title: Dioxo-molybdenum(VI) and mono-oxo-molybdenum(IV) complexes supported by new aliphatic dithiolene ligands: new models with weakened Mo=O bond characters for the arsenite oxidase active site.
abstract: The cis-dioxo-molybdenum(VI) complexes, [MoO2(L(H))2]2- (1b), [MoO2(L(S))(2)]2- (2b), and [MoO2(L(O))2]2- (3b) (L(H) = cyclohexene-1,2-dithiolate, L(S) = 2,3-dihydro-2H-thiopyran-4,5-dithiolate, and L(O) = 2,3-dihydro-2H-pyran-4,5-dithiolate), with new aliphatic dithiolene ligands were prepared and investigated by infrared (IR) and UV-vis spectroscopic and electrochemical methods. The mono-oxo-molybdenum(IV) complexes, [MoO(L(H))2]2- (1a), [MoO(L(S))2]2- (2a), and [MoO(L(O))2]2- (3a), were further characterized by X-ray crystal structural determinations. The IR and resonance Raman spectroscopic studies suggested that these cis-dioxo molybdenum(VI) complexes (1b-3b) had weaker Mo=O bonds than the common Mo(VI)O2 complexes. Complexes 1b-3b also exhibited strong absorption bands in the visible regions assigned as charge-transfer bands from the dithiolene ligands to the cis-MoO2 cores. Because the oxygen atoms of the cis-Mo(VI)O2 cores are relatively nucleophilic, these complexes were unstable in protic solvents and protonation might occur to produce Mo(VI)O(OH), as observed with the oxidized state of arsenite oxidase.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, 558-8585, Japan. sugimoto@sci.osaka-cu.ac.jp
authors.forename: Hideki
authors.initials: H
authors.lastname: Sugimoto
authors.forename: Makoto
authors.initials: M
authors.lastname: Harihara
authors.forename: Motoo
authors.initials: M
authors.lastname: Shiro
authors.forename: Kunihisa
authors.initials: K
authors.lastname: Sugimoto
authors.forename: Koji
authors.initials: K
authors.lastname: Tanaka
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Miyake
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tsukube
mesh_terms: D001665:Binding Sites; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D008982:Molybdenum / Q000737:chemistry* / Q000378:metabolism*; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism
chemical_list: D008024:Ligands; D008982:Molybdenum; D010088:Oxidoreductases; C078179:arsenite oxidase; D010100:Oxygen