A Molecularly Defined, Grafted Olefin Metathesis Catalyst from Tris(neopentyl)‐nitridomolybdenum(VI)

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

“…[101,106] Access to well-defined imido Mo alkylidene complexes was also realized by reaction of the nitrido ligand in [Mo( N)A C H T U N G T R E N N U N G (CH 2 -t-Bu) 3 ] with the surface silanol of silica (Scheme 19). [107,108] The trisalkyl intermediate cannot be isolated and gives directly 23 www.asc.wiley-vch.de nols gives very stable trisalkylimidosiloxy complexes, which need to be heated at > 80 8C to loose 2,2-dimethylpropane to provide a highly unstable olefin metathesis catalyst. [108] Moreover, note that protonation of the nitrido ligand is not observed upon reaction of [Mo( N)A C H T U N G T R E N N U N G (O-t-Bu) 3 ] with surface siloxy ligands.…”

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

“…[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). [17][18][19] Since the surface of silica partially dehydroxylated at 700 8C (SiO 2-(700) ) can be compared to a bulky monodentate ligand, [16] we investigated the reaction of 2 with SiO 2-(700) in order to generate a well-defined supported olefin metathesis catalyst.…”

Reactivity differences between molecular and surface silanols in the preparation of homogeneous and heterogeneous olefin metathesis catalysts

“…The closest well-defined surface organometallic complex is [("SiO)Mo(@NH)-(@CHtBu)(CH 2 tBu)], which was prepared by reaction of [Mo("N)(CH 2 tBu) 3 ] (1) [26] and a silica partially dehydroxylated at 500°C. However, it has only been prepared by sublimation in small quantities due to the thermal instability of 1 [27]. Its promising activities in olefin metathesis lead us to develop a preparation procedure for larger quantities, to investigate the synthesis of the corresponding molecular complex [{(RO) 3 SiO}-Mo(@NH)(@CHtBu)(CH 2 tBu)], and to compare the corresponding surface vs. molecular complexes.…”