Lim B S, Willer M W, Miao M, Holm R H
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.
J Am Chem Soc. 2001 Aug 29;123(34):8343-9. doi: 10.1021/ja010786g.
The active sites of the xanthine oxidase and sulfite oxidase enzyme families contain one pterin-dithiolene cofactor ligand bound to a molybdenum atom. Consequently, monodithiolene molybdenum complexes have been sought by exploratory synthesis for structural and reactivity studies. Reaction of MoO(S(2)C(2)Me(2))(2) or MoO(bdt)(2) with PhSeCl results in removal of one dithiolate ligand and formation of MoOCl(2)(S(2)C(2)Me(2)) (1) or MoOCl(2)(bdt) (2), which undergoes ligand substitution reactions to form other monodithiolene complexes MoO(2-AdS)(2)(S(2)C(2)Me(2)) (3), MoO(SR)(2)(bdt) (R = 2-Ad (4), 2,4,6-Pr(i)(3)C(6)H(2) (5)), and MoOCl(SC(6)H(2)-2,4,6-Pr(i)(3))(bdt) (6) (Ad = 2-adamantyl, bdt = benzene-1,2-dithiolate). These complexes have square pyramidal structures with apical oxo ligands, exhibit rhombic EPR spectra, and 3-5 are electrochemically reducible to Mo(IV)O species. Complexes 1-6 constitute the first examples of five-coordinate monodithiolene Mo(V)O complexes; 6 approaches the proposed structure of the high-pH form of sulfite oxidase. Treatment of [MoO(2)(OSiPh(3))(2)] with Li(2)(bdt) in THF affords MoO(2)(OSiPh(3))(bdt) (8). Reaction of 8 with 2,4,6-Pr(i)(3)C(6)H(2)SH in acetonitrile gives MoO(2)(SC(6)H(2)-2,4,6-Pr(i)(3))(bdt) (9, 55%). Complexes 8 and 9 are square pyramidal with apical and basal oxo ligands. With one dithiolene and one thiolate ligand of a square pyramidal Mo(VI)O(2)S(3) coordination unit, 9 closely resembles the oxidized sites in sulfite oxidase and assimilatory nitrate reductase as deduced from crystallography (sulfite oxidase) and Mo EXAFS. The complex is the first structural analogue of the active sites in fully oxidized members of the sulfite oxidase family. This work provides a starting point for the development of both structural and reactivity analogues of members of this family.
黄嘌呤氧化酶和亚硫酸盐氧化酶家族的活性位点包含一个与钼原子结合的蝶呤 - 二硫烯辅因子配体。因此，人们通过探索性合成来寻找单二硫烯钼配合物，用于结构和反应性研究。MoO(S(2)C(2)Me(2))(2)或MoO(bdt)(2)与PhSeCl反应会导致一个二硫醇盐配体被去除，并形成MoOCl(2)(S(2)C(2)Me(2))（1）或MoOCl(2)(bdt)（2），它们会发生配体取代反应以形成其他单二硫烯配合物MoO(2-AdS)(2)(S(2)C(2)Me(2))（3）、MoO(SR)(2)(bdt)（R = 2-Ad（4），2,4,6-Pr(i)(3)C(6)H(2)（5））以及MoOCl(SC(6)H(2)-2,4,6-Pr(i)(3))(bdt)（6）（Ad = 2 - 金刚烷基，bdt = 苯 - 1,2 - 二硫醇盐）。这些配合物具有带有顶端氧配体的四方锥结构，呈现菱形EPR光谱，并且3 - 5在电化学上可还原为Mo(IV)O物种。配合物1 - 6构成了五配位单二硫烯Mo(V)O配合物的首个实例；6接近亚硫酸盐氧化酶高pH形式的推测结构。在四氢呋喃中用Li(2)(bdt)处理[MoO(2)(OSiPh(3))(2)]可得到MoO(2)(OSiPh(3))(bdt)（8）。8与2,4,6-Pr(i)(3)C(6)H(2)SH在乙腈中反应得到MoO(2)(SC(6)H(2)-2,4,6-Pr(i)(3))(bdt)（9，产率55%）。配合物8和9是带有顶端和基底氧配体的四方锥结构。作为四方锥Mo(VI)O(2)S(3)配位单元的一个二硫烯和一个硫醇盐配体，9与晶体学（亚硫酸盐氧化酶）和Mo EXAFS推导得出的亚硫酸盐氧化酶和同化硝酸盐还原酶的氧化位点极为相似。该配合物是亚硫酸盐氧化酶家族完全氧化成员活性位点的首个结构类似物。这项工作为开发该家族成员的结构和反应性类似物提供了一个起点。
