Synthesis of Iridium(III) and Rhodium(III) Complexes Bearing C8-Metalated Theophylline Ligands by Directed C–H Activation

Chirality at Metal in a Linear [Ag(NHC)2]+ Complex: Stereogenic C-Ag-C Axis, Atropisomerism and Role of π-π Interactions

Chirality at the metal center is a well-established concept, exemplified by numerous four- and six-coordinated complexes. Here, a pioneering example of linear chirality-at-metal is described: [Ag(NHC)2]+ (NHC=N-heterocyclic carbene). In solution, stabilizing π-π interactions preserve the chiral information of the solid state. Consequently, a novel class of atropisomers is identified, whose stereogenicity arises from hindered rotation around a C-Ag-C axis, instead of a typical C-C bond.

Facile N9-Alkylation of Xanthine Derivatives and Their Use as Precursors for N-Heterocyclic Carbene Complexes

The xanthine-derivatives 1,3,7-trimethylxanthine, 1,3-dimethyl-7-benzylxanthine and 1,3-dimethyl-7-(4-chlorobenzyl)xanthine are readily ethylated at N9 using the cheap alkylating agents ethyl tosylate or diethyl sulfate. The resulting xanthinium tosylate or ethyl sulfate salts can be converted into the corresponding PF₆^- and chloride salts. The reaction of these xanthinium salts with silver(I) oxide results in the formation of different silver(I) carbene-complexes. In the presence of ammonia, ammine complexes [Ag(NHC)(NH₃)]PF₆ are formed, whilst with Et₂NH, the bis(carbene) salts [Ag(NHC)₂]PF₆ were isolated. Using the xanthinium chloride salts neutral silver(I) carbenes [Ag(NHC)Cl] were prepared. These silver complexes were used in a variety of transmetallation reactions to give the corresponding gold(I), ruthenium(II) as well as rhodium(I) and rhodium(III) complexes. The compounds were characterized by various spectroscopic methods as well as X-ray diffraction.

Mononuclear and dinuclear gold(i) complexes with a caffeine-based di(N-heterocyclic carbene) ligand: synthesis, reactivity and structural DFT analysis

Two gold(i) complexes with caffeine-based di(N-heterocyclic carbene) ligands were synthesised and fully characterised.