Aluminum Amidinates: Insights into Alkyne Hydroboration
| Autor: | Claire J. Carmalt, Katie Hobson, Clare Bakewell |
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| Rok vydání: | 2021 |
| Předmět: | |
| Zdroj: | Inorganic Chemistry |
| ISSN: | 1520-510X 0020-1669 |
| DOI: | 10.1021/acs.inorgchem.1c00619 |
| Popis: | The mechanism of the aluminum-mediated hydroboration of terminal alkynes was investigated using a series of novel aluminum amidinate hydride and alkyl complexes bearing symmetric and asymmetric ligands. The new aluminum complexes were fully characterized and found to facilitate the formation of the (E)-vinylboronate hydroboration product, with rates and orders of reaction linked to complex size and stability. Kinetic analysis and stoichiometric reactions were used to elucidate the mechanism, which we propose to proceed via the initial formation of an Al-borane adduct. Additionally, the most unstable complex was found to promote decomposition of the pinacolborane substrate to borane (BH3), which can then proceed to catalyze the reaction. This mechanism is in contrast to previously reported aluminum hydride-catalyzed hydroboration reactions, which are proposed to proceed via the initial formation of an aluminum acetylide, or by hydroalumination to form a vinylboronate ester as the first step in the catalytic cycle. This work focuses on the synthesis and characterization of a series of aluminum amidinate hydride and alkyl complexes. The compounds have been studied as hydroboration catalysts for the reaction of HBpin and phenylacetylene, and detailed kinetic and mechanistic investigations were carried out to elucidate possible reaction mechanisms. We propose the reaction to proceed via a HBpin adduct, in contrast to related literature on aluminum-catalyzed hydroboration reactions. |
| Databáze: | OpenAIRE |
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