title: Light-induced rearrangement of thioether-substituted phosphanide ligands: scope and limitations of a remarkable isomerization.
abstract: Treatment of the thioether-substituted secondary phosphanes R(2)PH(C6H4-2-SR(1)) [R(2) = (Me3Si)2CH, R(1) = Me (1PH), iPr (2PH), Ph (3PH); R(2) = tBu, R(1) = Me (4PH); R(2) = Ph, R(1) = 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 [R(2)P(C6H4-2-SR(1))]Li(L)n [R(2) = (Me3Si)2CH, R(1) = nPr, (L)n = tmeda (2Pb); R(2) = (Me3Si)2CH, R(1) = Ph, (L)n = tmeda (3Pb); R(2) = Ph, R(1) = Me, (L)n = (THF)1.33 (5Pa); R(2) = Ph, R(1) = 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 [R(2)P(R(1))(C6H4-2-S)]M(L)n [M = Li, L = THF (1Sa, 3Sa-5Sa); M = Li, L = tmeda (1Sb, 3Sb-5Sb); M = Na, L = THF (1Sd); M = K, L = THF (1Se)] as the sole products. The compounds 3Sa and 4Sa may be desolvated 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 by intramolecular nucleophilic attack of the phosphanide center at the carbon atom of the substituent at sulfur. For 2Pa/2Pb, competing intramolecular β-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-).
authors.affiliation: Main Group Chemistry Laboratories, School of Chemistry, Bedson Building, University of Newcastle, Newcastle upon Tyne, NE1 7RU, UK. k.j.izod@ncl.ac.uk
authors.forename: Keith
authors.initials: K
authors.lastname: Izod
authors.forename: Ewan R
authors.initials: ER
authors.lastname: Clark
authors.forename: Pamela
authors.initials: P
authors.lastname: Foster
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Percival
authors.forename: Ian M
authors.initials: IM
authors.lastname: Riddlestone
authors.forename: William
authors.initials: W
authors.lastname: Clegg
authors.forename: Ross W
authors.initials: RW
authors.lastname: Harrington