Bonding and Catalytic Application of Ruthenium N-Heterocyclic Carbene Complexes Featuring Triazole, Triazolylidene, and Imidazolylidene Ligands

Abstract

ABSTRACT. The first mixed normal/abnormal NHC ruthenium(II) complexes bearing triazole/imidazole based ligands are presented. The ruthenium complexes show differing coordination geometries depending on the ligand sphere and the coordination of the triazole. Two Ru(II) monocarbene complexes have been obtained, with a 2-imidazolylidene carbene and the 1,2,3-triazoles acting as neutral nitrogen donors. In addition, a tridentate Ru(II) complex featuring a normal 2-imidazolylidene as well as two abnormal 1,2,3-triazolylidene carbene moieties is described. Both structural motifs are evaluated in transfer hydrogenation (TH) of acetophenone, with the electron rich Ru(II) tri-NHC exhibiting the highest conversion.

Unexpected arene ligand exchange results in the oxidation of an organoruthenium anticancer agent: the first X-ray structure of a protein–Ru(carbene) adduct

“…The distance between the Ru and carbene-C of 2.06 Å is in a similar range as found in Ru(NHC) complexes. 34 During refinement it became evident that Arg14 was coordinated to the metal centre (Ru-N Z1 Arg14 2.22 Å) and was displaced by 4.43 Å compared to a previously published structure (PDB ID: 5V4G, overlapped in Fig. S3, ESI †).…”

“…The presence of the NHC ligand at the Ru centre may labilise the p-bound p-cymene, similar to the elongation effect NHC ligands have in complexes on bonds in trans position. 34 Consequently, the bound metallofragment at site I was identified as a [Ru(dmb)(OH x )Cl 2 ] fragment coordinated to the N e1…”

Mesoionic and Related Less Heteroatom-Stabilized N-Heterocyclic Carbene Complexes: Synthesis, Catalysis, and Other Applications

“…The silver carbene either reacts after isolation or more often just generated in situ with a variety of metal precursors and has been successfully applied for the synthesis of triazolylidene complexes with Pd­(II), ,− Ir­(I), − Ir­(III), ,− Ru­(II), ,,,,,− ,,,− Rh­(I), ,,,− Rh­(III), ,, Au­(I), ,,,,,− Cu­(I), −…”

“…This coordination mode is obtained in complexes with pincer ligands comprised of two triazolylidene fragments that are connected through a pyridine ( O ; M = Ru, ,,, Pt, and Fe) or a carbazole ( P ; M = Au, Ni, Cu, and Rh). A central imidazole unit gives a tris­(NHC) Ru complex Q , with a facially coordinating C,C,C- tridentate ligand. A similar bonding mode is accessible with a tris­(triazolylidene) borate ligand, as demonstrated with the nickel complex 67 and the manganese analogue ( 68 ; see Scheme ).…”

Carbohydrate-functionalized N-heterocyclic carbene Ru(ii) complexes: synthesis, characterization and catalytic transfer hydrogenation activity

“…N-Heterocyclic carbenes (NHCs) act as versatile ligands for various catalytic systems, 1 as well as for biological and materials applications. 2 Ruthenium complexes of NHCs, in particular, have shown a broad range of catalytic activity, [3][4][5][6] with application in olefin-metathesis, [7][8][9] transfer hydrogenation, [10][11][12][13][14][15][16][17][18] as well as oxidation of alcohols and amines, [19][20][21][22][23] and water. 24 1,2,3-Triazolylidenes have emerged as a particularly promising subclass of NHC ligands that are stronger σ-donors than Arduengo-type imidazolylidenes and easily accessible through Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) 'click' chemistry.…”