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Regioselective metalation of a tertiary phosphine. Synthesis and structural characterization of an unusual tetramerie lithium phosphinomethanide

Lookup NU author(s): Dr Keith Izod, Paul O'Shaughnessy, Emeritus Professor Bill Clegg, Dr Stephen Liddle

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Abstract

The tertiary phosphine MeP(C6H4-2-CH2NMe2)2 (3) is conveniently prepared by the reaction of MePCl2 with Li(C6H4-2-CH2NMe2) in high yields. Treatment of 3 with n-BuLi in light petroleum yields the tetrameric lithium phosphinomethanide complex [Li{CH2P(C6H4-2-CH2NMe 2)2}]4·(PhMe)3 (5a) after recrystallization from toluene, whereas treatment of 3 with t-BuLi under similar conditions yields the benzyllithium complex [MeP(C6H4-2-CH2NMe2)-{C 6H4-2-CH(Li)NMe2}]2 (4). Complex 5a has been characterized by elemental analyses, multielement NMR spectroscopy, and X-ray crystallography. Complex 5 can also be accessed by moderate thermal treatment of 4 in toluene solution. The kinetics of this conversion were followed by 31P NMR spectroscopy and show a first-order dependence upon the concentration of 4 and are independent of the concentration of 3. Analysis of the temperature dependence of the reaction over the range T = 308-338 K yielded ΔH‡ = 68.1 ± 4.0 kJ mol-1 and ΛS‡ = -124 ± 30 J K-1 mol-1 for this reaction, consistent with the reaction proceeding via a concerted intramolecular H-Li exchange mechanism. © 2001 American Chemical Society.


Publication metadata

Author(s): Izod K, O'Shaughnessy P, Clegg W, Liddle ST

Publication type: Article

Publication status: Published

Journal: Organometallics

Year: 2001

Volume: 20

Issue: 4

Pages: 648-653

ISSN (print): 0276-7333

ISSN (electronic): 1520-6041

Publisher: American Chemical Society

URL: http://dx.doi.org/10.1021/om000876e

DOI: 10.1021/om000876e


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