Högerl Manuel P, Serena Goh Li Min, Abou-Hamad Edy, Barman Samir, Dachwald Oliver, Pasha Farhan Ahmad, Pelletier Jeremie, Köhler Klaus, D'Elia Valerio, Cavallo Luigi, Basset Jean-Marie
KAUST Catalysis Center, King Abdullah University of Science and Technology 23955-6900 Thuwal Saudi-Arabia
Departments of Chemistry and Catalysis Research Center, Technical University of Munich Lichtenbergstrasse 4, Ernst-Otto-Fischer-Strasse 1 85747 Garching Germany.
RSC Adv. 2018 Jun 6;8(37):20801-20808. doi: 10.1039/c8ra02419g. eCollection 2018 Jun 5.
Vanadium oxytriisopropoxide (VO(O Pr)), 1, was grafted on highly dehydroxylated silica (SiO: aerosil silica treated at 700 °C under high vacuum) to generate compound 2 following the concepts and methodology of surface organometallic chemistry (SOMC). The resulting compound was analyzed by elemental analysis, FT-IR, H, C and V solid state (SS) NMR, Raman and EPR spectroscopies. The grafting reaction of 1 to generate 2 was found to lead to the formation of a monopodal surface complex [([triple bond, length as m-dash]Si-O-)V(O)(O Pr)], 2m, as well as bipodal [([triple bond, length as m-dash]Si-O-)V(O)(O Pr)], 2b, formed along with ([triple bond, length as m-dash]Si-O- Pr) moieties as an effect of the classical rearrangement of 2m with strained siloxane bridges. Upon controlled thermal treatment at 200 °C under high vacuum, 2m and 2b were found to mainly rearrange to tetrahedral VO moieties [([triple bond, length as m-dash]Si-O-)V(O)] (3) with formation of propylene whereas the ([triple bond, length as m-dash]Si-O- Pr) groups were preserved. The mechanism of the thermal rearrangement of the isopropoxide groups was investigated by a DFT approach revealing the occurrence of a concerted γ-H-transfer and olefin elimination mechanism.
按照表面有机金属化学（SOMC）的概念和方法，将三异丙氧基氧钒（VO(O Pr)）（1）接枝到高度脱羟基的二氧化硅（SiO：在高真空下于700°C处理的气相二氧化硅）上，生成化合物2。通过元素分析、傅里叶变换红外光谱（FT-IR）、氢、碳和钒的固态（SS）核磁共振、拉曼光谱和电子顺磁共振光谱对所得化合物进行了分析。发现1生成2的接枝反应导致形成单足表面配合物[([三键，长度为m破折号]Si-O-)V(O)(O Pr)]（2m），以及双足[([三键，长度为m破折号]Si-O-)V(O)(O Pr)]（2b），同时还形成了([三键，长度为m破折号]Si-O- Pr)部分，这是2m与应变硅氧烷桥发生经典重排的结果。在高真空下于200°C进行控制热处理时，发现2m和2b主要重排为四面体VO部分[([三键，长度为m破折号]Si-O-)V(O)]（3），同时生成丙烯，而([三键，长度为m破折号]Si-O- Pr)基团得以保留。通过密度泛函理论（DFT）方法研究了异丙氧基的热重排机理，揭示了协同γ-H转移和烯烃消除机理的存在。
