Selective di- and monochlorination of pyridazine-annelated bis(imidazolium) salts

Abstract

A synthetic route for the selective di- and monochlorination of pyridazine annelated bis(imidazolium) salts at the formamidinium moieties with trichloroisocyanuric acid (TCCA) is presented. Due to the steric hindrance, the molecular structure of the dichlorobis(imidazolium) salt shows a pronounced torsion from planarity as well as a deviation of the C–Cl bond vectors from the ideal bisecting line of the respective NCN angles such as to avoid each other. The monochlorinated bis(imidazolium) salt is free of steric hindrance and therefore shows less deviation from the parent bis(imidazolium) salt. In the presence of acetate the chloroimidazolium salt acts as a chlorination agent for acetate leading to formation of acetyl chloride and the respective urea.

Electron‐Deficient Imidazolium Substituted Cp Ligands and their Ru Complexes

“…To obtain also a 1,2‐substitution pattern of a di(imidazolium) Cp, we reacted the di(chloroimidazolium) salt 8 [12, 27] with two equivalents of LiCp or NaCp (see Scheme 5). In both cases, full conversion was obtained within one hour and the desired product was detected, but some brown impurities impeded its isolation.…”

“…Melting points were measured using aB üchi Melting Point M-560. UV/VIS spectra were recorded with aJ asco V-770 UV/Visible/NIR spectrophotometer.1 ,3,4,5-tetramethylimidazolin-2-ylidene, [20] Cp*H, [41] [RuCp*Cl 2 ] n , [42] [RuCp*(CH 3 CN) 3 ](PF 6 ), [43] thallium cyclopentadienide, [44] N,N'-di(n-propyl)-1,8-dichlorodiimidazo[1,5-b:5',1'-f]pyridazi-nium hexafluorophosphate( 8), [27,45] B(C 6 F 5 ) 3 [44,[46][47][48] and Li[B(C 6 F 5 ) 4 ]•2.5Et 2 O [49] were synthesized according to the published procedure. nBuLi, dicyclopentadiene, hexachloroethane, lithium bis(trimethylsilyl)amide, potassium hexafluorophosphate and deuterated water were purchased and used without further purification.…”

“…To obtaina lso a1 ,2-substitutionp attern of ad i(imidazolium) Cp, we reacted the di(chloroimidazolium) salt 8 [12,27] with two equivalents of LiCp or NaCp (see Scheme 5). In both cases,f ull conversion was obtained within one houra nd the desired product wasd etected, but some browni mpurities impeded its isolation.T herefore, we used the less nucleophilic thallium(I) cyclopentadienide and after two days full conversion at no apparents ide reactions was achieved( NMR).…”

Generation of Annelated Dicarbenes and Their Alkali-Metal Chelate Complexes in Solution: Equilibrium between Hetero- and Homoleptic NHC Lithium Complexes

“…The bite angle C1–Li–C8 is 80.1°, which is a value also found for vegi R complexes of transition-metal complexes. ,, The C1–C8 carbene distance of 2.89 Å is only slightly shorter than the value for the imidazolium salt 1b (3.04 Å) and the calculated value (DFT) for the free carbene 5b (2.98 Å) (see the Supporting Information). It lies right within the broad range of 2.67–3.26 Å observed for this ligand system so far . The lithium ion is not situated on the bisecting line of the N–C–N angles but lies 24.0° toward the center (Figure , right).…”