The reactivity of gallium-(i), -(ii) and -(iii) heterocycles towards Group 15 substrates: Attempts to prepare gallium–terminal pnictinidene complexes

Robert J. Baker, Cameron Jones, David P. Mills, Damien M. Murphy, Evamarie Hey-Hawkins, Robert Wolf

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Abstract

The reactivity of a series of Ga(i), Ga(ii) and Ga(iii) heterocyclic compounds towards a number of Group 15 substrates has been investigated with a view to prepare examples of gallium–terminal pnictinidene complexes. Although no examples of such complexes were isolated, a number of novel complexes have been prepared. The reactions of the gallium(i) N-heterocyclic carbene analogue, [K(tmeda)][:Ga([N(Ar)C(H)]2)] (Ar = 2,6-diisopropylphenyl) with cyclo-(PPh)5and PhN═NPh led to the unusual anionic spirocyclic complexes, [(κ2P, P′-(PhP)4)Ga([N(Ar)C(H)]2)]and [(κ2N, C-PhNN(H)(C6H4))Ga([N(Ar)C(H)]2)], via formal reductions of the Group 15 substrate. The reaction of the digallane(4), [Ga([N(Ar)C(H)]2)]2, with (Me3Si)N3afforded the paramagnetic, dimeric imido–gallane complex, [([N(Ar)C(H)˙]2)Ga(μ-N(SiMe3))]2, via a Ga–Ga bond insertion process. In addition, the new gallium(iii) phosphide, [GaI(P(H)Mes*)([N(Ar)C(H)]2˙)], Mes* = C6H2But3-2,4,6; was prepared and treated with diazabicycloundecane (DBU) to give [Ga(DBU)(P(H)Mes*)([N(Ar)C(H)]2)], presumably via a gallium–terminal phosphinidene intermediate, [Ga(═PMes*)([N(Ar)C(H)]2˙)]. The possible mechanisms of all reactions are discussed, all new complexes have been crystallographically characterised and all paramagnetic complexes have been studied by ENDOR and/or EPR spectroscopy.

Original languageEnglish
Pages (from-to)64-72
Number of pages9
JournalDalton Transactions
Volume6
Issue number2
DOIs
Publication statusPublished - 26 Oct 2005

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