Synthesis and Characterization of PdII Complexes with Bis-Pyridinium and Isoquinolinium N-Ylides: Moderate C-H···O=C Intramolecular Hydrogen Bonds as Source of Conformational
详细信息 查看全文
- 作者：Agustí ; Lledó ; s ; Jorge J. Carbó ; Rafael Navarro ; Elena Serrano ; and Esteban P. Urriolabeitia
- 刊名：Inorganic Chemistry
- 出版年：2004
- 出版时间：November 29, 2004
- 年：2004
- 卷：43
- 期：24
- 页码：7622 - 7635
- 全文大小：319K
- 年卷期：v.43,no.24(November 29, 2004)
- ISSN：1520-510X
文摘
The bis(N-ylide) PdII complexes cis-[PdX2{
2-[C(H)NCxHy]2CO}] (X = I, NCxHy = NC5H5, 2a; X = Br, NCxHy =NC5H5 and NC5H3-2,3-Me2, 2c, isoquinolinium NC9H7, 2d) have been prepared by reaction of the correspondingbis-pyridinium salts with Pd(OAc)2 (1:1 molar ratio). Compounds 2 react with AgClO4 and Tl(acac) (1:1:1 molarratio) to give the acetylacetonato derivatives [Pd(acac-O,O'){2-[C(H)NCxHy]2CO}]ClO4 (3a, c, d). In compounds2 and 3, the bis-ylide is bonded as a C,C-chelate ligand through the two ylidic C
atoms. The reaction isstereoselective, and only one diastereoisomer is observed (meso form, RS/SR). The origin of the observedstereoselectivity lies with the establishment of intramolecular C-H···O=C hydrogen bonds between the orthoprotons of the pyridine or isoquinoline fragments and the carbonyl oxygen, as it has been shown by density functionaltheory (DFT) calculations (B3LYP level) and Bader analysis of the electron density on model pyridinium ylides.Despite the inherent weakness of the C-H···O=C bonds, the results show that in these N-ylides the hydrogenbonds are stronger than expected and should be classified as moderate H bonds.
2-[C(H)NCxHy]2CO}] (X = I, NCxHy = NC5H5, 2a; X = Br, NCxHy =NC5H5 and NC5H3-2,3-Me2, 2c, isoquinolinium NC9H7, 2d) have been prepared by reaction of the correspondingbis-pyridinium salts with Pd(OAc)2 (1:1 molar ratio). Compounds 2 react with AgClO4 and Tl(acac) (1:1:1 molarratio) to give the acetylacetonato derivatives [Pd(acac-O,O'){2-[C(H)NCxHy]2CO}]ClO4 (3a, c, d). In compounds2 and 3, the bis-ylide is bonded as a C,C-chelate ligand through the two ylidic C atoms. The reaction isstereoselective, and only one diastereoisomer is observed (meso form, RS/SR). The origin of the observedstereoselectivity lies with the establishment of intramolecular C-H···O=C hydrogen bonds between the orthoprotons of the pyridine or isoquinoline fragments and the carbonyl oxygen, as it has been shown by density functionaltheory (DFT) calculations (B3LYP level) and Bader analysis of the electron density on model pyridinium ylides.Despite the inherent weakness of the C-H···O=C bonds, the results show that in these N-ylides the hydrogenbonds are stronger than expected and should be classified as moderate H bonds.