BIOMIMICS OF VANADIUM BROMOPEROXIDASE - VANADIUM(V)-SCHIFF BASE-CATALYZED OXIDATION OF BROMIDE BY HYDROGEN-PEROXIDE
BIOMIMICS OF VANADIUM BROMOPEROXIDASE - VANADIUM(V)-SCHIFF BASE-CATALYZED OXIDATION OF BROMIDE BY HYDROGEN-PEROXIDE
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DOI：
10.1021/ic00074a017
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发表时间：
1993-10-27
影响因子：
4.6
通讯作者：
BUTLER, A
中科院分区：
文献类型：
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作者：
CLAGUE, MJ;KEDER, NL;BUTLER, A
六配位钒(V)配合物LVO(OEt)(EtOH) （H2L = N-（2-羟基苯基）水杨基二胺）是DMF溶液中过氧化氢氧化溴化物的催化剂前体。氧化的溴被有机底物捕获，通过产物分析，表明是一个双电子氧化的物种，而不是一个溴自由基。溴化反应对过氧化氢是定量的。建立了溴化反应化学计量的酸依赖关系。利用紫外/可见分光光度法、V-51核磁共振光谱和动力学数据，提出了反应机理：活性催化剂为LVO(OH)， LVO（OH）结合过氧化物释放h30 +，氧化溴化物并结合另一等量的过氧化物，生成LVO(O2)-。L*VO(OEt)(EtOH)，其中H2L*为N-（2-羧基苯基）水杨基二胺，也支持催化溴化反应。V-51核磁共振数据表明，L*2-在过氧化物络合作用下解离。用x射线晶体学测定了LVO(OEt)（EtOH）和L*VO(OEt)（EtOH）的结构。LVO(OEt)(EtOH)， VC17H2ONO5在正交体系Pbca空间群中结晶，a = 20.218(5)埃，b = 20.955(4)埃，c = 16.196(3)埃，Z = 16。细化后的R = 0.066， R(w) = 0.073。L*VO(OEt)(EtOH)， VC18H20NO6在正交体系空间群Fdd2中结晶，a = 17.7951(7)埃，b = 33.118(3)埃，c = 12.8834(5)埃，Z = 16。细化收敛到R = 0.040和R(w) = 0.048。
A six-coordinate vanadium(V) complex, LVO(OEt)(EtOH), where H2L = N-(2-hydroxyphenyl)salicylideneamine, is shown to be a catalyst precursor in the oxidation of bromide by hydrogen peroxide in DMF solution. The oxidized bromine species is trapped by organic substrates and, by product analysis, is shown to be a two-electron-oxidized species, rather than a bromine radical. The bromination reaction is quantitative with respect to hydrogen peroxide. The acid dependence of the stoichiometry of the bromination reaction is established. Using UV/vis spectrophotometry, V-51 NMR spectroscopy, and kinetic data, a mechanism is proposed: the active catalyst is LVO(OH), which, upon binding peroxide and releasing H3O+, oxidizes bromide and binds another equivalent of peroxide, generating the observed LVO(O2)-. L*VO(OEt)(EtOH), where H2L* is N-(2-carboxyphenyl)salicylideneamine, also supports catalytic bromination reactions. V-51 NMR data indicate that L*2- dissociates upon the complexation of peroxide. The structures of LVO(OEt)(EtOH) and L*VO(OEt)(EtOH) have been determined by X-ray crystallography. LVO(OEt)(EtOH), VC17H2ONO5, crystallizes in the orthorhombic system, space group Pbca, with a = 20.218(5) angstrom, b = 20.955(4) angstrom, c = 16.196(3) angstrom, and Z = 16. The refinement converged to R = 0.066 and R(w) = 0.073. L*VO(OEt)(EtOH), VC18H20NO6,crystallizes in the orthorhombic system, space group Fdd2, with a = 17.7951(7) angstrom, b = 33.118(3) angstrom, c = 12.8834(5) angstrom, and Z = 16. The refinement converged to R = 0.040 and R(w) = 0.048.