Catalytic activation of remote alkenes through silyl-rhodium(iii) complexes

Abstract

Tandem isomerization-hydrosilylation reaction is a highly valuable process able to transform mixtures of internal olefins, into linear silanes. Unsaturated and cationic hydrido-silyl-Rh(III) complexes have proven to be effective catalysts for...

Rhodium Complexes with a Pyridine-2-yloxy-silyl-Based N,Si-Ligand: Bonding Situation and Activity as Alkene Hydrogenation Catalysts

“…The 29 Si{ 1 H} NMR spectra show a double doublet resonance at δ 83.3 ppm ( 1 J Si–Rh ≈ 35 Hz, 2 J Si–P ≈ 9 Hz; 2a ), 78.7 ppm ( 1 J Si–Rh ≈ 30 Hz, 2 J Si–Rh ≈ 9 Hz; 2b ), 87.9 ppm ( 1 J Si–Rh ≈ 40 Hz, 2 J Si–P ≈ 9 Hz; 3a ), and 85.9 ppm ( 1 J Si–Rh ≈ 36 Hz, 2 J Si–P ≈ 9 Hz; 3b ). Therefore, the 29 Si chemical shift observed for complexes 2a , b and 3a , b (in the range of δ 78.7–87.9 ppm) is clearly low-field shifted in comparison with the 29 Si resonances (δ 41.2–50.7 ppm), recently reported for neutral Rh(III)-(κ 2 -NSi Ar ) (NSi Ar = NSi Me2Q , NSi Me2QMe , NSi Me2AC ) species (Figure ), but compares well with the value of 79.4 ppm found for Rh-{κ 2 -( naphySi )} species (Figure ). The 1 J Rh–Si values found for complexes 2a (35 Hz), 2b (30 Hz), 3a (42 Hz), and 3b (41 Hz) confirm the silyl character of the Rh–Si bond and compare well with those observed in the 29 Si{ 1 H} NMR spectra of [Rh(X)(κ 2 -NSi Me2OPy ) 2 ] species (X = Cl, δ 85.7 ppm, 1 J Si–Rh ≈ 37 Hz; X = κ 2 -O 2 CCF 3 , δ 86.2 ppm, 1 J Si–Rh ≈ 39 Hz) .…”

Air-Stable 14-Electron Rhodium(III) Complexes Bearing Si,N Ligands as Catalysts in Hydrolysis of Silanes

“…Assuming an electrophilic mechanism, as has been previously proposed, − the difference in reaction rate observed between neutral and cationic catalysts may be due to the easier accessibility of the substrate to the metal center in the case of the cationic complex or the stronger electrophilicity of the cationic complexes with respect to the neutral ones. On the other hand, the cationic complexes also show differences in reaction rate being 2-L1 more active than 2-L2 and 2-L3 .…”

“…Based on these precedents and using the silicon-based ligands previously synthesized in the group (Figure ), two highly stable putative 14-electron Rh­(III) complexes have been synthesized and characterized in solution (NMR, ESI-MS) and in the solid state (X-ray). Moreover, their catalytic activity and selectivity in the hydrolysis reaction of silanes have been discussed.…”

“…Proligands used in this work: 8-(dimethylsilyl)­quinoline ( L1 ), 8-(dimethylsilyl)-2-methylquinoline ( L2 ), and 4-(dimethylsilyl)-9-phenylacridine ( L3 ) …”

%VBur index and steric maps: from predictive catalysis to machine learning

“…There are different reasons, either because it blocks a coordination of an additional ligand, because it leaves the perfect cavity in the first coordination sphere around the metal to interact with the substrates, and actually, it is common then that the most sterically protected metal centre is the most effective catalytically. 237,238…”