Isolierung neutraler mono‐ und dinuklearer Goldkomplexe von cyclischen Alkyl(amino)carbenen

Abstract

Das kleinste Stückchen Gold! Dank der Anwesenheit zweier cyclischer Alkyl‐(amino)carbene (CAACs) konnten Komplexe mit einem bzw. zwei Goldatomen in der formalen Oxidationsstufe 0 isoliert werden.

Trinuclear Gold Clusters Supported by Cyclic (alkyl)(amino)carbene Ligands: Mimics for Gold Heterogeneous Catalysts

“…Compound 3 was characterized by 1 H and 13 C NMR spectroscopy as well as by high‐resolution mass spectrometry. The 13 C NMR signal corresponding to the carbene carbon appears at 262.5 ppm, which is half‐way between those observed for gold(I) complexes 1 and 2 (237.4 and 230.4 ppm, respectively) and the recently reported neutral (CAAC menthyl )AuAu(CAAC menthyl ) complex17 (287.2 ppm), as is expected for a mixed‐valence gold(I)/gold(0) compound. Cluster 3 was found to be indefinitely stable in air and moisture both in the solid state and in solution; its melting point (240 °C (dec.)) is another indication of its high stability.…”

“…19 Similar to the analogous cluster bearing P( o‐ Tol) 3 ligands,20 6 has a pseudo‐tetrahedral geometry, and can be viewed as three [CAAC‐Au] + units, with strong aurophilic interactions,21 bound to a central O 2− . In 7 , the AuAu distances (2.6324(8)–2.6706(8) Å) are much shorter than in 6 (3.1669(3)–3.3149(3) Å), which is indicative of true covalent bonds; for comparison, a gold–gold distance of 2.552 Å was observed for the neutral (CAAC)AuAu(CAAC) complex 17. In 9 , the distance between the two gold atoms bearing CAACs (2.6604(4) Å) is slightly longer than the other AuAu bonds (2.6191(4) and 2.6219(4) Å), arguing for the stronger σ‐donor properties of CAACs, compared to triphenyl phosphine 9…”

Trinuclear Gold Clusters Supported by Cyclic (alkyl)(amino)carbene Ligands: Mimics for Gold Heterogeneous Catalysts

“…Compound 3 was characterized by 1 H and 13 C NMR spectroscopy as well as by high-resolution mass spectrometry. The 13 C NMR signal corresponding to the carbene carbon appears at 262.5 ppm, which is half-way between those observed for gold(I) complexes 1 and 2 (237.4 and 230.4 ppm, respectively) and the recently reported neutral (CAAC menthyl )AuÀAu(CAAC menthyl ) complex [17] (287.2 ppm), as is expected for a mixed-valence gold(I)/ gold(0) compound. Cluster 3 was found to be indefinitely stable in air and moisture both in the solid state and in solution; its melting point (240 8C (dec.)) is another indication of its high stability.…”

“…In 7, the AuÀAu distances (2.6324 (8)-2.6706(8) ) are much shorter than in 6 (3.1669(3)-3.3149 (3) ), which is indicative of true covalent bonds; for comparison, a gold-gold distance of 2.552 was observed for the neutral (CAAC)Au À Au-(CAAC) complex. [17] In 9, the distance between the two gold atoms bearing CAACs (2.6604 (4) ) is slightly longer than the other AuÀAu bonds (2.6191(4) and 2.6219(4) ), arguing for the stronger s-donor properties of CAACs, compared to triphenyl phosphine. [9] Owing to our ongoing interest in the gold-catalyzed functionalization of amines, [22] we chose to investigate the behavior of cluster 7 for the carbonylation of this class of compounds.…”

Excimer and Exciplex Formation in Gold(I) Complexes Preconditioned by Aurophilic Interactions

“…[36][37][38] Attempts to obtain stable complexes of Au 2 were unsuccessful for along time, [39,40] until the group of Bertrand achieved the synthesis of ab is(carbene) complex in 2013. [41] Using their powerful CAAC ligands,s table,c rystalline complexes (CAAC)AuÀAu(CAAC)w ere obtained, and the molecular structures could be determined (Scheme 3, right: L = CAAC). Surprisingly,t he Au À Au distance was found to be 2.5520 long.Quantum-chemical calculations performed in this work (EDA-NOCV) resulted in Au À Au distances for the free Au 2 molecule and its complex of 2.546 and 2.579 , respectively,indicating aslight weakening of the AuÀAu bond upon complexation.…”