摘要:
Vinyl chloride (VC) reacts with the cationic Pd complexes [L2Pd(Me)(CO)] [B(C6F5)(4)] (3a-d; L-2 = Me(2)bipy, (t)Bu(2)bipy, dppp, dmpe) and [L2Pd{C(=O)Mej(CO)] [B(C6F5)(4)] (4a-d) by 2,1-insertion of L2Pd{C=O)Me}(VC)(+) intermediates to yield the O-chelated products [L2Pd-CHClCH2C(=O)Me}[B(C6F5)(4)] (5a-d). 5a-d were characterized by NMR spectroscopy, and the molecular structures of 5a and 5b.CH2Cl2 were determined by X-ray crystallography. The VC 2,1-insertion regiochemistry is favored in part because the alternative L2Pd{CH2CHClC(=O)Me}(+) 1,2-insertion products would be destabilized by placement of the electron-withdrawing Cl and acyl substituents on the same carbon. In contrast to analogous nonhalogenated L2Pd{CHRCHR'C(=O)Me}(+) species, 5a,c do not further react with CO, due to the stability of the chelate ring and the low migratory aptitude of the -CHClCH2C(=O)Me group.