Well-defined azazirconacyclopropane complexes supported on silica structurally determined by 2D NMR comparative elucidation

Abstract

Grafting of Zr(NMe2)4 on mesoporous silica SBA-15 afforded selectively well-defined surface species [triple bond, length as m-dash]SiOZr(NMe2)(η2NMeCH2). 2D solid-state NMR ((1)H-(13)C HETCOR, Multiple Quantum) experiments have shown a unique structural rearrangement occurring on the immobilised zirconium bis methylamido ligand.

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

“…Interestingly, a small peak at 35 ppm ( 13 C SS NMR) and a shoulder at 2.5 ppm ( 1 H SS NMR) can be interpreted as one NMe 2 group in axial position . This result illustrates a slightly different reactivity than that observed in our previous studies on the grafting of [Zr(NMe 2 ) 4 ] on SBA 15‐(700) (formally d 0 8e) . In this case, the azametallacyclopropane fragment is formed spontaneously at room temperature to afford [≡Si‐O‐Zr(η 2 ‐NMeCH 2 )(NHMe 2 )NMe 2 ] (formally d 0 10e, like 1 ).…”

“…New bands appeared in the regions corresponding to ν (C‐H) (3000–2800 cm −1 ) and δ C−H (1500–1300 cm −1 ). They can be assigned to dimethylamine ligand vibrations (Figure ) . The combination and overtone bands of the silica (1990, 1867, and 1639 cm −1 ) remained unchanged (Figure ).…”

Mesoporous Silica-Supported Amidozirconium-Catalyzed Carbonyl Hydroboration

“…31 Group 4-catalyzed carbonyl hydrosilylations and hydrogenations are also known, 11,32−35 and although Schwartz's reagent catalyzes hydroboration of alkynes, 36 we are not aware of previous reports of zirconium-catalyzed hydroboration of carbonyls. In addition, the reaction of Zr(NMe 2 ) 4 and SBA-15 was recently reported to give an azazirconocyclopropane surface species, 37 as does a titanium amide on silica en route to a titanium imido. 38 Notably, the azazirconocyclopropane species reacts with hydrogen to give a zirconium hydride that catalyzes hydrogenation of olefins.…”

Imine Metathesis Catalyzed by a Silica-Supported Hafnium Imido Complex

“…The spectrum obtained for 1 exhibits two resonances, centered at 7 and 32 ppm. On the basis of its relative abundance, we tentatively assign the intense signal shifted downfield at 32 ppm to the 15 N resonances corresponding to the tricoordinated nitrogen sites of the (η 2 π-NMeCH 2 ) and (-NMe 2 ) functionalities. The weak upfieldshifted signal at 7 ppm is compatible with an NH(CH 3 ) 2 moiety, even after heat treatment -HNMe 2 remains on the surface.…”

“…This result is consistent with a methylene (CH 2 ) group in a 3-membered metallacycle. 15 Two-dimensional proton double-(DQ) and triple-quantum (TQ) correlation experiments were performed with 1. A strong autocorrelation peak was observed for the signal at 2.2 ppm in both the DQ and TQ spectra (appearing at 4.4 and 6.6 ppm in the ω1 dimensions, respectively), indicative of methyl protons ( Figure 2).…”