The bisimidazolium salt H_2-1(PF_6)_2 featuring a bridging 1,4-phenylene group reacts with 0.5 equiv of [PdCl(allyl)]_2 in the presence of Cs_2CO_3 to give the dinuclear complex [2](PF_6)_2, whereas the reaction of the same bisimidazolium salt with 0.5 equiv of [Ir(Cl)_2(Cp)] _2 yields the mononuclear orthometalated complex [3]PF_6 with one remaining imidazolium unit. The unreacted imidazolium group in complex [3]PF_6, however, can also be metalated with Rh~(III) to yield the doubly orthometalated heterobimetallic complex [4]. In complex [4], each M~(III) center (M = Ir~(III) and Rh~(III)) is coordinated by one NHC unit and orthometalates the central aryl ring of the ligand.
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