Synthesis and Reactivity of 16‐Electron Pentamethylcyclopentadienyl–Ruthenium(II) Complexes with Bis(imidazolin‐2‐imine) Ligands

Abstract

The 1,2-bis(imidazolin-2-imino)ethane ligands BL Me and BL iPr were prepared, in which the ability of the imidazolium moiety to effectively stabilize a positive charge leads to highly basic ligands with a strong electron-donating capacity. This feature is illustrated by the isolation of very stable half-sandwich 16-electron ruthenium complexes of the type [(η 5 -C 5 Me 5 )Ru(BL R )] + (1, R = Me; 2, R = iPr), which even resist coordination of the chloride counterion. Their inertness towards hard, π-basic ligands does not prevent these complexes from displaying high reactivity towards soft σ-donor/

Rare Earth and Alkaline Earth Metal Complexes with Me2Si‐Bridged Cyclopentadienyl‐Imidazolin‐2‐Imine Ligands and Their Use as Constrained‐Geometry Hydroamination Catalysts

“…Substrates 6a, 7a, and 8a, bearing bulky geminal substituents in the β-position to the amino group (Thorpe-Ingold effect), could be cyclized within a few minutes (entries 1-3 and 4-6). [38] By using less bulky substituents in the β-positions, significantly lower rates are observed for all catalysts (entries [10][11][12] …”

“…Yet again, these ligands attain their unique properties from their ability to effectively delocalize a positive charge over the imidazole moiety to produce compounds with considerably enhanced basicity and N-nucleophilicity. [9][10][11][12] For instance, the unusual stability of coordinatively unsaturated 16-electron ruthenium and molybdenum halfsandwich complexes supported by ethylene-bridged bis-(imidazolin-2-imine) ligands can be ascribed to the strongly π-basic nature of the novel bidentate ligands, [10] which also holds true for the high reactivity of copper(I) bis(imidazolin-2-imine) complexes and allows for effective CO 2 and O 2 fixation, C-Cl bond activation and Cu I disproportionation. [11] Recently, the pronounced electron donor properties of these ligands have also been demonstrated by the synthesis and structural characterization of lanthanide complexes containing a bis(imidazolin-2-imino)pyridine pincer ligand, which confirms that the imine moieties act as ylidic amidotype ligands upon metal complexation.…”

16‐Electron (Arene)ruthenium Complexes with Superbasic Bis(imidazolin‐2‐imine) Ligands and Their Use in Catalytic Transfer Hydrogenation

“…[13,14] Scheme 2. , respectively, and, because dicationic 16-electron half-sandwich ruthenium complexes are to the best of our knowledge unknown, we aimed at the stabilization of such complexes by the BL R ligands. The resulting complexes are also potential catalysts for various organic transformations, in view of the fact that 16-electron (arene)ruthenium complexes are frequently encountered as intermediates in ruthenium-catalyzed reactions.…”

3d Metal Complexes Supported by a Bis(imidazolin‐2‐imino)pyridine Pincer Ligand – Synthesis, Structural Characterisation, and Magnetic Properties

“…The reaction of TL tBu with metal dihalides gave complexes of the general formula [(TL tBu )-MX 2 ] (M = Mn, Fe, Co, Ni; X = Cl, Br). [7,8,9] In addition, copper(I) complexes containing the tridentate TL tBu ligand are very reactive and have a tendency to form stable, square-planar copper(II) complexes of the general type [(TL tBu -κ 3 )CuX], which have been applied successfully in aerobic CO 2 fixation (X = HCO 3 -κO), C-Cl bond activation and Cu I disproportionation reactions (X = Cl). Although [(TL tBu )MnCl 2 ] (1) is best described as distorted square-pyramidal, the complexes [(TL tBu )FeCl 2 ] (2) and [(TL tBu )CoCl 2 ] (3) show distorted tetrahedral geometries with the TL tBu ligand bound in a κ 2 fashion and one of its imidazolin-2-imine fragments not coordinated to the metal atom.…”