A β-diketiminate manganese catalyst for alkene hydrosilylation

Substrate scope, silicone preparation, and mechanistic insight

Tufan K. Mukhopadhyay, Marco Flores, Thomas L. Groy, Ryan Trovitch

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The dimeric β-diketiminate manganese hydride compound, [(2,6-iPr2PhBDI)Mn(μ-H)]2, was prepared by treating [(2,6-iPr2PhBDI)Mn(μ-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(μ-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(μ-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(μ-H)]2-catalyzed olefin hydrosilylation, 4-tert-butylstyrene was added to [(2,6-iPr2PhBDI)Mn(μ-H)]2 and conversion to the monomeric Mn alkyl complex, (2,6-iPr2PhBDI)Mn(CH(CH3)(4-tBuPh)), 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.

Original languageEnglish
Pages (from-to)7673-7680
Number of pages8
JournalChemical Science
Volume9
Issue number39
DOIs
Publication statusPublished - Jan 1 2018

Fingerprint

Hydrosilylation
Alkenes
Silicones
Manganese
Catalysts
Substrates
Styrenes
Regioselectivity
Magnetic couplings
Hydrides
Catalysis
Paramagnetic resonance
Single crystals
Spectroscopy
X ray diffraction
Hydrogen

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

A β-diketiminate manganese catalyst for alkene hydrosilylation : Substrate scope, silicone preparation, and mechanistic insight. / Mukhopadhyay, Tufan K.; Flores, Marco; Groy, Thomas L.; Trovitch, Ryan.

In: Chemical Science, Vol. 9, No. 39, 01.01.2018, p. 7673-7680.

Research output: Contribution to journalArticle

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abstract = "The dimeric β-diketiminate manganese hydride compound, [(2,6-iPr2PhBDI)Mn(μ-H)]2, was prepared by treating [(2,6-iPr2PhBDI)Mn(μ-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(μ-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(μ-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(μ-H)]2-catalyzed olefin hydrosilylation, 4-tert-butylstyrene was added to [(2,6-iPr2PhBDI)Mn(μ-H)]2 and conversion to the monomeric Mn alkyl complex, (2,6-iPr2PhBDI)Mn(CH(CH3)(4-tBuPh)), 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.",
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