Mixed P-N and As-N Bis-Ylide Palladium Complexes: Cooperative Intramolecular Interactions, Conformational Preferences, and C-H Bond Activations
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- 作者：Elena Serrano ; Cristina Vallé ; s ; Jorge J. Carbó ; Agustí ; Lledó ; s ; Tatiana Soler ; Rafael Navarro ; Esteban P. Urriolabeitia
- 刊名：Organometallics
- 出版年：2006
- 出版时间：September 11, 2006
- 年：2006
- 卷：25
- 期：19
- 页码：4653 - 4664
- 全文大小：462K
- 年卷期：v.25,no.19(September 11, 2006)
- ISSN：1520-6041
文摘
The mixed ylide-pyridinium salts [Ph3P=C(H)C(O)CH2NC5H5]Cl (2a) and [Ph3As=C(H)C(O)CH2NC5H5]Br (15) have been prepared by reaction of the P and As ylides [Ph3P=C(H)C(O)CH2Cl] and[Ph3As=C(H)C(O)CH2Br] (14), respectively, with pyridine. These ylides react with Pd(II) salts in thepresence of bases, affording the four-membered C,C-chelated complexes cis-[PdCl2{
2-Ph3EC(H)C(O)C(H)NC5H5} (E = P (3), As (16)) as single diastereoisomers (meso form, RS/SR). Density functionaltheory (DFT) calculations revealed that the same conformational preferences are present in free mixedbis-ylides. We have established the presence of two cooperative intramolecular interactions of moderatestrength by means of Bader analysis of the electron density on model free bis-ylides: the 1,4-E···Ointeractions (E = P, As) and the 1,6-CH···O hydrogen bonds. The intramolecular 1,4-As···O interactionshave been fully characterized for the first time. These interactions play a key role in determining thepreferred conformations, which then are transferred to the complexes. Complex 3 reacts with AgClO4 togive the dinuclear species [Pd(
-Cl){2-Ph3PC(H)C(O)C(H)NC5H5}]2(ClO4)2 (4), which further reactswith L ligands to give [PdCl{2-Ph3PC(H)C(O)C(H)NC5H5}L](ClO4) (L = PPh3 (6), PPhMe2 (7)) assingle geometric isomers. The molecular structure of 6 has been determined by X-ray diffraction methods.Complex 6 evolves in refluxing NCMe to give the ortho-metalated derivative [PdCl(C6H4-2-PPh2C(H)C(O)CH2NC5H5)(PPh3)]ClO4 (18). In addition, ylide 2a reacts with PtCl2 in refluxing2-methoxyethanol to give the ortho-platinated complex [Pt(-Cl)(C6H4-2-PPh2C(H)C(O)CH2NC5H5)](Cl)2(20). The role of the electronic and steric factors in the cleavage of the halide bridging system in 4 andin the ortho-metalation reactions affording 18 and 20 is also discussed.
2-Ph3EC(H)C(O)C(H)NC5H5} (E = P (3), As (16)) as single diastereoisomers (meso form, RS/SR). Density functionaltheory (DFT) calculations revealed that the same conformational preferences are present in free mixedbis-ylides. We have established the presence of two cooperative intramolecular interactions of moderatestrength by means of Bader analysis of the electron density on model free bis-ylides: the 1,4-E···Ointeractions (E = P, As) and the 1,6-CH···O hydrogen bonds. The intramolecular 1,4-As···O interactionshave been fully characterized for the first time. These interactions play a key role in determining thepreferred conformations, which then are transferred to the complexes. Complex 3 reacts with AgClO4 togive the dinuclear species [Pd(-Cl){2-Ph3PC(H)C(O)C(H)NC5H5}]2(ClO4)2 (4), which further reactswith L ligands to give [PdCl{2-Ph3PC(H)C(O)C(H)NC5H5}L](ClO4) (L = PPh3 (6), PPhMe2 (7)) assingle geometric isomers. The molecular structure of 6 has been determined by X-ray diffraction methods.Complex 6 evolves in refluxing NCMe to give the ortho-metalated derivative [PdCl(C6H4-2-PPh2C(H)C(O)CH2NC5H5)(PPh3)]ClO4 (18). In addition, ylide 2a reacts with PtCl2 in refluxing2-methoxyethanol to give the ortho-platinated complex [Pt(-Cl)(C6H4-2-PPh2C(H)C(O)CH2NC5H5)](Cl)2(20). The role of the electronic and steric factors in the cleavage of the halide bridging system in 4 andin the ortho-metalation reactions affording 18 and 20 is also discussed.