A Model for the Active-Site Formation Process in DMSO Reductase Family Molybdenum Enzymes Involving Oxido−Alcoholato and Oxido−Thiolato Molybdenum(VI) Core Structures

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• 作者：Hideki Sugimoto ; Masanori Sato ; Kaori Asano ; Takeyuki Suzuki ; Kaoru Mieda ; Takashi Ogura ; Takashi Matsumoto ; Logan J. Giles ; Amrit Pokhrel ; Martin L. Kirk ; Shinobu Itoh
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：February 15, 2016
• 年：2016
• 卷：55
• 期：4
• 页码：1542-1550
• 全文大小：439K
• ISSN：1520-510X

文摘

New bis(ene-1,2-dithiolato)-oxido–alcoholato molybdenum(VI) and -oxido–thiolato molybdenum(VI) anionic complexes, denoted as [Mo^VIO(ER)L₂]^– (E = O, S; L = dimethoxycarboxylate-1,2-ethylenedithiolate), were obtained from the reaction of the corresponding dioxido-molybdenum(VI) precursor complex with either an alcohol or a thiol in the presence of an organic acid (e.g., 10-camphorsulfonic acid) at low temperature. The [Mo^VIO(ER)L₂]^– complexes were isolated and characterized, and the structure of [Mo^VIO(OEt)L₂]^– was determined by X-ray crystallography. The Mo(VI) center in [Mo^VIO(OEt)L₂]^– exhibits a distorted octahedral geometry with the two ene-1,2-dithiolate ligands being symmetry inequivalent. The computed structure of [Mo^VIO(SR)L₂]^– is essentially identical to that of [Mo^VIO(OR)L₂]^–. The electronic structures of the resulting molybdenum(VI) complexes were evaluated using electronic absorption spectroscopy and bonding calculations. The nature of the distorted O_h geometry in these [Mo^VIO(EEt)L₂]^– complexes results in a lowest unoccupied molecular orbital wave function that possesses strong π* interactions between the Mo(d_xy) orbital and the cis S(p_z) orbital localized on one sulfur donor from a single ene-1,2-dithiolate ligand. The presence of a covalent Mo–S_dithiolene bonding interaction in these monooxido Mo(VI) compounds contributes to their low-energy ligand-to-metal charge transfer transitions. A second important d–p π bonding interaction derives from the ∼180° O_oxo–Mo–E–C dihedral angle involving the alcoholate and thiolate donors, and this contributes to ancillary ligand contributions to the electronic structure of these species. The formation of [Mo^VIO(OEt)L₂]^– and [Mo^VIO(SEt)L₂]^– from the dioxidomolybdenum(VI) precursor may be regarded as a model for the active-site formation process that occurs in the dimethyl sulfoxide reductase family of pyranopterin molybdenum enzymes.