DFT Study on Mechanism of Olefin Hydroalumination by XAlBuⁱ₂ in the Presence of Cp₂ZrCl₂ Catalyst. I. Simulation of Intermediate Formation in Reaction of HAlBuⁱ₂ with Cp₂ZrCl₂

Abstract

The mechanism of intermediate formation in the reaction of HAlBu i 2 with Cp 2 ZrCl 2 has been studied by DFT calculations. Stationary points have been localized on the potential energy surface of the reaction; enthalpy has been calculated for each of them at T ) 203 K. It was shown that the thermodynamically probable way of the process includes formation of a bridge bimetallic complex [Cp 2 ZrCl 2 • HAlBu i 2 ], which with dissociation gives Cp 2 ZrHCl. The subsequent coordination of Cp 2 ZrHCl with HAlBu i 2 provides the intermediate [Cp 2 ZrHCl • HAlBu i 2 ], which dimerizes into an experimentally observed complex [Cp 2 ZrH 2 • ClAlBu i 2 ] 2 . The competing stage of [Cp 2 ZrHCl • HAlBu i 2 ] interaction with HAlBu i 2 yields complex [Cp 2 ZrH 2 • ClAlBu i 2 • HAlBu i 2 ], which shows low activity in the olefin hydrometalation. As a result, the scheme of the intermediates' formations and transformations in the reaction of HAlBu i 2 with Cp 2 ZrCl 2 was proposed.

Structure and conformations of 2‐substituted and 3‐substituted alumolanes in polar solvents: a direct NMR observation

“…The 27 Al NMR spectra of 1‐ethyl‐3‐substituted alumolanes in THF exhibit signals in the δ Al range of 178–185 ppm (Table ), which is indicative of a four‐coordinate aluminum atom . The 27 Al NMR signals of alkylalanes (AlMe 3 , AlEt 3 ) in THF are located in the same region, but the half‐width of the signals is approximately twice smaller in comparison with alumolanes. There is a significant solvent effect on the 1 H, 13 C, and 27 Al NMR chemical shifts of OACs in the polar solvents.…”

Cobalt-bis(imino)pyridine complexes as catalysts for hydroalumination–isomerisation of internal olefins

“…15,[38][39][40][41][42] This may be one reason for the poor performance of this system in hydroalumination, relative to hydroboration. While the Co-hydride signal appears as a single peak, the ligand resonances show that two very similar species are present, a major and a minor component.…”

Alkene and Olefin Functionalization by Organoaluminum Compounds, Catalyzed with Zirconocenes: Mechanisms and Prospects

“…The structural types of the hydride Zr, Al-complexes, which could -complexes, using the quantum chemical methods [31,32], chemical kinetics [33] and NMR [22,23], showed that the reaction is a complex multi-step process (Scheme 4). The use of zirconocenes with less electron-donating and sterically hindered ligands provides the stable Zr, Al-hydride clusters L 2 Zr(μ-H) 3 ] n concentration, that is, realization the catalytic conditions, shifts the equilibrium toward low active large clusters into which the alkene insertion is hampered due to their competing intermolecular exchange with OAC oligomers.…”