Insertion of Substituted Alkynes into the Pd-C Bond of Methyl and Vinyl Palladium(II) Complexes Bearing Pyridylthioethers as Ancillary Ligands. The Influence of Ligand Substituents at Pyridine and Sul
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- 作者：Luciano Canovese ; Fabiano Visentin ; Gavino Chessa ; Paolo Uguagliati ; Claudio Santo ; and Alessandro Dolmella
- 刊名：Organometallics
- 出版年：2005
- 出版时间：June 20, 2005
- 年：2005
- 卷：24
- 期：13
- 页码：3297 - 3308
- 全文大小：209K
- 年卷期：v.24,no.13(June 20, 2005)
- ISSN：1520-6041
文摘
The palladium(II) chloro methyl complexes bearing the bidentate 6-R-C5H3N-2-CH2SR'(RN-SR'; R = H, Me, Cl; R' = Me, t-Bu, Ph) and the potentially terdentate 2,6-(CH2SR')2-C5H3N (S-N-S(R'); R' = Me, t-Bu, Ph) pyridylthioethers as ancillary ligands were synthesized,characterized, and reacted with substituted alkynes ZC
CZ (Z = COOMe, Z' = COOt-Bu,Z' ' = COOEt). The reactions were followed under second-order conditions by 1H NMRtechnique, and the reaction rates were determined. The corresponding vinyl derivatives weresynthesized, and in the case of the complexes [PdCl(ZC=CZMe)(MeN-SPh)] and [PdCl(ZC=CZMe)(C1N-St-Bu)] (Z = COOMe) reaction rates for alkyne insertion yielding the corresponding butadienyl complexes were also determined. The rate of insertion of the secondalkyne on the vinyl complex is more than 3 orders of magnitude lower than the first insertionrate in both the studied complexes, thereby allowing easy separation between vinyl andbutadienyl derivatives and an easy preparation of mixed butadienyl esters. Furthermore,the reaction rates are strongly dependent on the steric and electronic features of the ancillaryligands. In particular, the distortion of the complex main coordination plane, induced bythe substituent in position 6 of the pyridine ring, was found to significantly influence thesubstrate reactivity. The structures of the mono-inserted vinyl [PdCl(ZC=CZMe)(MeN-St-Bu)] (1) and the bis-inserted butadienyl [PdCl((ZC=CZ)2Me)(MeN-St-Bu)] (2) complexes weredetermined by X-ray diffraction, and the persistence of a structural distortion of the complexskeleton was observed. Moreover, the distortion may be related to facile ancillary liganddisplacement, a feature that can be exploited for the synthesis of substrates that would notbe easily obtained otherwise.
CZ (Z = COOMe, Z' = COOt-Bu,Z' ' = COOEt). The reactions were followed under second-order conditions by 1H NMRtechnique, and the reaction rates were determined. The corresponding vinyl derivatives weresynthesized, and in the case of the complexes [PdCl(ZC=CZMe)(MeN-SPh)] and [PdCl(ZC=CZMe)(C1N-St-Bu)] (Z = COOMe) reaction rates for alkyne insertion yielding the corresponding butadienyl complexes were also determined. The rate of insertion of the secondalkyne on the vinyl complex is more than 3 orders of magnitude lower than the first insertionrate in both the studied complexes, thereby allowing easy separation between vinyl andbutadienyl derivatives and an easy preparation of mixed butadienyl esters. Furthermore,the reaction rates are strongly dependent on the steric and electronic features of the ancillaryligands. In particular, the distortion of the complex main coordination plane, induced bythe substituent in position 6 of the pyridine ring, was found to significantly influence thesubstrate reactivity. The structures of the mono-inserted vinyl [PdCl(ZC=CZMe)(MeN-St-Bu)] (1) and the bis-inserted butadienyl [PdCl((ZC=CZ)2Me)(MeN-St-Bu)] (2) complexes weredetermined by X-ray diffraction, and the persistence of a structural distortion of the complexskeleton was observed. Moreover, the distortion may be related to facile ancillary liganddisplacement, a feature that can be exploited for the synthesis of substrates that would notbe easily obtained otherwise.