Iridium(III) Complexes Bearing Tridentate Chromophoric Chelate: Phosphorescence Fine-Tuned by Phosphine and Hydride...

Functional 2-pyrazolyl-6-phenylpyridine chelates-namely, (pzpyph^Bu)H₂ and (pzpyph^CF)H₂ and phosphines-are successfully employed in the preparation of emissive Ir(III) metal complexes, for which the reaction with phosphine such as PPh₃, PPh₂Me, and PPh₂(CH₂Ph) afford corresponding Ir(III) complexes [Ir(pzpyph^Bu)(PPh₃)₂H] (1a), [Ir(pzpyph^CF)(PPh₂R)₂H] (2a-2c), R = Ph, Me, CH₂Ph, which also show an equatorial coordinated hydride. In contrast, treatment with 1,2-bis(diphenylphosphino)benzene (dppb) and 1,2-bis(diphenylphosphino)ethane (dppe) yields the isomeric products [Ir(pzpyph^Bu)(dppb)H] (3a) and [Ir(pzpyph^Bu)(dppe)H] (3b), for which the distinctive, axial hydride undergoes rapid chlorination, forming chlorinated complexes [Ir(pzpyph^Bu)(dppb)Cl] (4a) and [Ir(pzpyph^Bu)(dppe)Cl] (4b), respectively. On the other hand, upon extensive heating of 2c, one of its coordinated PPh₂(CH₂Ph) exhibits benzyl cyclometalation and hydride elimination to afford [Ir(pzpyph^CF)(PPh₂R)(PPh₂R')] (5c and 6c) R = CH₂Ph and R' = CH₂( o-C₆H₄) as the kinetic and thermodynamic products, respectively. Their structural, photophysical, and electrochemical properties are examined and further affirmed by the computational approaches.