[Mo(Tm^Me)(O)₂Cl]:  An Alternative Functional Model of Sulfite Oxidase

Abstract

The hydrotris(methimazolyl)borate anion (TmMe) has been used to synthesize an alternative functional model ([Mo(TmMe)(O)2Cl]) of the metalloenzyme sulfite oxidase. It has been shown that the complex undergoes oxygen atom transfer chemistry and that it performs the primary function of the enzyme, sulfite oxidation. A method using ion chromatography has been developed to definitively prove that sulfite is oxidized to sulfate. Employment of a soft tripodal ligand has allowed us to tune the redox potentials of our complex so that they are significantly closer to those reported for sulfite oxidase.

Scorpionate Complexes as Models for Molybdenum Enzymes

“…Hydrotris(3‐methyl‐1‐imidazolyl‐2‐thione)borate (Tm Me , 22 ) complexes have also attracted attention as enzyme models especially as they exhibit a sulfur‐rich coordination sphere like Mo‐MPT enzyme active sites. Complexes of this type were simultaneously reported by the groups of Reglinski and Carrano . Both groups reported the synthesis, crystal structure and OAT reactivity of [Tm Me MoO 2 Cl].…”

“…The dioxido complex is also capable of catalyzing the oxidation of PPh 3 to OPPh 3 using Me 2 SO as oxidant, emulating the reactions catalyzed by DMSOR . Significantly, Reglinski and co‐workers reported that [Tm Me MoO 2 Cl] mimics SO activity by oxidizing sulfite to sulfate, a rarely reported reaction in Mo enzyme model chemistry.…”

Synthesis, electrochemistry, geometric and electronic structure of oxo-molybdenum compounds involved in an oxygen atom transferring system

“…Studies from several laboratories have demonstrated that a variety of discrete oxo-molybdenum(VI) complexes can carry out the atom transfer chemistry when reacted with oxygen atom abstractors producing oxidized species such as tertiary phosphines oxides, sulfoxides, N-oxides, tertiary arsine-oxide, or sulfate [6][7][8][9][10][11][12][13][14][15][16][17]. Using tertiary phosphines (PR 3 ), we have demonstrated that OAT reactions from [Mo VI O 2 ] 2+ cores proceed in steps involving the formation of a phosphoryl coordinated Mo(IV) center which losses the phosphoryl ligand, and the vacant site is occupied by a solvent molecule [18][19][20][21].…”

Synthetic Bioinorganic Chemistry: Scorpionates Turn 50

“…For example, the first structurally characterized zinc hydroxide complex supported by a tridentate sulfur ligand, (Tm Ph )ZnOH, was prepared as a structural model for the zinc-containing enzyme 5-aminolevulinate dehydratase (ALAD) [124]. A couple of Tm Me complexes of molybdenum stoichiometrically convert sulfite to sulfate and thereby serve as functional models for sulfite oxidase [125,126]. The unusual trigonal pyramidal cation [(Tm Ph )Pb] + ( Fig.…”