Platinum Complexes with Picoline-functionalized Benzimidazolin-2-ylidene Ligands

The dicarbene platinum complexes of the type [Pt(L)2]Br2 [5]Br2 – [8]Br2 (L = N-alkyl-N′picolylbenzimidazolin-2-ylidene) have been prepared by two different methods. The in situ deprotonation of picoline-functionalized benzimidazolium salts 1 – 4 with platinum acetylacetonate gave the platinum complexes [5]Br2 – [8]Br2 in good yields. Complex [8]Br2 has also been obtained by a ligand transfer reaction from the silver dicarbene complex [9][AgBr2]. Attempts to cystallize [8]Br2 obtained from the carbene transfer reaction led to the isolation of the previously undetected monocarbene complex [Pt(Cl)2L] (10) which contains only one picoline-functionalized carbene ligand coordinating in a chelating fashion to the metal center.