Surface‐Dependent Chemoselectivity in C−C Coupling Reactions. (14th May 2019)

• Record Type: Journal Article
• Authors: Chen, Zhi; Lin, Tao; Zhang, Liding; Zhang, Lei; Xiang, Bingxi; Xu, Hu; Klappenberger, Florian; Barth, Johannes V.; Klyatskaya, Svetlana; Ruben, Mario
• Is Part Of: Angewandte Chemie. Volume 131:Number 25(2019)
• Page Start: 8444
• Page End: 8449
• Publication Date: 2019-05-14
• Subjects: Alkene -- Alkine -- Chemoselektivität -- Kreuzkupplung -- Rastertunnelmikroskopie; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201900636
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: Surface‐confined covalent coupling reactions of the linear compound 4‐(but‐3‐en‐1‐ynyl)‐4′‐ethynyl‐1, 1′‐biphenyl (1 ), which contains one alkyne and one enyne group on opposing ends, have been investigated using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The reactions show a surface‐dependent chemoselectivity: on Au(111), compound 1 preferentially yields cyclotrimerization products, while on Cu(111), a selective coupling between the enyne and alkyne groups is observed. Linear, V‐shaped string formations combined with Y‐shaped bifurcation motifs result in a random reticulation on the entire surface. DFT calculations show that the C−H⋅⋅⋅π δ− transition state of the reaction between the deprotonated alkyne group and a nearby H‐donor of the alkene group plays a key role in the mechanism and high chemoselectivity. This study highlights a concept that opens new avenues to the surface‐confined synthesis of covalent carbon‐based sp–sp 2 polymers. Abstract : Gestricktes Nanonetz : Ein Molekül mit einer Alkin‐ und einer Enin‐Gruppe zeigt Chemoselektivität in Oberflächen‐C‐C‐Kupplungsreaktionen in Abhängigkeit vom Metallsubstrat. Cyclotrimerisierung des Alkins auf Au(111) und Kreuzkupplung zwischen der Enin‐ und der Alkingruppe auf Cu(111) führen zur Bildung von zweidimensionalen kovalenten Netzwerken, die experimentell beobachtet und durch DFT‐Rechnungen bestätigt werden.