Cationic Iridium(I) NHC‐Phosphinidene Complexes and Their Application in Hydrogen Isotope Exchange Reactions

Abstract

The reaction of the dimeric iridium complex [Ir(cod)Cl]2 (cod=1,5‐cyclooctadiene) with the N‐heterocyclic carbene‐phosphinidene adduct (IDipp)PH (1, IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene) afforded the neutral bimetallic iridium(I) complex [μ‐{(IDipp)PH}{Ir(cod)Cl}2] (2), and further addition of IDipp(PH) (1) yielded the corresponding monometallic iridium(I) complex [{(IDipp)PH}Ir(cod)Cl] (3). Dechlorination of these complexes with sodium tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate (NaBArF4) yielded their cationic derivatives [{μ‐(IDipp)PH}{Ir(cod)}2{μ‐Cl}][BArF4] (4) and [{(IDipp)PH}Ir(cod)(PPh3)][BArF4] (5). All complexes were structurally characterized and showed the expected square‐planar coordination geometry and significant polarization of the P−C bond of the NHC‐phosphinidene adduct upon metal coordination. The complexes 4 and 5 were tested for their applicability in catalytic H/D exchange reactions, and both complexes showed high activity for a broad range of aromatic substrates, ranging from ketones, amides, esters, nitro compounds and heterocycles.

Copper and Silver Complexes of N‐Heterocyclic Carbene‐Parent Phosphinidene Adducts

“…[3] Moreover, the resonance structures A and B have one or two phosphorus lone pairs, [4] respectively, available for metal coordination, and accordingly, numerous mono-and bimetallic transition metal complexes have been isolated in the recent past. [5,[6][7][8][9] This ambiguity was also demonstrated for coinage metal complexes, and bimetallic complexes of the type [{(IMes)PPh}(MCl) 2 ] (I, M = Cu, Ag, Au) were isolated and structurally characterized (Figure 1). [10] It should be noted, however, that only the gold(I) complexes of type I proved monomeric in the solid state, whereas the copper(I) and silver(I) analogues formed octanuclear species with aggregation through M 2 (μ 2 -Cl) 2 units.…”

“…[12] In our hands, the (NHC)PH derivatives (IMes)PH (1 a) [7,14] and (IDipp)PH (1 b) [15,16] have been prepared through the reaction of the 2,2-difluoroimidazolines (IMes)F 2 and (IDipp)F 2 with P-(SiMe 3 ) 3 , followed by desilylation of the trimethylsilylphosphinidene adducts (IMes)PSiMe 3 and (IDipp)PSiMe 3 . [16][17][18] In continuation of our studies on the coordination chemistry of 1 a and 1 b towards transition and main-group metals, [6,8,9,17] we would like to present in this contribution the preparation and structural characterization of monometallic copper(I) and silver(I) complexes containing these NHC-parent phosphinidene adducts. Attempts to prepare bimetallic complexes were also performed but proved less successful, as these complexes are significantly less stable and tend to decompose with elimination of the NHC-phosphinidene ligand.…”