Intermolecular Alkynyl Ligand Transfer in Palladium(II) and Platinum(II) Complexes with −C⋮CCOOR and −C⋮CPh Ligands. Relative Stability of the Alkynyl Complexes and Conproportionation of Dialkynyl and Diiodo Complexes of These Metals

An equimolar reaction of trans -Pd(C⋮CCOOMe) 2 (PEt 3 ) 2 with trans -PdI 2 (PEt 3 ) 2 catalyzed by CuI causes conproportionation of the complexes at room temperature, producing trans -PdI(C⋮COOMe)(PEt 3 ) 2 in 88% yield, while the reaction without CuI catalyst gives the monoalkynylpalladium complex in approximately 2% yield after a prolonged period. Similar reactions of trans -Pd(C⋮CPh) 2 (PEt 3 ) 2 with trans -PdI 2 (PEt 3 ) 2 with and without CuI catalyst give the alkynyl ligand transfer reaction product trans -PdI(C⋮CPh)(PEt 3 ) 2 in 95% and 33% yields, respectively. CuI-catalyzed conproportionation of trans -Pt(C⋮CPh) 2 (PEt 3 ) 2 and trans -PtI 2 (PEt 3 ) 2 occurs more slowly than the corresponding reactions of the Pd complexes; trans -Pt(C⋮CCOOMe) 2 (PEt 3 ) 2 does not react with the diiodoplatinum complex even in the presence of CuI. The alkynyl ligand transfer reaction from trans -Pd(C⋮CCOOMe) 2 (PEt 3 ) 2 to trans -PtI 2 (PEt 3 ) 2 occurs in the presence of CuI catalyst, affording a mixture of several organopalladium and -platinum complexes. The main Pd complex in the reaction mixture is trans -PdI(C⋮CCOOMe)(PEt 3 ) 2, while the Pt-containing product is composed of trans -Pt (C⋮CCOOMe) 2 (PEt 3 ) 2, trans -PtI(C⋮CCOOMe)(PEt 3 ) 2, and trans -PtI 2 (PEt 3 ) 2 in an approximate 1:2:1 molar ratio. Mixing of trans -Pd(C⋮CCOOMe) 2 (PEt 3 ) 2, trans -PdI 2 (PEt 3 ) 2, and trans -PtI 2 (PEt 3 ) 2 results in the formation of trans -PdI(C⋮CCOOMe)(PEt 3 ) 2 in a high yield, while the alkynyl ligand transfer from Pd to Pt complexes is almost negligible. trans -PtI 2 (PEt 3 ) 2 catalyzes the alkynyl ligand transfer between the dialkynyl- and diiodopalladium(II) complexes and remains unchanged in the reaction mixture.