Metal alkyls programmed to generate metal alkylidenes by α-H abstraction: prognosis from NMR chemical shift - Université de Montpellier
Article Dans Une Revue Chemical Science Année : 2018

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

Résumé

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.

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hal-01710047 , version 1 (06-07-2020)

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Christophe Gordon, Keishi Yamamoto, Keith Searles, Satoru Shirase, Richard A Andersen, et al.. Metal alkyls programmed to generate metal alkylidenes by α-H abstraction: prognosis from NMR chemical shift. Chemical Science, 2018, 9 (7), pp.1912 - 1918. ⟨10.1039/c7sc05039a⟩. ⟨hal-01710047⟩
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