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Issue 17, 2019
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Reactivity of an NHC-stabilized pyramidal hydrosilylene with electrophilic boron sources

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Abstract

Silylenes have become an indispensable tool for molecular bond activation. Their use for the construction of silicon–boron bonds is uncommon in comparison to the numerous studies on silylene-derived silicon-element bond formations. Herein we investigate the reactivity of the pyramidal NHC-coordinated hydrosilylene tBu3SiSi(H)LMe4 (1; NHC = N-heterocyclic carbene, LMe4 = 1,3,4,5-tetramethylimidazolin-2-ylidene) with various boron-centered electrophiles. The reaction of 1 with THF·BH3 or H3N→BH3 afforded the silylene complex 1→BH3 or the product of insertion of the silicon(II) atom into an N–H bond with concomitant dehydrogenation along the HN–BH moiety (2). The respective conversion of 1 with BPh3 yields 1→BPh3 which readily reacts with excess LMe4 to form the more stable complex LMe4→BPh3 with release of 1. Treatment of 1 with the haloboranes Et2O→BF3, BCl3, BBr3 and Me2S→BBr3 resulted in the formation of the Lewis acid base adducts 1→BX3 (X = F, Cl, Br) and an equilibrium with their auto-ionization products [12BX2]+[BX4] slowly develops. The ratio of 1→BX3 significantly increases with rising atomic number of the halide, thus 1→BF3 majorly transforms within hours while 1→BBr3 is near-quantitatively retained over time. Accordingly, the complex 1→BPhBr2 was isolated after conversion of 1 with PhBBr2.

Graphical abstract: Reactivity of an NHC-stabilized pyramidal hydrosilylene with electrophilic boron sources

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Publication details

The article was received on 09 Feb 2019, accepted on 03 Apr 2019 and first published on 03 Apr 2019


Article type: Paper
DOI: 10.1039/C9DT00608G
Dalton Trans., 2019,48, 5756-5765

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    Reactivity of an NHC-stabilized pyramidal hydrosilylene with electrophilic boron sources

    G. Dübek, D. Franz, C. Eisenhut, P. J. Altmann and S. Inoue, Dalton Trans., 2019, 48, 5756
    DOI: 10.1039/C9DT00608G

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