The iridium tetrahydride complex Cp*IrH4 reacts with a range of isobutylaluminum derivatives of general formula Al­(iBu) x (OAr)3–x (x = 1, 2) to give the unusual iridium aluminum species [Cp*IrH3Al­(iBu)­(OAr)] (1) via a reductive elimination route. The Lewis acidity of the Al atom in complex 1 is confirmed by the coordination of pyridine, leading to the adduct [Cp*IrH3Al­( i Bu)­(OAr)­(Py)] (2). Spectroscopic, crystallographic, and computational data support the description of these heterobimetallic complexes 1 and 2 as featuring strongly polarized Al­(III)δ+–Ir­(III)δ− interactions. Reactivity studies demonstrate that the binding of a Lewis base to Al does not quench the reactivity of the Ir–Al motif and that both species 1 and 2 promote the cooperative reductive cleavage of a range of heteroallenes. Specifically, complex 2 promotes the decarbonylation of CO2 and AdNCO, leading to CO (trapped as Cp*IrH2(CO)) and the alkylaluminum oxo ([(iBu)­(OAr)­Al­(Py)]2(μ-O) (3)) and ureate ({Al­(OAr)­( i Bu)­[κ2-(N,O)­AdNC­(O)­NHAd]} (4)) species, respectively. The bridged amidinate species Cp*IrH2(μ-CyNC­(H)­NCy)­Al­( i Bu)­(OAr) (5) is formed in the reaction of 2 with dicyclohexylcarbodiimine. Mechanistic investigations via DFT support cooperative heterobimetallic bond activation processes.

We report an original alkane elimination approach, entailing the protonolysis of triisobutylaluminium by the acidic hydrides from Cp*IrH4. This strategy allows access to a series of well-defined tri-and tetranuclear iridium aluminium polyhydride clusters, depending on the stoichiometry: 3) and [(Cp*IrH3)3Al] (4). Contrary to most transition metal aluminohydride complexes which can be considered as [AlHx+3] xaluminates and LnM + moieties, the situation here is reversed: these complexes have original structures which are best described as [Cp*IrHx] n-iridate units surrounding cationic Al(III) fragments. This is corroborated by reactivity studies, which show that the hydrides are always retained at the iridium sites and that the [Cp*IrH3] -moieties are labile and can be transmetallated to yield potassium ([KIrCp*H3], 8) or silver (([AgIrCp*H3]n, 10) derivatives of potential synthetic interest. DFT calculations show that the bonding situation can vary in these systems, from 3-centre 2-electron hydride-bridged Lewis adducts of the form Ir-H⇀Al, to direct polarized metal-metal interaction from donation of d-electrons of Ir to the Al metal, and both types of interactions are at place to some extent in each of these clusters.

The reaction of a bifunctional hydroxy N-heterocyclic carbene (NHC-OH) ligand with alkyl-aluminum(iii) derivatives appears to be dependent on the precursor used. The expected alkoxy-NHC metallated product is indeed obtained with Al(Bu). In contrast, the sterically hindered [Al(Bu)(OAr)] (OAr = 2,6-di-tert-butyl-4-methylphenoxy) displays reactivity at the carbene and affords an imidazolium-aluminate zwitterion. The non-innocence of the Al-NHC motif is further highlighted by the heterolytic cleavage of the phenol O-H bond across the Al-C bond from Al(O-NHC)X derivatives (X = Bu, OAr).

Redox noninnocent ligands enhance the reactivity of the metal they complex, a strategy used by metalloenzymes and in catalysis. Herein, we report a series of copper complexes with the same ligand framework, but with a pendant nitrogen group that spans five different redox states between nitro and amine. Of particular interest is the synthesis of a unprecedented copper­(I)-arylhydroxylamine complex. While hydroxylamines typically disproportionate or decompose in the presence of transition metal ions, the reactivity of this metastable species is arrested by the presence of an intramolecular hydrogen bond. Two-electron oxidation yields a copper­(II)-(arylnitrosyl radical) complex that can dissociate to a copper­(I) species with uncoordinated arylnitroso. This combination of ligand redox noninnocence and hemilability provides opportunities in catalysis for two-electron chemistry via a one-electron copper­(I/II) shuttle, as exemplified with an aerobic alcohol oxidation.

The grafting of an iridium-aluminium precursor onto silica followed by thermal treatment under H2 yields small (<2 nm), narrowly distributed nanoparticles used as catalysts for methane H/D exchange. This Ir-Al/SiO2...