科研之友
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摘要
The synthesis of three azoderivatives {R-1-N=N-R-2 with R-1 = 2-phenylindole and R-2 = 4-Me-C6H4-(2a), 4-Cl-C6H4-(2b) or 2-phenylindole (2c)} and the study of their reactivity in front of Pd(II) salts are described. Treatment of 2a or 2b with PdCl2 in a CH2Cl2:CH3OH mixture at 298 K followed by the action of PPh3 produced the cyclopalladated complexes: [Pd(kappa(2)-C,N)Cl(PPh3)] (3a and 3b) with a sigma{Pd -C(indole)} bond. For 2c, metallation takes place on the same position but required stronger reaction conditions {Pd(OAc)2 in acetic acid at 398 K}. A comparative study of the spectroscopic and photo-optical properties of ligands 2a-2c and their palladium(II) derivatives (3a-3c) is also reported. Addition of PPh3 to CH2Cl2 solutions of compounds 3a-3c produced the opening of the six-membered metallacycle and the formation of the trans-[Pd(kappa(1)-N)Cl(PPh3)(2)] derivatives (4a-4c). The crystal structures of 3c center dot CH2Cl2, 4a, 4b and 4c center dot 3/2CH(2)Cl(2)center dot 1/2H(2)O confirm the mode of binding and the anti-(E) configuration of 2a-2c in the complexes as well as the relative disposition of the remaining ligands bound to the Pd(II) atom. Solution studies reveal that in CDCl3, the Pd-N bond of 4a-4c is hemilabile. Computational studies (at DFT or PM6 level) have also been performed in order to rationalize the high degree of regioselectivity of the cyclopalladation process and the solution behaviour of 4a-4c.
- 出版日期2013-2-15
