Intramolecular Transmetalation of Arylpalladium(II) and Arylplatinum(II) Complexes with Silanes and Stannanes

The oxidative addition of o -(Me 2 RSiCH 2 O)C 6 H 4 I (R = Me, Ph, F) to palladium(0) complexes [Pd(PPh 3 )], [Pd(dba)(AsPh 3 ) 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 -(Me 2 RCH 2 O)C 6 H 4 Pd(L 2 )I (L = PPh 3, AsPh 3; 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(PPh 3 )] 4 was shown to behave as a moderate catalyst for the cross-coupling of two aryl triflates with ethenyltributylstannane to form the corresponding styrenes.