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

Abstract

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 [IrCl(3)(tht)(3)] with stoichiometric amount of triphenylphosphite (or diphenyl phenylphosphonite), two equiv of PPh(3), and in presence of NaOAc as cyclometalation promoter, gives formation of respective tripodal dicyclometalating complexes [Ir(tpit)(PPh(3))(2)Cl] (2a), [Ir(dppit)(PPh(3))(2)Cl] (2b), and [Ir(dppit)(PMe(2)Ph)(2)Cl] (2c) in high yields, where tpitH(2) = triphenylphosphite and dppitH(2) = diphenyl phenylphosphonite. The reaction sequence that afforded these complexes is established. Of particular interest is isolation of an intermediate [Ir(tpitH)(PPh(3))(2)Cl(2)] (1a) with monocyclometalated phosphite, together with the formation of [Ir(tpit)(tpitH)(PPh(3))] (3a) with all tripodal, bidentate, and monodentate phosphorus donors coexisting on the coordination sphere, upon treatment of 2a with a second equiv of triphenylphosphite. Spectroscopic studies were performed to explore the photophysical properties. For all titled Ir(III) complexes, virtually no emission can be observed in either solution at room temperature or 77 K CH(2)Cl(2) matrix. Time-dependent DFT calculation indicates that the lowest energy triplet manifold involves substantial amount of metal centered (3)MC dd contribution. Due to its repulsive potential energy surface (PES) that touches the PES of ground state, the (3)MC dd state executes predominant nonradiative deactivation process.

Origins of Regioselectivity in Iridium Catalyzed Allylic Substitution

“…Cyclometalated allyliridium triphenylphosphite complexes have been proposed as intermediates in allylic substitution reactions catalyzed by iridium triphenylphosphite complexes . Although cyclometalated iridium triphenylphosphite complexes have been isolated previously, − they have not been evaluated as potential intermediates in iridium catalyzed allylic substitution reactions. We performed a series of catalytic and stoichiometric reactions to assess the competence of allyliridium complexes 3a and 3b to be intermediates in iridium catalyzed allylic substitution reactions.…”

Bis‐Tridentate Iridium(III) Phosphors with Very High Photostability and Fabrication of Blue‐Emitting OLEDs

“…They were synthesized in a one‐pot manner, i.e., heating of a 1:1:1 mixture of IrCl 3 ·3H 2 O, carbene pincer pro‐chelate, pzyph chelate, and excess of potassium acetate in propionic acid 18. The added metal acetate works as a cyclometalation promoter via a sequence of concerted metalation and deprotonation reaction 19. Representative sky‐blue and blue‐emitting Ir(III) complexes [Ir(mimf)(pzyph F )] ( SB ) and [Ir(mimb)(pzy tB Oh F )] ( Px‐5 ) were obtained (cf.…”

Mechanistic Investigation of Improved Syntheses of Iridium(III)-Based OLED Phosphors

“…In an attempt to study the associated reaction sequences, i.e. phosphine addition versus cyclometalation, we then conducted the reaction of [Ir(tht) 3 Cl 3 ] with 3 equiv of bdpH in the absence of NaOAc with the hope of synthesizing the substitution products at different stages . To our surprise, only the Ir(III) complex [Ir(bdp)(bdpH)(tht)Cl 2 ] ( 8 ), which contains one coordinated bdpH, together with one cyclometalated bdp chelate, was isolated in lower yield (≤24%).…”