Structural and functional models in molybdenum and tungsten bioinorganic chemistry: description of selected model complexes, present scenario and possible future scopes

Abstract

A brief description about some selected model complexes in molybdenum and tungsten bioinorganic chemistry is provided. The synthetic strategies involved and their limitations are discussed. Current status of molybdenum and tungsten bioinorganic modeling chemistry is presented briefly and synthetic problems associated therein are analyzed. Possible future directions which may expand the scope of modeling chemistry are suggested.

Bioinspired functional analogs of the active site of molybdenum enzymes: Intermediates and mechanisms

“…Formation of -oxido complexes seems to be suppressed employing anionic bis(dithiolene) complexes (Scheme 4c) [42,43,46] probably due to electrostatic repulsion which represents an "electronic solution" to the dinucleation problem [59]. Forward .…”

“…The second task requires the positioning of redox cofactors with redox potential gradients in a well-defined distance and orientation. At the current stage of synthetic bioinspired chemistry this is probably a quite ambitious goal, but attempts in these directions are actively pursued in several groups around the world [24,[41][42][43][44][45][46][47].…”

Dioxidomolybdenum(VI) Complexes of Tripodal Tetradentate Ligands for Catalytic Oxygen Atom Transfer between Benzoin and Dimethyl Sulfoxide and for Oxidation of Pyrogallol

“…It is also an important cofactor for many enzymes, of which at least fifty have been isolated and characterized biochemically , . Excluding nitrogenases, which contain the multinuclear iron–molybdenum cofactor (FeMoco) as the active site, most other molybdenum‐containing oxotransferases are mononuclear and fall into three broad categories depending on their active‐site structure, that is, sulfite oxidases, dimethyl sulfoxide reductases, and xanthine oxidases . The enzymes containing the molybdenum cofactor (Moco) may be hydroxylases or oxotransferases and catalyze reactions involving the transfer of oxygen to and from the substrate in a two‐electron process.…”

“…Dimethyl sulfoxide reductases reduce dimethyl sulfoxide (DMSO) to dimethyl sulfide (DMS) along with oxido transfer and the consequent oxidation of Mo IV to Mo VI possibly via a Mo V intermediate . The active‐site structure of a fully oxidized Mo VI DMSO reductase comprises a Mo VI centre coordinated to two pyranopterin cofactors in an L 2 Mo VI Y(X) trigonal‐prismatic coordination geometry, in which Y is the labile Mo=O group and X is a serinate ligand that completes the metal coordination sphere of the oxidized enzyme . Several synthetic models based on the cis ‐[MoO 2 ] 2+ core have been proposed and evaluated for their oxygen atom transfer properties and related mechanistic pathways.…”

“…[1,2] Excluding nitrogenases, which contain the multinuclear iron-molybdenum cofactor (FeMoco) as the active site, most other molybdenum-containing oxotransferases are mononuclear and fall into three broad categories depending on their active-site structure, that is, sulfite oxidases, dimethyl sulfoxide reductases, and xanthine oxidases. [3][4][5][6][7] The enzymes containing the molybdenum cofactor (Moco) may be hydroxylases or oxotransferases and catalyze reactions involving the transfer of oxygen to and from the substrate in a twoelectron process. Mononuclear molybdenum-based enzymes are crucial to carbon, nitrogen, and sulfur biogeochemical cycles and serve primarily to transfer oxygen atoms to physiological substrates.…”