Imidazoline, complexes with

Gold(I) complexes with thiones are numerous and have several stoichiometries. The homoleptic [AuL2]+ have been obtained for L = imidazoline-2-thione,3029 4-amino-3-methyl-l,2,4-triazoline-5-thione 1560),3030 A -R-1,3-imidazoline-2-thione (R = Pr, Et),3031,3032 l,3-thiazoline-2-... 

Chloride dioxide (CIO2) forms red charge-transfer complexes with piperidine and imidazoline nitroxyl radicals that slowly transform into oxoammonium salts. ... 

Some bidentate bis(imidazolin-2-ylidene)s 18 have been used for the preparation of complexes with chelating dicarbene ligands [75-80]. The synthesis, properties, and coordination chemistry of tripodal tris(imidazolin-2-ylidene) ligands like 19... 

Additional factors which lead to an increased stability of the carbene complexes towards reductive ehmination are the type of NHC ligand and the NA -substitution pattern. The stability of NHC complexes depends strongly on the electronic situation at the carbene center. The oxidative addition of p-tolyl chloride to linear Pd° complexes bearing two unsaturated imidazolin-2-ylidenes (type 5, Fig. 6) or two saturated imidazolidin-2-ylidenes (t3q>e 7, Fig. 6) proceeds readily. The Pd complex with the imidazolin-2-yhdene ligands is stable, while the one with the imida-zolidin-2-ylidene ligands reductively ehminates the C2-arylated imidazolidinium salt [134]. 

The imine bond in 2-imidazolines reacts with Fisher carbenes under irradiation (Scheme 144). Low yields were obtained with monosubstituted imidazolines 608a-c due to thermal decomposition of the substrates under the reaction conditions. Optically active 4,4-disubstituted A -imidazolines 608d-e form azapenams (609d, 610e, 611) with (methoxymethylcarbene)chromium complex in good yields and high diastereoselectivity. The electronic nature of RVR clearly influences the sense of diastereoselectivity (609 vs. 610, 611) <1977JOC3586>. 

In another example, the hydrogenation of the azapenam (55,6/ )-6-methoxy-2,2,6-trimethyl-l,4-diazabicyclo[3.2.0]heptan-7-one (154), prepared by reaction of a pentacarbonyl chromium carbene complex with liV-Boc-4,4-dimethylimidazoline, in the presence of 1.1 equiv. of racemic camphor sulfonic acid resulted in the cleavage of the Boc group and ring expansion of the azapenam to hexahydro-3,3,6-trimethyl-6-methoxy-5//-l,4-diazepin-5-one (155) in 71% yield <92JA5010>. It was pointed out that the ready availability of a variety of substituted chromium carbene complexes and imidazolines would make this a general route to this class of diazepine. 

The synthesized zwitterionic iridium complexes containing various chiral P, N ligands with imidazoline or oxazoline were used as precatalysts for the asymmetric hydrogenation of unfunctionalized olefins. The cationic complexes with fluorinated borates as anions were superior catalysts in dichloromethane, whereas the iridium betaines were good catalysts in pure hydrocarbons. ... 

A similar route was used by us to synthesize pincer complexes with the monoanionic CNC ligand 5 (bimca, l,8-bis(imidazolin-2-yliden-l-yl)carbazolide). Three equivalents of the base (lithium diisopropylamide (LDA), MeLi) are necessary to obtain the in situ formed Li(bimca) complex 23 (Scheme 9.2). Salt metathesis and ligand exchange with [Rh(CO)2(p-Cl)]2 afforded the Rh(CO)(bimca) complex 24 in good yields. 

While up to 1990 all attempts to isolate a stable N-heterocyclic carbene failed, metal complexes of unsaturated imidazol-2-ylidenes were known as early as 1968. The first complexes of this type were obtained by in situ deprotonation of imidazolium salts using mercury(ll) acetate or dimethylimidazolium hydridopentacarbonylchromate(-II) followed by coordination of the carbene to the metal center (Scheme 1.3). Shortly thereafter, the stabilization of the saturated imidazolin-2-ylidene in a metal complex was described by Lappert who treated electron-rich entetraamines of type 6=6 with coordinatively unsaturated transition metal complexes to obtain complexes with imidazolin-2-ylidene ligands (Scheme 1.3). ... 

Scheme 1.3 Synthesis of complexes with imidazol-2-ylidene and imidazolin-2-ylidene ligands.

V. I. Ovcharenko, S. V. Larionov, G. N. Mironova, and L. B. Volodarskii, Bull. Acad. Sci. USSR, Div. Chem. Sci., 1979,28, 599. Dimeric palladium(u) complexes with cyclometallated imidazoline nitrosyl radical ligands. 

Several chiral PCN pincer Pd(n) complexes with aryl-based aminophosphine-imidazolines have been reported by Gong and co-workers. The complexes were prepared by a two step synthetic strategy, starting from the corresponding aminophenyl-imidazoline derivatives which upon reaction with disubstituted chlorophosphines, yielded the aminophosphines 45a-c. Further complexation with PdClz gave the Pd(n) pincer complexes 46a-c (Scheme 10), which were characterized by elemental analysis and H, C, and P 1H NMR. 

Many derivatives of imidazoline nitroxides proved to be capable of chelation without involvement of the radical center. Complexes with ions of transition metals were generated from carboxylic acids 107 and 108... 

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