Golden crowns: cation binding by macrocyclic gold(I) crown ether derivatives

The polyether bis(alkynes) α,ω-bis(O-propargyl)triethylene glycol and α,ω-bis(O-4-propargyloxyphenoxy)triethylene glycol reacted with [AuCl(SMe₂)] in the presence of base to form the corresponding oligomeric gold(I) acetylide complexes (AuCCCH₂O(CH₂CH₂O)₃CH₂CCAu)_n and (AuCCCH₂OC₆H₄O(CH₂CH₂O)₃C₆H₄OCH₂CCAu)_n. These digold(I) diacetylide complexes reacted with diphosphine ligands to give macrocyclic digold(I) complexes of the type [Au₂(μ-CC)(μ-PP)], where CC is the diacetylide and PP is a diphosphine ligand. These digold(I) complexes bind the cations Li⁺, Na⁺, K⁺ and Cs⁺, as studied by electrospray mass spectrometry.     

Structure–Reactivity Relationships in the Hydrogenation of Carbon Dioxide with Ruthenium Complexes Bearing Pyridinylazolato Ligands

Pyridinylazolato (N–N′) ruthenium(II) complexes of the type [(N–N′)RuCl(PMe₃)₃] have been obtained in high yields by treating the corresponding functionalised azolylpyridines with [RuCl₂(PMe₃)₄] in the presence of a base. ¹⁵N NMR spectroscopy was used to elucidate the electronic influence of the substituents attached to the azolyl ring. The findings are in agreement with slight differences in the bond lengths of the ruthenium complexes. Furthermore, the electronic nature of the azolate moiety modulates the catalytic activity of the ruthenium complexes in the hydrogenation of carbon dioxide under supercritical conditions and in the transfer hydrogenation of acetophenone. DFT calculations were performed to shed light on the mechanism of the hydrogenation of carbon dioxide and to clarify the impact of the electronic nature of the pyridinylazolate ligands.     

Heterobimetallic Cuprates Consisting of a Redox‐Switchable,Silicon‐Based Metalloligand: Synthesis,Structures, and Electronic Properties

A series of bimetallic silyl halido cuprates consisting of the new tripodal silicon‐based metalloligand [κ³N‐Si(3,5‐Me₂pz)₃Mo(CO)₃]^? is presented (pz=pyrazolyl). This metalloligand is straightforwardly accessible by reacting the ambidentate ligand tris(3,5‐dimethylpyrazolyl)silanide ({Si(3,5‐Me₂pz)₃}^?) with [Mo(CO)₃(η⁶‐toluene)]. The compound features a fac‐coordinated tripodal chelating ligand and an outward pointing, “free” pyramidal silyl donor, which is easily accessible for a secondary coordination to other metal centers. Several bimetallic silyl halido cuprates of the general formula [CuX{μ‐κ¹Si:κ³N‐Si(3,5‐Me₂pz)₃Mo(CO)₃}]^? (X=Cl, Br, I) have been synthesized. The electronic and structural properties of these complexes were probed in detail by X‐ray diffraction analysis, electrospray mass spectrometry, infrared‐induced multiphoton dissociation studies, cyclic voltammetry, spectroelectrochemistry, gas‐phase photoelectron spectroscopy, as well as UV/Vis and fluorescence spectroscopy. The heterobimetallic complexes contain linear two‐coordinate copper(I) entities with the shortest silicon–copper distances reported so far. Oxidation of the anionic complexes in methylene chloride and acetonitrile solutions at ${E{{0\hfill \atop 1/2\hfill}}}$ =?0.60 and ?0.44 V (vs. ferrocene/ferrocenium (Fc/Fc⁺)), respectively, shows substantial reversibility. Based on various results obtained from different characterization methods, as well as density functional theory calculations, these oxidation events were attributed to the Mo⁰/Mo^I redox couple.