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Molecular and Silica‐Supported Mo and W d 0 Imido‐Methoxybenzylidene Complexes: Structure and Metathesis Activity
Author(s) -
Zhizhko Pavel A.,
Toth Florian,
Gordon Christopher P.,
Chan Ka Wing,
Liao WeiChih,
Mougel Victor,
Copéret Christophe
Publication year - 2019
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.201900190
Subject(s) - chemistry , metathesis , catalysis , salt metathesis reaction , medicinal chemistry , stereochemistry , crystallography , organic chemistry , polymerization , polymer
5‐Coordinated methoxybenzylidene complexes M(=NAr)(=CH−C 6 H 4 − o ‐OMe)(O t Bu F3 ) 2 (Ar=2,6‐ i Pr 2 C 6 H 3 ; t Bu F3 =CMe 2 (CF 3 )) of Mo ( 1m Mo ) and W ( 1m W ) were synthesized by cross‐metathesis from the corresponding neophylidene/neopentylidene precursors and o ‐methoxystyrene. 1m Mo and 1m W were grafted onto the surface of silica partially dehydroxylated at 700 °C to give well‐defined silica‐supported alkylidenes (≡SiO)M(=NAr)(=CH−C 6 H 4 − o ‐OMe)(O t Bu F3 ) (M=Mo ( 1 Mo ), W ( 1 W )). Supported methoxybenzylidene complexes were tested in metathesis of cis ‐4‐nonene, 1‐nonene, and ethyl oleate, and compared to their molecular precursors and supported classical analogs (≡SiO)M(=NAr)(=CHCMe 2 R)(O t Bu F3 ) (M=Mo, R=Ph ( 2 Mo ), M=W, R=Me ( 2 W )). Both grafted complexes 1 Mo and 1 W show significantly better performance as compared to their molecular precursors 1m Mo and 1m W but are less efficient than the classical 4‐coordinated alkylidenes 2 Mo and 2 W . Noteworthy, both 1 Mo and 1 W can reach equilibrium conversion in metathesis of cis‐ 4‐nonene at catalyst loadings as low as 50 ppm.