Benzodicarbene-bridged dinuclear complexes as building blocks for metalosupramolecular architectures

Dinuclear benzodicarbene-bridged iridium(III) and rhodium(III) complexes [Cp*(Cl)2M(benzodicarbene)M(Cl)2Cp*] [3]–[5] have been synthesized from N,N′,N″,N″-tetraalkylbenzobisimidazolium salts and [MCp*(Cl)2]2 via the Ag2O method. Molecular structure determinations show an anti-arrangement of the {MCp*} moieties relative to the bridging dicarbene ligand. Complexes [3]−[5] have been dehalogenated once at each metal atom which led to the formation of tetranuclear rectangles [7](BF4)4–[9](BF4)4 featuring two benzodicarbene and two dichloro bridges between the metal centers. Removal of all halogen atoms from complexes [3] and [4] with AgBF4 in acetonitrile yielded dinuclear iridium(III) and rhodium(III) complexes of type [Cp*(MeCN)2M(benzodicarbene)M(MeCN)2Cp*](BF4)2 [10](BF4)4–[11](BF4)4.