Cyclic (Alkyl)- and (Aryl)-(amino)carbene Coinage Metal Complexes and Their Applications

Abstract

Cyclic (alkyl)-and (aryl)-(amino)carbenes (CAACs and CAArCs) are stronger sdonors and p-acceptors than imidazol-2-ylidenes and imidazolidin-2-ylidenes, the well-known Nheterocyclic carbenes (NHCs). Consequently, they form strong bonds with coinage metals, and stabilize both low and high oxidation states. This Focus Review shows that CAACs and CAArCs have allowed for the isolation of copper and gold complexes which were believed to be only transient intermediates. This has not only allowed for a better understanding of the mechanism of known processes but has also led to the development of novel coinage metal-catalyzed reactions.In addition to their role in homogeneous catalysis, CAAC and CAArC coinage metal complexes have recently found applications in medicinal chemistry, as well as in materials science. When possible, the performance of CAAC and CAArC ligands are compared with those of classical NHCs. 2 CONTENTS 1. Introduction 2. Coordination Chemistry of Cyclic (Alkyl)-and (Aryl)-(Amino)carbenes with Coinage Metals 2.1. Synthesis of (CAAC)MCl (M = Cu, Ag, Au) Complexes 2.2. Synthesis of Various Gold(I) and Gold(III) Complexes from (CAAC)AuCl and (CAAC)AuOH 2.3. Synthesis of (CAAC)CuH Complexes 2.4. Synthesis of CAAC Coinage Metal Alkene, Alkyne, and Aryl p-Complexes 2.5. Synthesis of CAAC Coinage Metal PCO Complexes 2.6. Synthesis of CAAC Coinage Metal(0) Complexes 2.7. Synthesis of CAAC Coinage Metal Clusters 2.8. Synthesis of HemilabileCAAC-Gold(I) and (III) Complexes. Oxidative addition at Gold(I) 2.9. Coordination Chemistry of CAAC-6 and BiCAAC 2.10. Synthesis of Saturated Abnormal Carbene and Cyclic (Aryl)(amino)carbene Coinage Metal Complexes 3. Cyclic (Alkyl)(Amino)carbene Coinage Metal Complexes in Catalysis 3.1. Catalytic Cross-Coupling of Two Unsaturated Carbon Centers Leading to Allenes 3.2. Gold Catalyzed Hydroamination of Alkynes and Allenes, and Hydroammoniumation and Methylamination of Alkynes3.3. (CAAC)-Mono-and -Bis-(copper)acetylide Complexes in Catalysis. 3.4. (CAAC) Coinage Metals for the Activation of Small Molecules 3.4.1. (CAAC)CuBH4 Complexes for the Catalytic Hydrolytic Dehydrogenation of BH3NH3 and for the Reduction of CO2 into Formate with H2. 3.4.2. Trinuclear (CAAC) Gold Clusters as Catalysts for the Carbonylation of Amines 3.5. Miscellaneous 3.5.1. (CAAC) Gold and Copper Catalysts for the Hydroarylation of Styrene with Anilines 3.5.2. (CAAC)Gold(I) Complexes in Gold/Palladium Dual Catalysis 3.5.3. (CAAC) Gold(III) Complexes in Migratory Insertion of Carbenes into Au(III)-C Bonds. 3.6. Chiral CAAC Ligands in Enantioselective Catalysis 4. Biological Applications of Cyclic (Alkyl)-and (Aryl)-(Amino)carbene Coinage Metal Complexes 5. Optoelectronic Applications of Cyclic (Alkyl)(amino)carbene Coinage Metal Complexes 6.

Nickel‐Catalyzed Intramolecular 1,2‐Aryl Migration of Mesoionic Carbenes (iMICs)

“…( 4 a – f )X were characterized by NMR spectroscopy, mass spectrometry, and X‐ray diffraction studies (see the Supporting Information). Selenium compounds have proven appropriate candidates to analyze the electronic properties of singlet carbenes [3, 4, 17] . 6 a and 6 b were prepared by the treatment of ( 4 a )PF 6 and ( 4 b )PF 6 with Se powder and KN(SiMe 3 ) 2 , respectively (Scheme 2).…”

Nickel‐katalysierte intramolekulare 1,2‐Aryl‐Wanderung von mesoionischen Carbenen (iMICs)

“…( 4 a – f )X wurden durch NMR‐Spektroskopie und Massenspektrometrie sowie Röntgenbeugungsexperimente charakterisiert (siehe Hintergrundinformationen). Selen‐Carbenaddukte sind für die Bestimmung elektronischer Eigenschaften von Carbenen von erheblicher Bedeutung [3, 4, 17] . 6 a und 6 b wurden durch In‐situ‐Erzeugung der S‐iMICs ( 5 a , b ) in Gegenwart eines Überschusses an Selenpulver hergestellt (Schema 2).…”

Impact of the macrocyclic structure and dynamic solvent effect on the reactivity of a localised singlet diradicaloid with π-single bonding character

“…For example, the isolation and fundamental understanding of carbenes enable their practical application in chemical synthesis. [1][2][3][4][5][6][7][8][9][10][11][12][13] Although much effort was devoted to proving the existence and exploring the role of singlet diradicals, key intermediates in homolytic bond cleavage, [14][15][16][17][18][19][20][21] in chemical reactions over the last century, important aspects remain unexplored. Diradicaloids, singlet diradicals with closed-shell character, 22 have attracted signicant attention not only because of their reactivity, but also due to their unique properties, which stem from the borderline character between open-and closed-shell molecules.…”