Homolytic reactivity of group 14 organometallic hydrides toward nitroxides
Homolytic reactivity of group 14 organometallic hydrides toward nitroxides
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DOI：
10.1021/jo972178i
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发表时间：
1998-03-06
影响因子：
3.6
通讯作者：
Chatgilialoglu, C
中科院分区：
文献类型：
--
作者：
Lucarini, M;Marchesi, E;Chatgilialoglu, C
本文研究了Et_3SiH、Ph_3GeH、Bu_3SnH和（Me_3Si）（3）SiH与2，2，6，6-四甲基-1-哌啶氧（克里思）及相关氮氧自由基的自发反应。以相对弱的金属-氢键为特征的金属络合物，如Ph 3GeH和Bu 3SnH，将克里思还原为相应的羟胺，而没有观察到与Et 3SiH和Ph 3SiH的反应。另一方面，三（三甲基甲硅烷基）硅烷能够在约20 ° C下将氮氧化合物还原为相应的羟胺和胺。1：1的比例。通过在热或光化学自由基引发剂的存在下重复上述反应，用（Me 3Si）（3）SiH和（Me 3Si）（2）Si（H）Ne以高产率获得克里思的脱氧，但用其它硅烷、锗烷和锡烷则不行。的克里思的减少由两个三甲基甲硅烷基取代的硅烷的机制提出，和动力学数据的各个步骤的整体反应的报告。特别是速率常数和活化参数已被测量的氢转移反应从几个硅烷受阻胺基自由基2，2，6，6-四甲基哌啶基。
The spontaneous reactions of Et3SiH, Ph3GeH, Bu3SnH, and (Me3Si)(3)SiH with 2,2,6,6-tetramethyl-1-piperidinoxyl (TEMPO) and related nitroxides have been investigated. Metal hydrides characterized by relatively weak metal-hydrogen bonds, like Ph3GeH and Bu3SnH, reduce TEMPO to the corresponding hydroxylamine while no reaction is observed with Et3SiH and Ph3SiH. Tris(trimethylsilyl)silane, on the other hand, is able to reduce the nitroxide to the corresponding hydroxylamine and amine in a ca. 1:1 ratio. By repeating the above reactions in the presence of thermal or photochemical radical initiators, deoxygenation of TEMPO was obtained in high yield with (Me3Si)(3)SiH and (Me3Si)(2)Si(H)Ne, but not with other silanes, germanes, and stannanes. A mechanism for the reduction of TEMPO by the two trimethylsilyl-substituted silanes is proposed, and kinetic data for the various steps of the overall reaction are reported. In particular rate constants and activation parameters have been measured for the hydrogen transfer reaction from several silanes to the hindered aminyl radical 2,2,6,6-tetramethylpiperidinyl.