Room temperature transmetallation from tris(pentafluorophenyl)borane to cyclometallated iridium(iii)

Abstract

Transmetallation reactions involving organoboron reagents and transition metals are legion in synthetic organometallic chemistry and homogeneous catalysis. Triarylboranes (BAr₃) have been observed to participate in transmetallation reactions with many transition metals, typically following abstraction of an alkyl (R⁻) or hydride ligand by the Lewis acidic borane. Here, an unusual transmetallation strategy is described where an aryl group from a borane replaces a weakly coordinated PF₆⁻ ligand. The precursors Ir(C^N)₂(CNAr)(FPF₅) (C^N = cyclometallating ligand, CNAr = aryl isocyanide) react smoothly with B(C₆F₅)₃ to give complexes of the type Ir(C^N)₂(CNAr)(C₆F₅), a previously unobserved structure type featuring an unchelated aryl ligand. The reaction tolerates a variety of C^N ligands and a range of electronically and sterically varied aryl isocyanide ancillary ligands. A total of six complexes of this type are described, two of which are characterized by single-crystal X-ray diffraction. All but one of the complexes luminesces at room temperature, with the emission wavelength dependent on the C^N ligand.