Intermolecular transfer of organic ligands among transition metal complexes

Transmetalation is one of the important fundamental reactions which constitute of synthetic organic reactions such as homo-and cross-coupling and alkene polymerization。This study aimed elucidation of detailed mechanism of transmetalation of organotransition metal complexes。Arylpalladium alkynyl complexes with tertiary phosphime ligands react with arylpalladium iodo complexes below room temperature to cause intermoelcular alkynyl ligand transfer to give new organopalladium complexes.Alkynyl-palladium bond is thermodynamically more stable than the aryl-palladium bond but much more reactive because the transmetalation of the alkynyl ligand is favored by high stability of intermediate dinuclear complexes with bridging alkynyl ligand.Similar alkynyl ligand transfer from Pd to Pt complexes requires higher termperature or addition of CuI catalyst.Dialkynylpalladium and platinum complexes react with diiodo complexes of these metals to cause the complexes via transmetalation of the alkynyl ligands.Distribution of the product is influenced by thermodynamic stability of the complexes and the presence or absence of CuI catalyst which enhances the reaction significantly.Arylpalladium iodo complexes with chelating diamines do not cause intermolecular aryl ligand transfer，whereas the cationic species prepared from addition of AgBF I D24I D2 to the complexes undergo proportionation to give diarylpalladium complexes.The product give biaryl via reductive elimination，which is related to the mechanism of homocoupling reaction catalyzed by group10 metal complexes.Rates of the transmetalation depend highly on kinds of aryl group；the complexes with fluorinated aryl ligand exhibit low reactivity toward the transmetalation.In summary，the present study has revealed various aspects of transmetalation of organotransition metal complexes and elucidated the mechanism of several synthetic organic reactions that involve transmetalation as a crucial step。

Transmetalation is one of the important fundamental reactions which constitute of synthetic organic reactions such as homo- and cross-coupling and alkene polymerization. This study aimed elucidation of detailed mechanism of transmetalation of organotransition metal complexes. Arylpalladium alkynyl complexes with tertiary phosphime ligands react with arylpalladium iodo complexes below room temperature to cause intermoelcular alkynyl ligand transfer to give new organopalladium complexes. Alkynyl-palladium bond is thermodynamically more stable than the aryl-palladium bond but much more reactive because the transmetalation of the alkynyl ligand is favored by high stability of intermediate dinuclear complexes with bridging alkynyl ligand. Similar alkynyl ligand transfer from Pd to Pt complexes requires higher termperature or addition of CuI catalyst.Dialkynylpalladium and platinum complexes react with diiodo complexes of these metals to cause the complexes via transmetalation of the alkynyl ligands. Distribution of the product is influenced by thermodynamic stability of the complexes and the presence or absence of CuI catalyst which enhances the reaction significantly.Arylpalladium iodo complexes with chelating diamines do not cause intermolecular aryl ligand transfer, whereas the cationic species prepared from addition of AgBFィイD24ィエD2 to the complexes undergo disproportionation to give diarylpalladium complexes. The product give biaryl via reductive elimination, which is related to the mechanism of homocoupling reaction catalyzed by group 10 metal complexes. Rates of the transmetalation depend highly on kinds of aryl group; the complexes with fluorinated aryl ligand exhibit low reactivity toward the transmetalation.In summary, the present study has revealed various aspects of transmetalation of organotransition metal complexes and elucidated the mechanism of several synthetic organic reactions that involve transmetalation as a crucial step.