000204441 001__ 204441
000204441 005__ 20190527110905.0
000204441 0247_ $$2doi$$a10.1021/ja020136s
000204441 022__ $$a0002-7863
000204441 02470 $$2ISI$$a000180311800041
000204441 037__ $$aARTICLE
000204441 245__ $$aPerhydrocarbyl Re-VII complexes: Comparison of molecular and surface complexes
000204441 260__ $$bAMER CHEMICAL SOC$$c2003
000204441 269__ $$a2003
000204441 336__ $$aJournal Articles
000204441 520__ $$aThe molecular complex [Re(equivalent toC(t)Bu)(=(CHBu)-Bu-t)((CH2Bu)-Bu-t)2] (1) reacts with a silica partially dehydroxylated at 700 degreesC to give syn-2, [(equivalent toSiO)Re(equivalent toC(t)Bu)(=(CHBu)-Bu-t)((CH2Bu)-Bu-t)], as a single isomer according to mass-balance analysis, IR, and solid-state NMR spectroscopy. 1 D and 2D solid-state NMR.(HETCOR and long-range HETCOR) on a C-13-labeled-2 has allowed us to observe the chemical shifts of all carbons (including those that are not labeled) and ascertain their assignments. Moreover, EXAFS data are consistent with the presence of two carbons at a relatively short distance (1.79 Angstrom), which cannot be cleconvoluted, but which are consistent with the presence of alkylidene and alkylidyne carbons along with two other first neighbors at a longer distance (2.01 Angstrom), the alkyl carbon and the 0 atom by which the Re is attached to the surface. Moreover, the data also suggest the presence of a siloxane bridge of the silica surface at 2.4 Angstrom in the coordination sphere of the Re center. Thermal and photochemical treatment allow us to observe the anti isomer, which was also fully characterized by 1D and 2D solid-state NMR. This behavior parallels the reactivity of molecular Re complexes, and their respective H-1 and C-13 chemical shifts match those of the corresponding molecular analogues syn- and anti-2m and n. Finally, the grafting of 1 onto silica involves the reaction of both the alkyl and the alkylidene ligand with an equiprobability, leaving the alkylidyne as a spectator ligand. Noteworthy is the formation of 2 [(equivalent toSiO)Re(equivalent toC(t)Bu)(=(CHBu)-Bu-t)((CH2Bu)-Bu-t)], rather than the corresponding trisneopentyl-neopentylidyne Re complex, monografted on silica, [(equivalent toSiO)Re(equivalent toC(t)Bu)((CH2Bu)-Bu-t)(3)], which would have been expected from the reactivity of I with various molecular Bronsted acids and which also suggests that a proximal siloxane bridge forces the alpha-H abstraction process, leading to syn-2a.
000204441 700__ $$aChabanas, M
000204441 700__ $$aBaudouin, A
000204441 700__ $$aCoperet, C
000204441 700__ $$aBasset, JM
000204441 700__ $$aLukens, W
000204441 700__ $$aLesage, A
000204441 700__ $$aHediger, S
000204441 700__ $$g251248$$aEmsley, L$$0248253
000204441 773__ $$j125$$tJournal of the American Chemical Society$$k2$$q492-504
000204441 909C0 $$xU12975$$0252518$$pLRM
000204441 909CO $$pSB$$particle$$ooai:infoscience.tind.io:204441
000204441 937__ $$aEPFL-ARTICLE-204441
000204441 970__ $$aISI:000180311800041/LRM
000204441 973__ $$rREVIEWED$$sPUBLISHED$$aOTHER
000204441 980__ $$aARTICLE