Carbon monoxide hydrogenation, deoxygenation, and carbon-carbon coupling promoted by [(silox)2TaH2]2
作者:Robert Toreki、Robert E. LaPointe、Peter T. Wolczanski
DOI:10.1021/ja00258a066
日期:1987.11
ads/ produces surface methylene groups, (3) C-C bond formation occurs through oligomerization of (CH/sub 2/)/sub ads/. Various organometallic species model the individual steps, yet fall short of corroborating the entire sequence. Reported herein is the carbonylation of ((silox)/sub 2/TaH/sub 2/)/sub 2/ (silox = t-Bu/sub 3/SiO/sup -/) and successive reactions which encompass the critical transformations
Fischer-Tropsch (FT) 反应被认为是未来能源问题的潜在解决方案,在过去的 15 年中引起了多相和均相催化研究人员的关注。将合成气 (CO/H/sub 2/) 转化为碳氢化合物和含氧化合物的最广泛接受的机制包括三个关键步骤:(1) CO 脱氧,大概是通过解离吸附;(2) H-转移到表面碳化物或 CO/sub ads/ 产生表面亚甲基,(3) CC 键的形成通过 (CH/sub 2/)/sub ads/ 的低聚反应发生。各种有机金属物种对各个步骤进行建模,但未能证实整个序列。
Ethylene and Alkyne Carbon−Carbon Bond Cleavage across Tungsten−Tungsten Multiple Bonds
作者:Rebecca L. M. Chamberlin、Devon C. Rosenfeld、Peter T. Wolczanski、Emil B. Lobkovsky
DOI:10.1021/om020037n
日期:2002.6.1
Treatment of [(silox)(2)WH](2) (1) with RCdropCR'(R = R'= H, CH3; R = H, R'= Ph) afforded thermally unstable [(silox)(2)W](2)(mu:eta(2),eta(2) -RCCR')(mu-H)(2) (R = R'= H, 2a; CH3,2b; R = H, R'= Ph, 2c), which lose H-2 and convert to [(silox)(2)W](2)(mu-CR)(mu-CR') (R = R'= H, 4a; CH3, 4b; R = H, R' = Ph, 4c). An X-ray structural study of 4b revealed a nearly square W2C2 core and a d(WW) of 2.720(2) Angstrom. Thermal degradation of 1(silox)(2)W(CH2CH3)](2) (5) also produced 4b, and with 2 equiv Of C2H4, its formation is nearly quantitative with 2 equiv of EtH as a byproduct. Na/Hg reduction of (silox)(2)C]WdropWCl(silox)(2) (3) in the presence of excess 2-butyne afforded [(silox)(2)W](2)(mu:eta(2),eta(2)-MeC2Me) (8), which could be treated with H2 to give 2b or thermolyzed to 4b. A similar reduction of 3 with excess ethylene present afforded 4a via [(silox)(2)W](2)(mu-CH)(mu-CH2)(H) (9, -78 degreesC) followed by H-2 loss; ethylene cleavage does not proceed via 2a or 8. Related cleavage chemistry was not observed for [(silox)(2)TaH2](2) (10) and excess ethylene, which formed (SilOX)2HTaEt]2 (11) and, ultimately, [(silox)(2)HTaEt](2) (mu-CHCH2)(mu-H)(2)[Ta(silox)(2)] (12) and EtH. An X-ray structural study of 12 confirmed its configuration. Spectroscopic features of the molecules are addressed, and plausible mechanisms of carbon-carbon bond cleavage-whose thermodynamic impetus is the formation of mu-CR bridges-are discussed.