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Metal alkyls programmed to generate metal alkylidenes by α-H abstraction: prognosis from NMR chemical shift

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Abstract

Metal alkylidenes, which are key organometallic intermediates in reactions such as olefination or alkene and alkane metathesis, are typically generated from metal dialkyl compounds [M](CH2R)2 that show distinctively deshielded chemical shifts for their α-carbons. Experimental solid-state NMR measurements combined with DFT/ZORA calculations and a chemical shift tensor analysis reveal that this remarkable deshielding originates from an empty metal d-orbital oriented in the M–Cα–Cα′ plane, interacting with the Cα p-orbital lying in the same plane. This π-type interaction inscribes some alkylidene character into Cα that favors alkylidene generation via α-H abstraction. The extent of the deshielding and the anisotropy of the alkyl chemical shift tensors distinguishes [M](CH2R)2 compounds that form alkylidenes from those that do not, relating the reactivity to molecular orbitals of the respective molecules. The α-carbon chemical shifts and tensor orientations thus predict the reactivity of metal alkyl compounds towards alkylidene generation.

Graphical abstract: Metal alkyls programmed to generate metal alkylidenes by α-H abstraction: prognosis from NMR chemical shift

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Publication details

The article was received on 24 Nov 2017, accepted on 04 Jan 2018 and first published on 05 Jan 2018


Article type: Edge Article
DOI: 10.1039/C7SC05039A
Citation: Chem. Sci., 2018, Advance Article
  • Open access: Creative Commons BY license
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    Metal alkyls programmed to generate metal alkylidenes by α-H abstraction: prognosis from NMR chemical shift

    C. P. Gordon, K. Yamamoto, K. Searles, S. Shirase, R. A. Andersen, O. Eisenstein and C. Copéret, Chem. Sci., 2018, Advance Article , DOI: 10.1039/C7SC05039A

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