Aryne complexes of zerovalent metals of the nickel triad

Martin A. Bennett

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    15 Citations (Scopus)

    Abstract

    The chemistry of dihapto-aryne complexes of the zerovalent Group 10 metals of general formula [M(η2-aryne)L2] (M = Ni, Pd, Pt; L = various tertiary phosphines) is reviewed, with emphasis on the highly reactive nickel(0) compounds (aryne = benzyne, C6H4; 4,5-difluorobenzyne, 4,5-C6H2F2; 2,3-naphthalyne, 2,3-C10H6; L2 = 2 PEt 3, 2 PiPr3, 2 PCy3, dcpe). These can be generated by alkali metal reduction of the appropriate (2-halogenoaryl) nickel(ii) halide precursors, such as [NiX(2-XC6H4)L 2], which in turn are accessible by oxidative addition of the 1,2-dihaloarene to nickel(0) precursors such as [Ni(1,5-COD)2]. The X-ray structure of [Ni(η2-C6H4)(dcpe)] shows that this compound is a typical 16-electron Ni(0) (3d10) species in which benzyne acts as a 2-electron donor. Several unusual organonickel compounds derived from [Ni(η2-4,5-C 6H2F2)(PEt3)2] have been isolated recently, including [Ni2(μ-η2: η2-4,5-C6H2F2)(PEt 3)4], in which a 4-electron donor 4,5-difluorobenzyne is located at right-angles to a pair of nickel atoms. Free benzyne can be intercepted by both [Ni(η2-C2H4)(dcpe)] and [Pt(η2-C2H4)(PPh3) 2], but the resulting benzyne complexes rapidly insert benzyne to give the appropriate η11-2,2′-biphenylyl complexes. [Pt(η2-C6H4)(PPh 3)2] also undergoes rapid ortho-metallation to give [PtPh(2-C6H4PPh2)(PPh3)]. However, a trapping reaction has been used to make the first 1,4-benzdiyne complex, [{Ni(dcpe)2}2(μ-η22-1, 4-C6H2)] by treatment of the 4-fluorobenzyne complex [Ni(η2-4-FC6H3)(dcpe)] with LiTMP. The use of alkali metals in the preparation of the η2-benzyne complexes is avoided in a more recently developed procedure, which starts from (2-bromophenyl)boronic acid, and is based on SuzukiMiyaura coupling. This procedure has made accessible for the first time an aryne complex of palladium(0), [Pd(η2-C6H4)(PCy 3)2], and the labile nickel(0) complex [Ni(η2-C6H4)(PPh3)2]. The aryne-nickel(0) complexes Ni(η2-aryne)L2 (L 2 = 2 PEt3, dcpe) undergo sequential insertions into the aryne-metal bond with unsaturated molecules, such as CO, C2F 4, substituted alkynes, substituted diynes, alkynylphosphines, and alkynyl thioethers, often with considerable regioselectivity. After the reductive elimination of two nickel-carbon -bonds, a variety of interesting polycyclic compounds can be obtained.

    Original languageEnglish
    Pages (from-to)1066-1075
    Number of pages10
    JournalAustralian Journal of Chemistry
    Volume63
    Issue number7
    DOIs
    Publication statusPublished - 2010

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