Premium
Observing Initial Steps in Gold‐Catalyzed Alkyne Transformations by Utilizing Bodipy‐Tagged Phosphine–Gold Complexes
Author(s) -
Vasiuta Roman,
Plenio Herbert
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201600264
Subject(s) - chemistry , bodipy , phosphine , cationic polymerization , fluorescence , photochemistry , catalysis , metal , salt (chemistry) , alkyne , quantum yield , medicinal chemistry , polymer chemistry , organic chemistry , physics , quantum mechanics
The Pd‐catalyzed reactions of 3‐chloro‐bodipy with R 2 PH (R=Ph, Cy) provide nonfluorescent bodipy–phosphines 3‐PR 2 –bodipy 3 a (R=Ph) and 3 b (R=Cy; quantum yield Φ <0.001). Metal complexes such as [AgCl( 3 b )] and [AuCl( 3 b )] were prepared and shown to display much higher fluorescence ( Φ =0.073 and 0.096). In the gold complexes, the level of fluorescence was found to be qualitatively correlated with the electron density at gold. Consequently, the fluorescence brightness of [AuCl( 3 b )] increases when the chloro ligand is replaced by a weakly coordinating anion, whereas upon formation of the electron‐rich complex [Au(SR)( 3 b )] the fluorescence is almost quenched. Related reactions of [AuCl( 3 b )] with [Ag]ONf)] (Nf= nonaflate) and phenyl acetylenes enable the tracking of initial steps in gold‐catalyzed reactions by using fluorescence spectroscopy. Treatment of [AuCl( 3 b )] with [Ag(ONf)] gave the respective [Au(ONf)( 3 b )] only when employing more than 2.5 equivalents of silver salt. The reaction of the “cationic” gold complex with phenyl acetylenes leads to the formation of the respective dinuclear cationic [{( 3 b )Au} 2 (CCPh)] + and an increase in the level of fluorescence. The rate of the reaction of [Au(ONf)( 3 b )] with PhCCH depends on the amount of silver salt in the reaction mixture; a large excess of silver salt accelerates this transformation. In situ fluorescence spectroscopy thus provides valuable information on the association of gold complexes with acetylenes.