Stepwise Formation of Iridium(III) Complexes with Monocyclometalating and Dicyclometalating Phosphorus Chelates

With the motivation of assembling cyclometalated complexes without nitrogen-containing heterocycle, we report here the design and systematic synthesis of a class of Ir(III) metal complexes functionalized with facially coordinated phosphite (or phosphonite) dicyclometalate tripod, together with a variety of phosphine, chelating diphosphine, or even monocyclometalate phosphite ancillaries. Thus, treatment of [IrCl3(tht)3] with stoichiometric amount of triphenylphosphite (or diphenyl phenylphosphonite), two equiv of PPh3, and in presence of NaOAc as cyclometalation promoter, gives formation of respective tripodal dicyclometalating complexes [Ir(tpit)(PPh3)2Cl] (2a), [Ir(dppit)(PPh3)2Cl] (2b), and [Ir(dppit)(PMe2Ph)2Cl] (2c) in high yields, where tpitH2 = triphenylphosphite and dppitH2 = diphenyl phenylphosphonite. The reaction sequence that afforded these complexes is established. Of particular interest is isolation of an intermediate [Ir(tpitH)(PPh3)2Cl2] (1a) with monocyclometalated phosphite, together wit...