No abstract

[structure: see text] The monoquaternary product of 2,2'-biimidazole with iodobutane is an ionic liquid that acts as both the solvent and ligand for catalytic reactions. A new palladium complex was prepared by adding PdCl(2) to this ionic liquid to form a catalytic solution that is effective for Heck reactions with good recyclability.

The reaction between 1 equiv of the sterically encumbered lithium terphenyl Et 2 O‚LiC 6 H 3 -2,6-Trip 2 and PbBr 2 in diethyl ether afforded the organolead(II) halide compound {Pb(µ-Br)C 6 H 3 -2,6-Trip 2 } 2 (1) as orange crystals. Treatment of 1 with a stoichiometric amount of pyridine (py) gave the complex py‚Pb(Br)C 6 H 3 -2,6-Trip 2 (2) as yellow needles. The addition of 1 equiv of methylmagnesium bromide, tert-butyllithium, or phenyllithium to 1 resulted in the diorganolead(II) compounds Pb(R)C 6 H 3 -2,6-Trip 2 (R ) Me, 3; t-Bu, 4; or Ph, 5) in good yield. The compounds 3 and 5 are the first stable, monomeric lead(II) derivatives involving the simplest alkyl and aryl groups Me and Ph. Reaction of 1 with W(CO) 5 THF did not yield the expected plumbylene complex (CO) 5 W{Pb(Br)C 6 H 3 -2,6-Trip 2 }. Instead, the bridged plumbylyne species [{W(CO) 4 } 2 (µ-Br)(µ-Pb-C 6 H 3 -2,6-Trip 2 )] ( 6) was obtained in low yield. All compounds were characterized by X-ray crystallography, 1 H and 13 C NMR, IR, and UV-vis spectroscopy. 207 Pb NMR spectra of 3-5 were also obtained. The results demonstrate the effectiveness of the terphenyl ligand in creating a protected cavity at a site in which normally unstable moieties are stabilized against decomposition reactions.

Ionic liquids with pincer dicationic nuclei, 2a-6a and 2b-6b, were prepared from either 1,1′-methylenebis(imidazole) or 1,1′-methylenebis(1,2,4-triazole) via quaternization with alkyl or polyfluoroalkyl halides under classical or microwave irradiation conditions. Palladiumcatalyzed Heck cross-coupling reactions were performed successfully in the ionic liquid 3a. A single-crystal X-ray structure of a bis(N-heterocyclic carbene) complex of palladium ( 7) formed in the ionic liquid catalyst system supports its likelihood as the active catalyst.

The reaction of 2,6-(4-t-BuC 6 H 4 ) 2 C 6 H 3 Li with BH 2 Cl‚SMe 2 in hexane or Et 2 O solution affords the terphenyl-substituted unsymmetrical 9-borafluorene 1-(4-tert-butylphenyl)-7-tertbutyl-9-(bis-2,6-(4-tert-butylphenyl)phenyl)-9-borafluorene (1) in good to moderate yields. Addition of pyridine gives the colorless crystalline adduct 1‚py. Compound 1 is readily reduced to the deep red heteroaromatic dianionic (µ 2 -η 5 ,η 5 -1-(4-tert-butylphenyl)-7-tert-butyl-9-(bis-2,6-(4-tert-butylphenyl)phenyl)-9-borafluorenyl)bis(diethyl ether)dilithium ( 2) with excess lithium powder in Et 2 O solution. Reactions of the dianionic 2 with various metal salts leads to reduction of these salts, and bright yellow 1 is recovered in essentially quantitative yields. Compounds 1, 1‚py, and 2 were characterized by 1 H, 13 C, and 11 B NMR spectroscopy and compounds 1‚py and 2 also by single-crystal X-ray diffraction.