Evidence for Silica Surface Three- and Five-Membered Metallacycle Intermediates in the Catalytic Cycle of Hydroaminoalkylation of Olefins Using Single-Ti-Metal Catalysts

Abstract

The single-site silica-supported group IV metal amido complex [Ti(NMe 2 ) 4 ] gives the tris(amido)-supported fragment [(Si−O−)Ti(−NMe 2 ) 3 ], which transforms into a three-membered metallacycle (called a metallaaziridine) by an α-H transfer between two amido ligands. When the three-membered metallacycle reacts with 1-octene, it gives a five-membered metallacycle by insertion of the double bond into the M−C bond of the metallaziridine. These two metallacycles, key intermediates in the catalytic cycle of the hydroaminoalkylation of terminal olefins, were isolated and fully characterized following the surface organometallic chemistry (SOMC) concept and procedures. This paper shows that surface organometallic chemistry can be used to identify and fully characterize three-and five-membered metallacycles of Ti in the hydroaminoalkylation of olefins. Article pubs.acs.org/Organometallics

Readily available Ti-based in situ catalytic system for oxo/imido heterometathesis

“…We saw no evidence for the formation of metallaziridine species described by Scott and Basset for Ti(NMe 2 ) 4 /SiO 2 . 49,50 This is in agreement with Scott's observation that in the case of Ti(NEt 2 ) 4 /SiO 2 , such secondary transformations only occur at elevated temperatures. 49 Interestingly, similar observations were made for the Zr analogs, diethylamido complex being more stable 11 than the dimethylamide.…”

“…Grafting of Ti tetraamides on silica has been studied by many groups. [46][47][48][49][50][51][52] In agreement with these works, we found that treatment of SiO 2-700 (silica dehydroxylated at 700 °C) with a solution of Ti(NEt 2 ) 4 gave a yellow material 1 containing 0.22 ± 0.03 mmol Ti per g (consistent with quantitative grafting, the absence of unreacted Ti(NEt 2 ) 4 in NMR of washings, and full consumption of the uSiOH IR band of silica (Fig. S2, ESI †)) along with the liberation of ca.…”

Decoration, Characterization and Antimicrobial Activity Evaluation of Novel Nano‐Based 1,2‐Phenylenediamine Functionalized Maleic Anhydride‐Allylphenyl Ether Conjugate

“…The characteristic anhydride peak of poly[MA‐ alt ‐APE)] observed at 2.2 and 2.8–2.9 ppm is assigned to the −CH protons of the anhydride of the MA unit [65] . As a methylene bridge, CH 2 peaks of the APE unit were observed in the range of 1–2 ppm [66,67] . The characteristic aromatic ring protons on both APE (monosubstituted) and o ‐PDA (disubstituted) overlapped at 7.2 ppm and formed a sharp signal [7,64] .…”

“…[65] As a methylene bridge, CH 2 peaks of the APE unit were observed in the range of 1-2 ppm. [66,67] The characteristic aromatic ring protons on both APE (monosubstituted) and o-PDA (disubstituted) overlapped at 7.2 ppm and formed a sharp signal. [7,64] Confirmation of the mechanism of the conjugation reaction for poly[MA-alt-APE)]/o-PDA was performed by detecting the expected peak in the 5.0-8.5 ppm range due to the amide À NH (À CONHÀ ) in addition to other peak assignments.…”