Introducing Potential Hemilability into “Click” Triazoles and Triazolylidenes: Synthesis and Characterization of d⁶‐Metal Complexes and Oxidation Catalysis

Abstract

Hemilabile ligands are known to impart remarkable properties to their metal complexes. Herein, we present arene half‐sandwich complexes of RuII, OsII, and IrIII with “click”‐derived 1,2,3‐triazole (L1) and 1,2,3‐triazol‐5‐ylidene (L2) ligands containing a potentially hemilabile thioether donor. Structural elucidation of the complexes revealed localization of double bonds within the triazole in L1 and a delocalized situation within the triazolylidene ring of L2. For complexes with L1, unusual coordination occurs through the less basic nitrogen “N2” of the 1,2,3‐triazole. All complexes were applied for the catalytic oxidation of benzyl alcohol to benzaldehyde using N‐methylmorpholine N‐oxide as sacrificial oxidant. Furthermore, oxidation of diphenylmethanol to benzophenone was also achieved by using low catalyst loadings in very good yields. These are rare examples of OsII–triazole, as well as of OsII–triazolylidene complexes with “click”‐derived ligands.

RuII, OsII, and IrIII Complexes with Chelating Pyridyl–Mesoionic Carbene Ligands: Structural Characterization and Applications in Transfer Hydrogenation Catalysis

“…In contrast to the Ir complexes (probably due to lower steric demands of the Cym ligand) the OsCym(cent) bond lengths are not affected by additional substituents in the para position of the phenyl ring. The C1Os1 distance are 2.021(8) Å and 2.037(7) Å (Os‐ 1 and Os‐ 3 ) thus being in the expected range and consistent with previously reported complexes 6e. The Os1N4 bond lengths are slightly longer being 2.129(6) Å and 2.119(6) Å for Os‐ 1 and Os‐ 3 .…”

“…Secondly, in the 13 C NMR spectra, all of the complexes showed resonances typical for the carbene complexes, for example, at 156.7 ppm and 152.8 ppm for Os‐ 1 and Ir‐ 1 , respectively, which fits well with the previously reported complexes 6d. e We were also able to observe a correlation between the appearance of the carbene resonance in the 13 C spectra and the substitution on the alkyne part of the triazolylidene. However, this is a very small influence.…”

Synthesis and molecular studies of half-sandwich arene ruthenium and Cp*Rh/Cp*Ir complexes containing (3-picolyl)thiourea derivatives as N,S-bidentate donor ligands

“…Furthermore the distances between metal and centroid of arene/Cp* ring are in range 1.678-1.797 Å , while the M-Cl bond lengths are in the range of 2.3932-2.4212 Å . Both sets of values are close to those found in related complexes reported in the literature [28][29][30][31][32].…”

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.…”

“…49,50 Bifunctional NHC ligands have shown promise in a range of catalytic transformations including hydrogenations, giving rise to increased catalytic activities when compared to more classical analogs. 13,17,23,[51][52][53][54][55] The use of carbohydrate motifs in homogenous transition metal catalysts has attracted considerable attention, particularly for introducing chirality and water solubility. Several complexes with carbohydrate-based phosphine and phosphinite ligand scaffolds have shown excellent performance in asymmetric catalysis.…”