کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1326289 977422 2009 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Palladium complexes of bis(acyclic diaminocarbene) ligands with chiral N-substituents and 8-membered chelate rings
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی معدنی
پیش نمایش صفحه اول مقاله
Palladium complexes of bis(acyclic diaminocarbene) ligands with chiral N-substituents and 8-membered chelate rings
چکیده انگلیسی

Reaction of cis-dichloridobis(p-trifluoromethylphenylisocyanide)palladium(II) with N,N′-bis[(R)-1-phenylethyl]-1,3-diaminopropane afforded an enantiomerically pure, C1-symmetric bis(acyclic diaminocarbene)PdCl2 complex in 41% yield. The X-ray crystal structure of the complex revealed that three of the four carbene nitrogens are twisted out of conjugation with the carbene units, apparently as a result of steric interactions between one phenyl group and the propylene backbone of the chelate. A similar reaction with N,N′-bis[(R)-1-(1-naphthyl)ethyl]-1,3-diaminopropane did not lead to an isolable bis(carbene) complex, instead forming significant amounts of bis(ammonium) salt as a decomposition product. However, reaction of the same palladium isocyanide precursor with a mixture of all diastereomers of N,N′-bis[1-(1-naphthyl)ethyl]-1,3-diaminopropane provided an achiral, Cs-symmetric palladium bis(acyclic diaminocarbene) complex derived exclusively from the (R,S) diamine in 20% yield. An X-ray structure showed that the (R,S) stereochemistry allows the bulky naphthyl groups to adopt an orientation that avoids steric interactions with the backbone that likely lead to the instability of the homochiral analogue. The two palladium carbene complexes catalyzed the aza-Claisen rearrangement of an allylic imidate to an allylic amide in 24–34% yield, with an enantiomeric excess of 8% ee for the [(R)-1-phenylethyl]-substituted complex.

Reaction of a palladium bis(isocyanide) complex with a diamine bearing (R)-1-phenylethyl N-substituents affords a chiral, C1-symmetric, bis(acyclic diaminocarbene) chelate complex in one step. Increased bulk on the amine disfavors homochiral bis(ADC) ligands, though an achiral analogue was isolable.Figure optionsDownload as PowerPoint slide

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Organometallic Chemistry - Volume 694, Issue 20, 15 September 2009, Pages 3297–3305
نویسندگان
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