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Issue 38, 2010
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N-Heterocyclic carbene stabilized adducts of alkyl magnesium amide, bisalkyl magnesium and Grignard reagents: trapping oligomeric organo s-block fragments with NHCs

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Abstract

Developing N-heterocyclic carbene (NHC) chemistry of simple organomagnesium compounds, this study reports the synthesis, X-ray crystallographic, and NMR spectroscopic characterization of three such new carbene complexes. The 1 : 1 alkyl magnesium amide : carbene complexes nBuMg(TMP)·IPr 1 and nBuMg(HMDS)·IPr 2 both exist as mononuclear complexes in the crystal but differ in solution as 2 remains intact whereas 1 undergoes a dynamic exchange involving partial decoordination of IPr [TMP is 2,2,6,6-tetramethylpiperidide; IPr is 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene); HMDS is 1,1,1,3,3,3-hexamethyldisilazide]. Reaction of commercial nBu2Mg with IPr surprisingly produced the organoaluminium carbene complex nBu3Al·IPr, 3, which also forms a simple mononuclear structure in the crystal. The presence of the Al could be traced to the deliberate addition of a small quantity of Et3Al as a stabilizing agent in the commercial nBu2Mg reagent. Repeating this reaction with Al-free nBu2Mg afforded the hemisolvated carbene complex nBu8Mg4·2IPr, 4, the stoichiometry of which is dictated by its structure rather than by that used in the initial reaction mixture. The molecular structure of 4 is tetranuclear with a linear chain of 4 Mg centres bridged by nBu ligands and capped at each end by terminal nBu and IPr ligands. Synthesized by treating the Grignard reagent nBuMgCl with IPr, nBuMgCl·IPr, 5, forms a cyclodimer structure with chloro bridges and terminal nBu and IPr ligands.

Graphical abstract: N-Heterocyclic carbene stabilized adducts of alkyl magnesium amide, bisalkyl magnesium and Grignard reagents: trapping oligomeric organo s-block fragments with NHCs

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Publication details

The article was received on 21 Jun 2010, accepted on 04 Aug 2010 and first published on 23 Aug 2010


Article type: Paper
DOI: 10.1039/C0DT00693A
Citation: Dalton Trans., 2010,39, 9091-9099
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    N-Heterocyclic carbene stabilized adducts of alkyl magnesium amide, bisalkyl magnesium and Grignard reagents: trapping oligomeric organo s-block fragments with NHCs

    A. R. Kennedy, R. E. Mulvey and S. D. Robertson, Dalton Trans., 2010, 39, 9091
    DOI: 10.1039/C0DT00693A

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