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

Functional 2-pyrazolyl-6-phenylpyridine chelatesnamely, (pzpyph^Bu)­H₂ and (pzpyph^CF₃)­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] (<b>1a</b>), [Ir­(pzpyph^CF₃)­(PPh₂R)₂H] (<b>2a</b>–<b>2c</b>), 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] (<b>3a</b>) and [Ir­(pzpyph^Bu)­(dppe)­H] (<b>3b</b>), for which the distinctive, axial hydride undergoes rapid chlorination, forming chlorinated complexes [Ir­(pzpyph^Bu)­(dppb)­Cl] (<b>4a</b>) and [Ir­(pzpyph^Bu)­(dppe)­Cl] (<b>4b</b>), respectively. On the other hand, upon extensive heating of <b>2c</b>, one of its coordinated PPh₂(CH₂Ph) exhibits benzyl cyclometalation and hydride elimination to afford [Ir­(pzpyph^CF₃)­(PPh₂R)­(PPh₂R′)] (<b>5c</b> and <b>6c</b>) R = CH₂Ph and R′ = CH₂(<i>o</i>-C₆H₄) as the kinetic and thermodynamic products, respectively. Their structural, photophysical, and electrochemical properties are examined and further affirmed by the computational approaches