Strongly Polarized Iridium^δ−–Aluminum^δ+ Pairs: Unconventional Reactivity Patterns Including CO₂ Cooperative Reductive Cleavage

Abstract

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.

Electrophilic Aromatic Substitution: theoretical insight into halonium ion self-existence in catalytic system

“…We have observed such a trend in this example, where it can be seen that the last three values (fourteenth to sixteenth scan step) have much lower energy than the rest of the plot. In examining the last three scan steps, we observed something that, to our knowledge, has not been reported in the literature -the formation of tribromooxyfluoroiron(V) fluoride (Figure 13a) [42]. Such a transition from iron(III) to iron(V) can only be described for inorganic species, and that is by passing iron(III) compounds through the current of a very strong oxidizing agent.…”

“…Using semiempirical PM7 methods, we were able to discover a type of noncovalent interaction that appears to control the outcome of the experimental procedure in these systems. In the studies carried out with PM7 functionality, we have succeeded in finding and localizing interactions that were not known in the chemical community since the recently published work on the topic of the bimetallic catalytic process between the interactions between transition and main group metals [42,49]. Based on the same mechanistic principles, we have solved for the first time a stabilizing interaction between transition metal -halogen ion pair where the halogen serves as the electrophilic species, which is different from the textbook predictions at the theoretical level for this type of complexes/ catalytic species.…”

Cooperative C–H Bond Activation by a Low-Spin d6 Iron–Aluminium Complex

“…For example, 3a readily reacts with pyridine (1 equiv., C6D6, room temperature) resulting in the selective C-H activation in the 2position of the heterocycle (> 95% NMR yield, Figure 6a). Like 4a, 5a exhibits a sharp singlet resonance in the 31 P{ 1 H} NMR spectrum at P = 29.6 ppm as well as a broadened quartet hydride signal at H = -15.33 ppm in the 1 H NMR spectrum. The reaction of 2b with pyridine required more forcing reaction conditions (40 °C, 10 equiv.…”

1st Row Transition Metal Aluminylene Complexes: Preparation, Properties and Bonding Analysis

“…[2][3][4][5] For example, the inclusion of aluminium sites in pincer complexes of group 9 or 10 metals has led to new catalysts based on X-type aluminyl † metalloligands for alkane dehydrogenation, 6 the hydroarylation of alkenes with pyridine, 7 the magnesiation of aryl fluorides, 8 and the activation of CO2. [9][10][11] Related Z-type aluminium ligands have been shown to influence the catalytic competency of nickel metal-centres for alkene hydrogenation. 12 For our part, we have been interested in the development of L-type aluminylene ‡ ligands derived from low-valent aluminium(I) compounds and their role in the catalytic functionalisation of C-H, C-O and C-F bonds (Figure 1).…”