Ring-expansion and solvation of cyclodimeric Pd(II) complex

The reaction of (COD)PdCl2 (COD = 1,5-cyclooctadiene) in ethanol with 1,7-bis(4-pyridyl)octamethyltetrasiloxane (p-poms) in acetone at room temperature affords single crystals consisting of cyclodimers, [PdCl2(p-poms)]2, whereas the reaction in the solvents at boiling temperature yields amorphous solid of cyclotrimers, [PdCl2(p-poms)]3. The cyclodimers are completely converted to the cyclotrimers in a boiling chloroform solution. In contrast, the cyclotrimers are partly returned to the cyclodimers in chloroform in the 10-60 °C range. Furthermore, the cyclodimers are retained in dimethyl sulfoxide (Me2SO), but sonication of the Me2SO solution results in the stepwise transformation to the cyclotrimers of stepwise Me2SO-adducts, [Pd3Cl5(Me2SO)(p-poms)3]·Cl and [PdCl(Me2SO)(p-poms)]3·Cl3 and further the sonication at 60 °C finally yields [Pd(Me2SO)2(p-poms)]3·Cl6.