Inorganic Chemistry, Vol.55, No.12, 6018-6026, 2016
Asymmetric Synthesis of Enantiomerically Pure Mono- and Binuclear Bis(cyclometalated) Iridium(III) Complexes
Chiral precursors Lambda-[Ir(ppy)2(L-pro)] (Lambda-L, where ppy is 2-phenylpyridine; pro is proline), Lambda-[Ir(ppy)2(MeCN)(2)](PF6) (Delta-1), Delta-[Ir(ppy)(2)(D-pro)] (Delta-D), and A[Ir(ppy)(2)(MeCN)(2)] (PF6) (A-1) were synthesized from rac[(1r(ppy)(2))(2)Cl-2] and L-pro or D-pro by means of the auxiliary ligand strategy with 99% de values. The enantiopure mono complexes Lambda/Delta-[Ir(ppy)2(L)](PF6) (L is 2,2'-bipyridine, Lambda/Delta-2; L is 2,2'-dipyrimidine (dpm), A/A-3; L is 2,2'bibenzimidazole (H(2)bbim), Lambda/Delta-4) with 99% ee values and binuclear complexes Lambda Lambda/Delta Delta-[(Ir(ppy)(2))(2)(dpm)] (PF6)(2) (Lambda Lambda-5 and Delta Delta-5) and Lambda Lambda/Delta Delta-R1r(PPY)(2))(2)(bbim)] (Lambda Lambda-6 and Delta Delta-6) with 99% de values were synthesized in one step using the corresponding chiral precursors. The absolute configurations at Ir(III) centers of precursor A-1, mononuclear A-3, and binuclear AA-6 were confirmed by single-crystal structural analysis and characterized by circular dichroism (CD) spectroscopy. The correlation between the absolute configuration at Ir(III) center and CD spectra was established. The configurations at Ir(III) centers are stable during the reactions, and the chiral precursors can be used for the asymmetric synthesis of enantiomerically pure mono- and polynudear Ir(III) complexes. Moreover, meso Lambda Delta-[(Ir(ppy)(2))(2)(dpm)](PF6)(2) (meso-S) and Lambda Delta-[(Ir(ppy)(2))(2)(bbim)] (meso-6) were also synthesized using these precursors.