1,10-Phenanthroline Analogue Pyridazine-Based N-Heterocyclic Carbene Ligands

Abstract

Synthesis of a planar, π-conjugated pyridazine-based biscarbene is reported. Starting from 3,6-dimethylpyridazine, the bisimidazolium salt 1*2HPF 6 was prepared in a four-step synthesis by chlorination, amination, formylation, and cyclization. The free carbene 1 can be generated in situ by addition of base. Despite the rigid annelated tricycle, the carbene ligand turns out to be highly flexible upon coordination of transition-metal complexes. With silver(I) oxide or copper(I) oxide binuclear carbene complexes with a bridging coordination mode of the ligand are obtained. Transmetalation of both complexes to the respective gold complex is described. The bridging coordination mode of the carbene ligand is similar to that of 2,2′-bipyridine. Reaction of the bisimidazolium salt 1*2HPF 6 with potassium acetate and [RhCl(COD)] 2 leads to a mononuclear rhodium complex with the chelating binding mode of 1, resembling strongly the coordination properties of 1,10-phenanthroline.

Ni(NHC) Catalyzed Rearrangement of 1‐Acyl‐2‐vinylcyclopropanes: Tackling a Mechanistic Puzzle by Combined Experimental and Computational Studies

“…It should be noted, that also the use of only 10 mol‐% 16· HCl instead of 20 mol‐% in the reaction of endo ‐ 8c to 9c led to a decreased yield of 8 % (Scheme S2, Supporting Information). Also, bidentate NHC ligands led to decreased yields compared to the monodentate ligand 16· HCl (for details see Scheme S3, Supporting Information).…”

Electron‐Deficient Imidazolium Substituted Cp Ligands and their Ru Complexes

“…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.…”

Strategies for the construction of supramolecular assemblies from poly-NHC ligand precursors

“…The coordination number of copper(I) varies depending on the ligand employed [35,[43][44][45]. To date, a few copper(I) assemblies have been prepared via a straightforward one-pot strategy by metalation of designed polydentate imidazolium salts with Cu 2 O (as shown in Scheme 1, A).…”

“…To date, a few copper(I) assemblies have been prepared via a straightforward one-pot strategy by metalation of designed polydentate imidazolium salts with Cu 2 O (as shown in Scheme 1, A). However, this requires higher temperatures than those used to prepare silver(I) carbene assemblies [44,45]. Furthermore, copper(I) is unstable and easily oxidised to copper(II).…”