Mechanistic investigations via DFT support the cooperative heterobimetallic C–H and O–H bond activation across TaIr multiple bonds

Abstract

Tantalum and iridium join forces to promote the unconventional cooperative activation of unactivated C–H and O–H bonds across the two metals.

Strongly Polarized Iridiumδ−–Aluminumδ+ Pairs: Unconventional Reactivity Patterns Including CO2 Cooperative Reductive Cleavage

“…The hydride resonance is observed as a singlet at δ −16.80 ppm and integrates for 3H. This suggests rapid exchange among the three hydrides on the NMR time scale at room temperature, which is expected on the basis of literature precedents for metal–polyhydride systems. ,,, The IR spectrum of 1 exhibits two strong bands at σ 2144 cm –1 and 1973 cm –1 assigned to metal–hydride stretches. The most significant feature of the crystallographic structure of 1 , shown in Figure , is the Al–Ir distance of 2.406(2) Å, which is the second shortest reported distance for a Ir species bearing an Al atom in its coordination sphere. ,− The only species featuring a shorter Al–Ir bond of 2.382(1) Å is the pincer complex [PAlP]­Ir­(H) 4 (Scheme ) described by Yamashita and co-workers .…”

“…This suggests rapid exchange among the three hydrides on the NMR time scale at room temperature, which is expected on the basis of literature precedents for metal−polyhydride systems. 32,33,35,36 The IR spectrum of 1 exhibits two strong bands at σ 2144 cm −1 and 1973 cm −1 assigned to metal−hydride stretches. The most significant feature of the crystallographic structure of 1, shown in Figure 1, is the Al−Ir distance of 2.406(2) Å, which is the second shortest reported distance for a Ir species bearing an Al atom in its coordination sphere.…”

“…To our surprise, no followup studies emerged from this preliminary work to explore further the reactivity of this unconventional molecular object featuring a low-valent Ir 2 Al 2 core. Very recently, our group reported the preparation of heterobimetallic tantalum–iridium complexes using a similar alkane reductive elimination approach (Scheme , bottom) and demonstrated the ability of the resulting TaIr multiple-bond motif to promote H/D isotope exchange reactions with excellent catalytic performances. − …”

Bifunctional Effect of a Triple-Bond Heterobimetallic Zr/Co System for Hydrogen Activation

“…55−57 However, few theoretical studies focused on the functions and mechanisms of this novel type of heterobimetallic complexes with multiple M−M bonds. 58,59 Very recently, a novel heterobimetallic catalyst was synthesized by Thomas' group using Zr and Co as metal centers. 60−62 In the Zr/Co catalyst, the Zr center combines with two amine ligands, as our conjecture, which may result in a plausible exposed Lewis acidic site.…”

Highly dispersed silica-supported iridium and iridium–aluminium catalysts for methane activation prepared via surface organometallic chemistry

“…11,12 Our contribution to this field was the discovery of original silicasupported Ta/Ir catalysts highly active in H/D exchange reactions of arenes, and prepared from molecular heterobimetallic complexes isolated in solution. [13][14][15] We recently described the synthesis of an original iridiumaluminium complex, [(Cp*IrH 3 ) 3 Al], 1 (Scheme 1), and have demonstrated the lability of the [Cp*IrH 3 ] − iridate moieties surrounding the Al(III) cation, notably in presence of protic species. 16 We hypothesized that such protonolysis reactivity could be used with profit for the grafting of 1 onto silica.…”