Cleavage of acyclic diaminocarbene ligands at an iridium(iii) center. Recognition of a new reactivity mode for carbene ligands

Abstract

A new reactivity mode for acyclic diaminocarbene ligands, viz. competitive cleavage of either C–NH2 or C–NHR bonds in the aminocarbene fragment, is recognized.

Phosphorescent Iridium(III) Complexes with Acyclic Diaminocarbene Ligands as Chemosensors for Mercury

“…Replacement of chloride in 4a – d with 1 equiv of isocyanide led to the mixed isocyanide/diaminocarbene species [ 5a – d ]­(OTf) (78–84%). Bis-CNR complexes [Ir­(ppy) 2 (CNC 6 H 4 -4-X) 2 ]­(OTf) ([ 6a – d ]­(OTf); 72–87%) were obtained from the reaction of 1 with 4 equiv of 2a – d in the presence of 2 equiv of AgOTf as previously described …”

“…The coupling of bis-CNR [Ir­(ppy) 2 (CNC 6 H 4 X) 2 ]­(OTf) complexes [ 6a – d ]­(OTf) with an excess of gaseous NH 3 afforded the known bis-ADC complexes [Ir­(ppy) 2 {C­(NH 2 )­NHC 6 H 4 -4-X} 2 ]­(OTf) ( 7a – d ) and cyanide/ADC [Ir­(ppy) 2 (CN)­{C­(NH 2 )­NHC 6 H 4 -4-X}]­(OTf) ( 8a – d ) . New complexes 3a – d and 4a – d were characterized by elemental analyses (C, H, N), high-resolution ESI + -MS, TG/DTA, and IR and 1 H, 13 C­{ 1 H}, and 19 F­{ 1 H} NMR spectroscopy (see section S4 in the Supporting Information for more details).…”

“…Alteration of the photophysical properties by the change of the secondary ancillary ligands present in the coordination sphere of sensor species is less common but worth exploring. Recently, we reported on cyclometalated iridium­(III) complexes containing ancillary acyclic diaminocarbene ligands (ADCs), which were generated via the addition of N-donor species to metal-activated isocyanides (for reviews see ref ; for the representative synthetic works see ref ). In the current study, we expanded this synthetic approach toward new iridium­(III) ADC species and evaluated their electrochemical and photophysical properties.…”

Tuning the luminescence of transition metal complexes with acyclic diaminocarbene ligands

“…Metal-mediated addition of NH 3 to the coordinated isocyanides in 22-29 (Scheme 5) allows the preparation of another family of heteroleptic cyclometallated Ir(III) species bearing ancillary ADCs. 28,68 Oxidation the thus prepared ADCs 30-45 manifests by an irreversible wave centred at metal (0.77-1.22 V). Conversion of one CNR in 26-29 to ADC in 34-37 brings about the decrease in the oxidation potential by ca.…”

“…The first example of an emissive transition metal ADC complex was reported by Che and coworkers for Pt ii species in the late 90s, 67 but an explosion of research in this area took place several years ago, starting with the discovery of Ir iii –ADC complexes by Teets 56 and Luzyanin 68 groups. Of note, some of the complexes depicted below feature deprotonated forms of ADCs, that are called aminocarbenes for the sake of simplicity of the discussion; some authors suggest that they should be called formamidinyl or aminocarbene-like species from the perspective of organometallic formalism.…”