Cárdenas Diego J, Martín-Matute Belén, Echavarren Antonio M
Departamento de Química Organica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
J Am Chem Soc. 2006 Apr 19;128(15):5033-40. doi: 10.1021/ja056661j.
A computational study has been performed to determine the mechanism of the key steps of Pd-catalyzed domino reactions in which C(sp2)-C(sp2) are formed from aryl and alkenyl halides. DFT calculations were done on model complexes of the proposed intermediates, with PH3 and H2O as ancillary ligands, to explore two possible mechanisms: the oxidative addition of aryl or alkenyl halides to palladacycles to give Pd(IV) intermediates, and the transmetalation-type reaction of aryl or alkenyl ligands between two Pd(II) centers, a palladacycle, and a Pd(II) complex formed by oxidative addition of aryl or alkenyl halides to Pd0. We have shown that oxidative addition of iodoethylene to Pd0 precursors is more favorable than oxidative addition to Pd(II) palladacycles, whereas transmetalation-type reactions between Pd(II) complexes are facile. Similar results were obtained with iodobenzene instead of iodoethylene and formamide as the ancillary ligand. These results suggest that Pd(IV) intermediates are not involved in these reactions.
已开展一项计算研究，以确定钯催化多米诺反应关键步骤的机理，该反应中芳基卤化物和烯基卤化物形成C(sp2)-C(sp2)键。以PH3和H2O作为辅助配体，对所提出中间体的模型配合物进行了密度泛函理论（DFT）计算，以探究两种可能的机理：芳基或烯基卤化物向钯环进行氧化加成生成Pd(IV)中间体，以及芳基或烯基配体在两个Pd(II)中心、一个钯环和一个由芳基或烯基卤化物向Pd0进行氧化加成形成的Pd(II)配合物之间的转金属化型反应。我们已表明，碘乙烯向Pd0前体的氧化加成比向Pd(II)钯环的氧化加成更有利，而Pd(II)配合物之间的转金属化型反应很容易进行。用碘苯代替碘乙烯并以甲酰胺作为辅助配体时，也得到了类似结果。这些结果表明，这些反应中不涉及Pd(IV)中间体。
