Cis/trans equilibrium as the way to form Pd carbene catalyst from trans-isocyanide complex

Abstract

The behavior of Pd(II) bis-isocyanide complexes in solution was studied for examples of bis-(cyclohexylisocyanide)palladium(II) dichloride (1) and diiodide (2). The equilibrium between isomeric cis- and trans-forms of 1 was observed by NMR and IR spectroscopy. Complex 1 (which has the cis-configuration in the solid state) gives cis-/trans-isomeric mixture after dissolving in CDCl₃ for several days at room temperature. The effect of heating on the equilibration rate was considered. The studied equilibrium leads to a purely cis-structure of Pd carbene complex (3) that was synthesized via the interaction of cis-/trans-isomeric mixture of 1 with benzophenone hydrazone.

Keywords:

• Pd(II) Isocyanide complexes
• Acyclic diaminocarbenes
• Cis/trans equilibrium
• Cross-coupling catalysts

Notes

^† The experimental points measured during the first two minutes of the experiment are ignored. This is due to the time needed for the complete heating of the sample in the NMR tube.