Issue 7, 2018

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

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

Supplementary files

Article information

Article type
Edge Article
Submitted
24 Nov 2017
Accepted
04 Jan 2018
First published
05 Jan 2018
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2018,9, 1912-1918

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, 9, 1912 DOI: 10.1039/C7SC05039A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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