Metathetical reactions of rhenium(VII) alkylidene-alkylidyne complexes of the type Re(CR')(CHR')[OCMe(CF3)2]2 (R' = CMe3 or CMe2Ph) with terminal and internal olefins

Olefin Metathesis by Well-Characterized Re(VII) Alkylidene/Alkylidyne Complexes

“…[Re(C-t-Bu)(CH-t-Bu)(Ar'NH2)CI2h (1.89 (1) A) 10 and Re(C-t-Bu)(CH-t-Bu)(pyhI2 (1.873 (9) ;\),13 while the Re-C(2)-C(15) angle of 151 (1)° is more comparable to that in…”

Strategies to Immobilize Well‐Defined Olefin Metathesis Catalysts: Supported Homogeneous Catalysis vs. Surface Organometallic Chemistry

“…[87] In contrast, the welldefined silica supported Re alkylidene complex 17s has shown unprecedented activities in olefin metathesis (Scheme 16b), [88][89][90][91][92] which exceeds those obtained for both heterogeneous and homogeneous Re-based catalysts (18). [93,94] Beside being characterized at a molecular level as the syn-isomer by a combination of spectroscopic methods [95] and DFT calculations, [96,97] its catalytic behavior is also typical of a well-defined catalyst: the initiation step corresponds to the cross-metathesis of the olefin and the neopentylidene ligand. In the case of propene, a 3:1 ratio of t-BuCH=CH 2 and t-BuCH= CHCH 3 is obtained, which is in agreement with the following model (Scheme 17): the favored reaction pathway corresponds to that in which interactions between the alkyl substituents of the metallacyclobutane are minimized, that is, pathway involving [1,3]-interactions > pathway involving [1,2]-interactions.…”

Surface versus Molecular Siloxy Ligands in Well‐Defined Olefin Metathesis Catalysts: [{(RO)3SiO}Mo(NAr)(CHtBu)(CH2tBu)]

“…In homogeneous catalysis, well-defined Mo complexes such as [(R F6 O) 2 Mo( = NAr)( = CHtBu)] [4][5][6][7] (R F6 = (CF 3 ) 2 (CH 3 )C) are much better catalysts than their Re equivalents [(R F6 O) 2 Re( CtBu)(=CHtBu)]. [8,9] However, preparing a supported equivalent to [(R F6 O) 2 Mo(=NAr)(=CHtBu)] has remained a challenge. [10][11][12][13][14][15] In surface organometallic chemistry, [16] the formation of a Mo alkylidene complex requires the use of welldefined Mo alkyl alkylidene molecular precursors, which have become available only recently as [Mo( = NAr)( = CHtBu)-(CH 2 tBu) 2 ] (2; Ar= 2,6-diisopropylphenyl).…”