Kinetics and mechanism of the oxygen-transfer reaction between bis-(diethyldithiocarbamato)dioxomolybdenum(VI) and triphenylphosphine

Oxidomolybdenum(IV), ‐(V), ‐(VI) Complexes with Relevance to Molybdenum Enzymes: Oxygen Atom Transfer, Redox Chemistry and EPR Spectroscopy

“…The activation parameters [∆H ϶ ≈ 50 kJ mol -1 ; ∆S ϶ ≈ -(130-160) J mol -1 K -1 ] obtained are compatible with previously determined values for cis-dioxidomolybdenum(VI) complexes and are unexceptional (see Supporting Information). [12,[21][22][23] The bimolecular OAT from 1 involving the sterically demanding substrate PPh 3 proceeds slower, which is essentially ascribed to its larger activation entropy ∆S ϶ (-160 J mol -1 K -1 ). Similar trends were observed by employing cis-dioxidomolybdenum(VI) complexes with other ancillary N,O,S chelate ligands and phosphanes of varying steric demand.…”

“…Similar trends were observed by employing cis-dioxidomolybdenum(VI) complexes with other ancillary N,O,S chelate ligands and phosphanes of varying steric demand. [12,[21][22][23] The initially formed phosphorylmolybdenum(IV) complexes 2a-2d are unstable with respect to ligand loss. [16] This is especially pronounced for the larger phosphane oxides (2c, 2d; n = 1, 0).…”

A Catalytic Cycle Related to Molybdenum Enzymes Containing [MoVIO2]2+ Oxidized Active Sites

“…Reaction of Mo VI O 2 (cys−OR) 2 (cys−OR = cysteine ester), PPh 3 , and H 2 18 O resulted in the appearance of the label in the product OPPh 3 , but the mechanism of incorporation remains unclear . Several other model systems appear to require O 2 and/or H 2 O for regeneration of [Mo VI O 2 ] 2+ from [Mo IV O] 2+ centers. − …”

“…40 Several other model systems appear to require O 2 and/or H 2 O for regeneration of [Mo VI O 2 ] 2+ from [Mo IV O] 2+ centers. [41][42][43][44][45][46][47] Scheme 3…”

Symphoria: the success of modeling the active site function of oxo-molybdoenzymes

“…We have demonstrated that the model complex [Bu 4 N] 2 [Mo VI O 2 (mnt) 2 ] mimics the active site function of sulfite oxidase by undergoing an oxotransfer reaction with the physiological substrate HSO À 3 both in terms of saturation kinetics [12] as well as anionic inhibitions similar to that of native enzyme [13] even though it is not an accurate representation of the active structure of the enzyme [14] as required by criterion (i). The proposed mechanism which involves the substrate oxoanion binding to Mo VI leading to the formation of a hepta-coordinated Michaelis type complex [13], however, was questioned [15,16] and, instead, sulfur lone pair attack on one of the terminal oxogroups of [Mo VI O 2 (mnt) 2 ] 2À similar to that of the phosphorus lone pair attack in phosphine oxidation [17,18] has been suggested [15,16]. This has been substantiated by theoretical calculations, but, without taking into consideration the possibility of oxoanionic binding to Mo VI [19].…”