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A ?-diketiminate manganese catalyst for alkene hydrosilylation: substrate scope, silicone preparation, and mechanistic insight.


ABSTRACT: The dimeric ?-diketiminate manganese hydride compound, [(2,6-iPr2PhBDI)Mn(?-H)]2, was prepared by treating [(2,6-iPr2PhBDI)Mn(?-Cl)]2 with NaEt3BH. This compound was characterized by single crystal X-ray diffraction and found to feature high-spin Mn centres that exhibit strong magnetic coupling by EPR spectroscopy. Once characterized, [(2,6-iPr2PhBDI)Mn(?-H)]2 was found to mediate the hydrosilylation of a broad scope of alkenes at elevated temperature. Aliphatic alkenes were found to undergo anti-Markovnikov hydrosilylation, while the hydrosilylation of styrenes using [(2,6-iPr2PhBDI)Mn(?-H)]2 afforded Markovnikov's product. Importantly, this catalyst has also been employed for the cross-linking of industrially-relevant silicones derived from vinyl-terminated poly(dimethylsiloxane) and 1,2,4-trivinylcyclohexane with catalyst loadings as low as 0.05 mol%. To gain a mechanistic understanding of [(2,6-iPr2PhBDI)Mn(?-H)]2-catalyzed olefin hydrosilylation, 4-tert-butylstyrene was added to [(2,6-iPr2PhBDI)Mn(?-H)]2 and conversion to the monomeric Mn alkyl complex, (2,6-iPr2PhBDI)Mn(CH(CH3)(4- t BuPh)), was observed. Isolation of this secondary alkyl intermediate confirms that olefin insertion into the Mn-H bond dictates the observed regioselectivities. The importance of our mechanistic findings as they relate to recent advances in Mn hydrosilylation catalysis is described herein.

SUBMITTER: Mukhopadhyay TK 

PROVIDER: S-EPMC6182418 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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A β-diketiminate manganese catalyst for alkene hydrosilylation: substrate scope, silicone preparation, and mechanistic insight.

Mukhopadhyay Tufan K TK   Flores Marco M   Groy Thomas L TL   Trovitch Ryan J RJ  

Chemical science 20180815 39


The dimeric β-diketiminate manganese hydride compound, [(<sup>2,6-iPr2Ph</sup>BDI)Mn(μ-H)]<sub>2</sub>, was prepared by treating [(<sup>2,6-iPr2Ph</sup>BDI)Mn(μ-Cl)]<sub>2</sub> with NaEt<sub>3</sub>BH. This compound was characterized by single crystal X-ray diffraction and found to feature high-spin Mn centres that exhibit strong magnetic coupling by EPR spectroscopy. Once characterized, [(<sup>2,6-iPr2Ph</sup>BDI)Mn(μ-H)]<sub>2</sub> was found to mediate the hydrosilylation of a broad scope of  ...[more]

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