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Issue 26, 2013
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sp–sp3 Coupling reactions of alkynylsilver cations, RC[triple bond, length as m-dash]CAg2+ (R = Me and Ph) with allyliodide

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Abstract

Alkynylsilver cations, RC[triple bond, length as m-dash]CAg2+ (where R = Me and Ph) have been prepared in the gas phase using multistage mass spectrometry experiments in a quadrupole ion trap mass spectrometer. Two methods were used: (i) electrospray ionisation (ESI) of a mixture of AgNO3 (in MeOH/H2O/acetic acid) and the alkyne carboxylic acid to yield the appropriate silver acetylide cations RC[triple bond, length as m-dash]CAg2+, via a facile decarboxylation of the RC[triple bond, length as m-dash]CCO2Ag2+ precursor; (ii) ESI of silver acetylides, RC[triple bond, length as m-dash]CAg, which yields a cluster of the type, [(RC[triple bond, length as m-dash]CAg)12Ag2Cl]+. Regardless of the method of preparation, these alkynylsilver cations, RC[triple bond, length as m-dash]CAg2+, undergo ion-molecule reactions with allyliodide to yield the ionic products Ag2I+ and [(RC[triple bond, length as m-dash]CCH2CH[double bond, length as m-dash]CH2)Ag]+. The CID spectrum of [(PhC[triple bond, length as m-dash]CCH2CH[double bond, length as m-dash]CH2)Ag]+ was compared to that of an authentic sample of the silver adduct of 5-phenyl-1-penten-4-yne. Both ions fragment to yield Ag+ and the radical cation, PhC[triple bond, length as m-dash]CCH2CH[double bond, length as m-dash]CH2+˙, confirming that C–C bond coupling has taken place in the gas phase. DFT calculations were carried out on these C–C bond coupling reactions for the system R = Me. The reaction is highly exothermic and involves the initial coordination of the allyliodide to both silver atoms, with the iodine coordinating to one atom and the alkene moiety coordinating to the other. The overall mechanism of C–C bond coupling involves oxidative addition of the allyliodide followed by reductive elimination of RC[triple bond, length as m-dash]CCH2CH[double bond, length as m-dash]CH2, to ultimately yield two sets of reaction products: (i) Ag2I+ and RC[triple bond, length as m-dash]CCH2CH[double bond, length as m-dash]CH2; and (ii) [(RC[triple bond, length as m-dash]CCH2CH[double bond, length as m-dash]CH2)Ag]+ and AgI.

Graphical abstract: sp–sp3 Coupling reactions of alkynylsilver cations, RC [[triple bond, length as m-dash]] CAg2+ (R = Me and Ph) with allyliodide

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Publication details

The article was received on 17 Sep 2012, accepted on 12 Nov 2012 and first published on 27 Nov 2012


Article type: Paper
DOI: 10.1039/C2DT32143B
Citation: Dalton Trans., 2013,42, 9462-9467
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    sp–sp3 Coupling reactions of alkynylsilver cations, RC[triple bond, length as m-dash]CAg2+ (R = Me and Ph) with allyliodide

    G. N. Khairallah, C. M. Williams, S. Chow and R. A. J. O'Hair, Dalton Trans., 2013, 42, 9462
    DOI: 10.1039/C2DT32143B

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