Homo- and heteronuclear complexes derived from <i>N</i>-picoline-functionalized benzimidazolin-2-ylidene ligands

Abstract The transformation of gold(I) complexes of the type [AuCl(NHC)] (NHC = N -picoline- N ′-R-functionalized benzimidazolin-2-ylidene ligand; R = Et, 1 ; R = n- Pr, 2 ; R = n- Bu, 3 ) into polynuclear complexes was studied. Chloride abstraction from [AuCl(NHC)] by treatment with silver tetrafluoroborate yielded the digold complexes [Au 2 ( 1 ) 2 ](BF 4 ) 2 –[Au 2 ( 3 ) 2 ](BF 4 ) 2 , featuring two gold atoms coordinated by an NHC carbon atom from one NHC ligand and a picoline nitrogen atom from the second NHC ligand each. Treatment of the gold complexes [AuCl(NHC)] (NHC = 1 − 3 ) with dicarbene silver complexes of type [Ag(NHC) 2 ][AgBr 2 ] (NHC = 1 − 3 ) in the presence of AgBF 4 proceeded under transmetalation of the NHC ligand to gold and formation of discrete heterodinuclear di-NHC complexes [AgAu( 1 ) 2 ](BF 4 ) 2 −[AgAu( 3 ) 2 ](BF 4 ) 2 , where the two NHC donors bind to the gold atoms, while the two pyridine donors bind to the silver atom. Reaction of the gold(I) complex [AuCl( 4 )] ( 4 = N , N ′-dipicoline-functionalized benzimidazolin-2-ylidene) with silver(I) complex [Ag( 4 ) 2 ][AgBr 2 ] in the presence of AgBF 4 yielded the trinuclear heterobimetallic complex [Ag 2 Au( 4 ) 2 ](BF 4 ) 3 featuring the gold atom coordinated by two carbene donors and the two silver atoms coordinated by the two pyridine donors from one ligand 4 . The molecular structures were determined for the homonuclear digold as well as for the heteronuclear Ag I /Au I and Ag I 2 /Au I complexes.