Isolation and Characterization of Well‐Defined Silica‐Supported Azametallacyclopentane: A Key Intermediate in Catalytic Hydroaminoalkylation Reactions

Abstract

Intermolecular catalytic hydroaminoalkylation of unactivated alkene occurs with silica-supported azazirconacyclopropane [ Si À O À Zr(HNMe 2 )(h 2

Solid‐State NMR and DFT Studies on the Formation of Well‐Defined Silica‐Supported Tantallaaziridines: From Synthesis to Catalytic Application

“…Furthermore, a new band was observed at 1490 cm −1 and the small band of 1 visible at 1422 cm −1 disappeared in 2 . These bands correspond to vibration of the C−H bond of the CH 2 group formed in 2 . In comparison to [≡Si‐O‐Zr(HNMe 2 )(η 2 ‐NMeCH 2 )(NMe 2 )], the wavenumber of this CH 2 band is lower, as expected.…”

“…These results fueled interest in a better understanding of the reaction mechanism, with a view to improving the reactivity and selectivity of the catalysts. A series of mechanistic investigations have been reported including kinetic studies, isotope distribution studies, and solid‐state (SS) NMR experiments . The formation of metallaaziridine intermediates was postulated as the key step in the catalytic cycle.…”

“…The reactivity of the latter species was harnessed, and the surface monohydride [≡Si‐O‐Zr(HNMe 2 )(NMe 2 ) 2 H] was selectively isolated and shown to be an active catalyst for alkene hydrogenation . Additional studies revealed that [≡Si‐O‐Zr(HNMe 2 )(η 2 ‐NMeCH 2 )(NMe 2 )] was able to catalyze the hydroaminoalkylation of propylene with dimethylamide, albeit in modest yields …”

“…As eries of mechanistic investigationsh ave been reportedi ncluding kinetic studies, [9] isotope distribution studies, [2b] and solid-state (SS) NMR experiments. [16] The formation of metallaaziridine intermediates was postulated as the key step in the catalytic cycle. Such species have been formally elucidated in only af ew reports.…”

Imine Metathesis Catalyzed by a Silica-Supported Hafnium Imido Complex

“…A variety of examples of catalysis were observed with these complexes, including the hydroaminoalkylation of alkenes and the metathesis of imines, depending on the supported metal/nitrogen-containing-ligand combination, M-ή 2 NRCHR or M=NR, respectively. [3][4] The reported work on such catalysts is largely focused on imido or amido complexes (e.g., of molybdenum), [5][6] and the nitrogen-containing ligands were generally found to be mere spectators. But recent evidence of Zr=N surface fragments 3 performing imine metathesis catalysis triggered our interest in determining whether this reactivity is specific to zirconium or can be extended to other metal such as hafnium.…”