Stoichiometric and Catalytic Activation of the - and 
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- 作者：David Brevet ; Yves Mugnier ; Fré ; dé ; ric Lemaî ; tre ; Dominique Lucas ; Soth Samreth ; and Pierre D. Harvey
- 刊名：Inorganic Chemistry
- 出版年：2003
- 出版时间：August 11, 2003
- 年：2003
- 卷：42
- 期：16
- 页码：4909 - 4917
- 全文大小：223K
- 年卷期：v.42,no.16(August 11, 2003)
- ISSN：1520-510X
文摘
The title cluster (Pd32+) exhibits a pronounced affinity for Br- ions to form the very stable Pd3(Br)+ adduct. Upona 2-electron reduction, a dissociative process occurs generating Pd30 and eliminating Br- according to an ECEmechanism (electrochemical, chemical, electrochemical). At a lower temperature (i.e. -20 
C), both ECE and EECprocesses operate. This cluster also activates the C-Br bond, and this work deals with the reactivity of Pd32+ with2,3,4-tri-O-acetyl-5-thioxylopyranosyl bromide (Xyl-Br), both 
- and 
-isomers. The observed inorganic product isPd3(Br)+ again, and it is formed according to an associative mechanism involving Pd32+···Xyl-Br host-guestassemblies. In an attempt to render the C-Br bond activation catalytic, these species are investigated under reductionconditions at two potentials (-0.9 and -1.25 V vs SCE). In the former case, the major product is Xyl-H, issuedfrom a radical intermediate Xyl
abstracting an H atom from the solvent. Evidence for Xyl is provided by thetrapping with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) and DMPO (5,5'-dimethylpyrroline-N-oxyde). In the secondcase, only one product is observed, 3,4-di-O-acetyl-5-thioxylal, which is issued from the Xyl- intermediate anion.
C), both ECE and EECprocesses operate. This cluster also activates the C-Br bond, and this work deals with the reactivity of Pd32+ with2,3,4-tri-O-acetyl-5-thioxylopyranosyl bromide (Xyl-Br), both - and -isomers. The observed inorganic product isPd3(Br)+ again, and it is formed according to an associative mechanism involving Pd32+···Xyl-Br host-guestassemblies. In an attempt to render the C-Br bond activation catalytic, these species are investigated under reductionconditions at two potentials (-0.9 and -1.25 V vs SCE). In the former case, the major product is Xyl-H, issuedfrom a radical intermediate Xyl abstracting an H atom from the solvent. Evidence for Xyl is provided by thetrapping with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) and DMPO (5,5'-dimethylpyrroline-N-oxyde). In the secondcase, only one product is observed, 3,4-di-O-acetyl-5-thioxylal, which is issued from the Xyl- intermediate anion.