Intramolecular transmetalation of arylpalladium(II) and arylplatinum(II) complexes with silanes and stannanes

The oxidative addition of o-(Me2RSiCH2C))C6H4I (R = Me, Ph, Fl to palladium(0) complexes [Pd(PPh3)], [Pd(dba)(AsPh3)(2)] (dba = dibenzylideneacetone), and [Pd(dba)(L-2)] [L-2 = 1,1'-bis(diphenylphosphino)ferrocene (dppf), 2,2'-bipyridine (bpy), o-phenanthroline (phen)] leads to the corresponding complexes o-(Me2RCH2O)C6H4Pd(L-2)I (L = PPh3, AsPh3; L-2 = dppf, bpy, phen). This Pd(II)/Si transmetalation, the key step in the Hiyama cross-coupling reaction, proceeds smoothly with different; fluorides as the promoters. Additionally, silver and potassium carbonate promote the transmetalation by the likely formation of an intermediate with a Pd-O bond. The related Pt(II)/Sn and Pt(II)/Si transmetalation leads to the formation of stable oxaplatinacycles. In contrast with the requirement of additives for the Pd(II)/Si transmetalation, the transmetalation of Pt(II) complexes proceeds directly in the absence of additives. Additionally, [Pt(PPh3)](4) was shown to behave as a moderate catalyst for the cross-coupling of two aryl triflates with ethenyltributylstannane to form the corresponding styrenes.