Synthesis, characterization of novel half-sandwich iridium and rhodium complexes containing pyridine-based organochalcogen ligands

Synthesis, characterization, and catalytic activity of half‐sandwich ruthenium complexes with pyridine/phenylene bridged NHC = E (NHC = N‐heterocyclic carbene, E = S, Se) ligands

“…Pyridine/phenylene‐bridged NHC = E (E = S or Se) compounds: 2,6‐bis(1‐methylimidazole‐2‐thione)pyridine ( Bmtp ), 1,3‐bis(1‐methylimidazolyl‐2‐thione)benzene ( Bmtb ), and 1,3‐bis(1‐methylimidazolyl‐2‐selone)benzene ( Bmsb ) were prepared in one‐pot syntheses via the reactions of pyridine/phenylene‐bridged imidazolium dibromide derivatives with sulfur/selenium powder in the presence of K 2 CO 3 according to literature method. [ 9,28 ] The brown half‐sandwich complexes [Ru( p ‐cymene)( Bmtp )](PF 6 ) 2 ( 1a ), [Ru( p ‐cymene)( Bmtb )](PF 6 ) ( 1b ), and [Ru( p ‐cymene)( Bmsb )](PF 6 ) ( 1c ) were obtained by treatment of 2 equiv of the pyridine/phenylene‐bridged NHC = E ligand with [Ru( p ‐cymene)( μ ‐Cl)Cl] 2 in DCM for 16 hr at room temperature. The resulting solution was poured into excess aqueous KPF 6 and the brown precipitate was obtained by filtration and washed with water and ethyl ether with moderate yields (Scheme 1).…”

“…Furthermore, the 13 C NMR spectra of 1a–1c showed characteristic resonance C of C=S/C=Se at δ = 158.1 ppm ( 1a ), 158.8 ppm ( 1b ), and 158.4 ppm ( 1c ), in agreement with values reported for metal complexes with NHC = E (E = S, Se) adducts. [ 11,27,28,60 ] The ESI‐MS spectra of the complexes showed peaks at m/z = 269.5450 ( 1a ), 537.0552 ( 1b ), and 632.9596 ( 1c ), which are assigned to [M‐2PF 6 ] 2+ ( 1a ) and [M‐PF 6 ] + ( 1b and 1c ) ions, respectively.…”

“…The N‐heterocyclic carbene adducts 2,6‐bis(1‐methylimidazole‐2‐thione)pyridine ( Bmtp ), 1,3‐bis(1‐methylimidazolyl‐2‐selone)benzene ( Bmsb ), and [Ru( p ‐cymene)( μ ‐Cl)Cl] 2 were synthesized according to procedures described in the literature. [ 9,28,57 ] 1 H and 13 C NMR were recorded on a 400 MHz or 500 MHz NMR spectrometer at room temperature. Chemical shifts (δ) are given in ppm relative to internal TMS and are internally referenced to residual 1 H and 13 C solvent resonances.…”

“…[ 18–23 ] Modification of the NHC = E precursors and bridging groups allows chemists to fine‐tune the sterics, electronic properties, solubility, and catalytic activities of the metal complex. [ 24–28 ]…”

Synthesis and Crystal Structures of New 1,3-Disubstituted Imidazoline-2-thiones

“…Pyridine is known to be an effective solvent for this reaction in the triazole and thiazole series, often in the presence of triethylamine [14 -16]. The popular 'MeOH/K 2 CO 3 method' has been used for the synthesis of 1,3-dimethylimidazoline-2-thione [8,9], bridged bis(imidazoline-2-thiones) [17 -22], and also for multidentate ligands [23]. Very recently, mixed-donor bidentate ligands based on carbene and thione functions have been reported [24].…”