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 (BAr) 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 PF ligand. The precursors Ir(C^N)(CNAr)(FPF) (C^N = cyclometallating ligand, CNAr = aryl isocyanide) react smoothly with B(CF) to give complexes of the type Ir(C^N)(CNAr)(CF), 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.

Facile Synthesis of Luminescent Ir–Pt–Ir Trimetallic Complexes

“…General procedure for preparation of 1 b and 1 c : The complexes 1 b and 1 c were synthesized following the previously published method for 1 a by treating the Ir dimer [Ir(C^N) 2 (μ‐Cl)] 2 with 2,6‐dimethylphenyl isocyanide in CH 2 Cl 2 inside the glove box …”

“…The syntheses startw ith the complexes [Ir(C^N) 2 (CNAr dmp )Cl],w hich are easily prepared by treatingt he dimers [Ir(C^N)(m-Cl)] 2 with two equivalents CNAr dmp at room temperature;t he complex [Ir(F 2 ppy) 2 (CNAr dmp )Cl] (1a)w as reported previously and other related complexes have been prepared via an analogous route. [51,54] Our group has previously shown that am ore reactive Ir precursor [Ir(C^N) 2 (CNAr)(FPF 5 )] can be prepared by treating [Ir(C^N) 2 (CNAr)Cl] complexesw ith one equivalento f AgPF 6 ,r eplacing the chloride anion with aw eakly coordinated k 1 -PF 6 À anion. [51] In this way,t he [Ir(F 2 ppy) 2 (CNAr dmp )(FPF 5 )] precursor was prepared.…”

“…[51,54] Our group has previously shown that am ore reactive Ir precursor [Ir(C^N) 2 (CNAr)(FPF 5 )] can be prepared by treating [Ir(C^N) 2 (CNAr)Cl] complexesw ith one equivalento f AgPF 6 ,r eplacing the chloride anion with aw eakly coordinated k 1 -PF 6 À anion. [51] In this way,t he [Ir(F 2 ppy) 2 (CNAr dmp )(FPF 5 )] precursor was prepared. Twoe quivalents of this precursor undergo reaction with one equivalent of [Pt(dbbpy)(CCpy) 2 ]( 3; dbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine, CCpy = 4-pyridylacetylide)a tr oom temperature, furnishing Ir-Pt-Ir trimetallic complex 4a via substitution of the weakly coordinated PF 6 À by the pyridyl groups.…”

“…Previously reported 1a and the Ir precursor [Ir(F 2 ppy) 2 (CNAr dmp )(FPF 5 )] were synthesized as described. [51] Complex 3 was prepared according to the literature procedure. [62] CD 3 CN was used for NMR experiments, owing to the good solubility of the trimetallic complexes 4a-c in this solvent.…”

“…Here, we report an ew synthetic approacht oa ssemble Ir III and Pt II chromophores into supramolecular structures, using the highly reactive cyclometalated iridium synthons Ir(C^N) 2 (CNAr dmp )(FPF 5 )( CNAr dmp = 2,6-dimethylphenylisocyanide) as startingp oints. Precursors of this type include weaklybound PF 6 À anions and were recently discovered by our group and shownt ou ndergo transmetalation with B(C 6 F 5 ) 3 , [51] and here we show that these complexes also allow rapid, highyieldings ynthesis of supramolecular constructs.The complexes we describe in this work partner bis-cyclometalated iridium isocyanide complexes, previously shown by our group to possess favorable redoxa nd photophysical properties, [52,53] with platinum acetylide chromophores. By using reactive Ir precursors and ap yridyl-substituted Pt II bis-acetylidec omplex, a family of Ir-Pt-Ir trimetallic complexesa re obtained in nearquantitative yield at room temperature with minimal workup and no additional purification steps required.…”