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Die eerste karbeenkomplekse van goud is reeds in 1971 deur Bonati en Minghetti gerapporteer. Verdere ontwikkelings na die 1980’s was stadig. Sedert 2007, toe die belangstelling in goudchemie reeds geweldig toegeneem het – en kort daarna amper dol geraak het – is die oorspronklike tipe asikliese diaminokarbeenkomplekse (ADK-komplekse) van goud weer te voorskyn gehaal, aangepas, beter gekarakteriseer en gebruik in teoretiese studies, luminessensie-ondersoeke, reaksies onder ongewone, hoë-energietoestande, stoïchiometriese omsettings, enkelkristalstudies en katalitiese reaksies waarin die goudatoom as reaktiewe sentrum optree. Die katalitiese ondersoeke konsentreer aanvanklik op chemo- en regioselektiewe transformasies, maar bereik uiteindelik ’n hoogtepunt met uiters suksesvolle enantioselektiewe sikliserings van geselekteerde alkynverbindings, waarin eers dikernige katalisatore en uiteindelik selfs monokernige ADK-goudkomplekse gebruik word. Sekere ADK-ligande beïnvloed die metaal elektronies en terselfdertyd stel dit die katalisator in staat om chirale inligting gedurende die aktiveringsproses optimaal aan die substraat oor te dra. In die lig van al hierdie inligting word nuwe voorstelle vir verdere ondersoek hier gemaak.
Trefwoorde: asikliese karbeenkomplekse van goud; geometriese isomere; kristalstrukture; homogene katalise; 1,6-enyne; enantioselektiewe reaksies; fotofisika; luminessensie; sigma-donorligande
The first carbene complexes of gold were reported by Bonati and Minghetti in 1971. Thereafter, for more than three decades, further developments were slow – until 2007, when there was an explosive increase in interest in gold chemistry. The original acyclic-diaminocarbene-type (ADC) complexes have recently been rejuvenated by improved characterisation, theoretical calculations, studies in luminescence, investigations of their stability and reactivity under high energy conditions, single crystal structure determinations, and their utilisation in stoichiometric and catalytic conversions in which the central gold atom functions as a reactive centre. The initial focus of the catalytic research was on chemo- and regioselective transformations, but it culminated in tremendously successful enantioselective cyclisations of selected alkyne compounds – initially with dinuclear gold catalysts, and ultimately even with mononuclear gold complexes. Subsequently, some ADC ligands were successfully designed to electronically influence the central gold atoms and, simultaneously, enable optimal transfer of chiral information to the substrate during the activation process. With all this new information at one’s disposal, new directions for future investigation are now proposed.
Keywords: Acyclic carbene complexes of gold; geometric isomers; crystal structures; homogeneous catalysis; 1,6-enynes; enantioselective reactions;photophysics; luminescence; sigma-donor ligands
Ontvang: 11 Oktober 2012
Geplaas: 28 November 2012
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