionebenzosemiquinonate(1-) π-Radicals with Ni(II), Pd(II), Pt(II)

Synthesis, spectral and X-ray structural characterization of [cis-MoO2(L)(solv)] (L=salicylidene salicyloyl hydrazine) and its use as catalytic oxidant

A series of dioxo-Mo(VI) Schiff base complexes of the type MoO 2 (R-L)(solv) has been prepared: L=2-(salicylideneamino)-phenolate(2-) (sap) or 2-(salicylideneamino)benzenethiolato(2-) (ssp); solv=solvent. Salicylidene ring substituents R were selected to promote solubility and crystallinity. The unsubstituted complexes MoO 2 (sap)(solv) and MoO 2 (ssp)(solv) have been previously reported. The structures of two members of the series were determined

Oxomolybdenum(IV,V,VI) Complexes: Structures, Reactivities, and Criteria of Detection of Binuclear (μ-oxo)molybdenum(V) Products in Oxygen Atom Transfer Systems

Oxomolybdenum(IV,V,VI) Complexes: Structures, Reactivities, and Criteria of Detection of Binuclear (μ-Oxo)molybdenum(V) Products in Oxygen Atom Transfer Systems.

Julia A. Craig

Papers

Oxomolybdenum(IV,V,VI) Complexes: Structures, Reactivities, and Criteria of Detection of Binuclear (μ-oxo)molybdenum(V) Products in Oxygen Atom Transfer Systems

Oxomolybdenum(IV,V,VI) Complexes: Structures, Reactivities, and Criteria of Detection of Binuclear (μ-Oxo)molybdenum(V) Products in Oxygen Atom Transfer Systems.