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Light-Induced Rearrangement of Thioether-Substituted Phosphanide Ligands: Scope and Limitations of a Remarkable Isomerization

Lookup NU author(s): Dr Keith Izod, Dr Ewan Clark, Emeritus Professor Bill Clegg, Dr Ross Harrington

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Abstract

Treatment of the thioether-substituted secondary phosphanes R2PH(C6H4-2-SR1) [R2 = (Me3Si)2CH, R1 = Me (1PH), iPr (2PH), Ph (3PH); R2 = tBu, R1 = Me (4PH); R2 = Ph, R1 = Me (5PH)] with nBuLi yields the corresponding lithium phosphanides, which were isolated as their THF (1-5Pa) and tmeda (1-5Pb) adducts. Solid state structures were obtained for the adducts [R2P(C6H4-2-SR1)]Li(L)n [R2 = (Me3Si)2CH, R1 = nPr, (L)n = tmeda (2Pb); R2 = (Me3Si)2CH, R1 = Ph, (L)n = tmeda (3Pb); R2 = Ph, R1 = Me, (L)n = (THF)1.33 (5Pa); R2 = Ph, R1 = Me, (L)n = (12-crown-4)2 (5Pc)]. Treatment of 1PH with either PhCH2Na or PhCH2K yields the heavier alkali metal complexes [{(Me3Si)2CH}P(C6H4-2-SMe)]M(THF)n [M = Na (1Pd), K (1Pe)]. With the exception of 2Pa and 2Pb, photolysis of these complexes with white light proceeds rapidly to give the thiolate species [R2P(R1)(C6H4-2-S)]M(L)n [M = Li, L = THF (1Sa, 3Sa5Sa); M = Li, L = tmeda (1Sb, 3Sb5Sb); M = Na, L = THF (1Sd); M = K, L = THF (1Se)] as the sole products. The compounds 3Sa and 4Sa may be de-solvated to give the cyclic oligomers [[{(Me3Si)2CH}P(Ph)(C6H4-2-S)]Li]6 ((3S)6) and [[tBuP(Me)(C6H4-2-S)]Li]8 ((4S)8), respectively. A mechanistic study reveals that the phosphanide-thiolate rearrangement proceeds via intramolecular nucleophilic attack of the phosphanide center at the carbon atom of the substituent at sulfur. For 2Pa/2Pb competing intramolecular b-deprotonation of the n-propyl substituent results in the elimination of propene and the formation of the phosphanide-thiolate dianion [{(Me3Si)2CH}P(C6H4-2-S)]2−.


Publication metadata

Author(s): Izod K, Clark ER, Foster P, Percival RJ, Riddlestone IM, Clegg W, Harrington RW

Publication type: Article

Publication status: Published

Journal: Chemistry: A European Journal

Year: 2013

Volume: 19

Issue: 19

Pages: 6094-6107

Print publication date: 07/03/2013

ISSN (print): 0947-6539

ISSN (electronic): 1521-3765

Publisher: Wiley - V C H Verlag GmbH & Co. KGaA

URL: http://dx.doi.org/10.1002/chem.201203918

DOI: 10.1002/chem.201203918


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