Syntheses and characterizations of thiolato-functionalized N-heterocyclic carbene Pd(ii) complexes with normal and mesoionic binding modes

Abstract

The thiolato-bridged dimeric Pd(II) NHC complex 1 has been synthesized from the reaction of thioester-functionalized imidazolium salt B and Pd(OAc)₂. The isolation of its interesting constitutional isomer 2 bearing both classical C(2)-bound and mesoionic C(4)-bound ligands coordinating to two different metal centers in the same complex allowed for a direct comparison of these isomeric carbenes. Reactivity studies of 1 with NaSCH(CH₃)₂ and NaBF₄ afforded the tetranuclear compound 3 with a [Pd₄S₄] macrocycle. All complexes have been fully characterized by multinuclei NMR spectroscopies, ESI mass spectrometry and X-ray diffraction analysis.