Cooperative Bond Activation and Facile Intramolecular Aryl Transfer of Nickel–Aluminum Pincer‐type Complexes

Abstract

Pincer‐type nickel–aluminum complexes were synthesized using two equivalents of the phosphinoamide, [PhNCH2PiPr2]−. The Ni0–AlIII complexes, {(MesPAlP)Ni}2(μ‐N2) and {(MesPAlP)Ni}2(μ‐COD), where MesPAlP is (Mes)Al(NPhCH2PiPr2)2, were structurally characterized. The (PAlP)Ni system exhibited cooperative bond cleavage mediated by the two‐site Ni–Al unit, including oxidative addition of aryl halides, H2 activation, and ortho‐directed C−H bond activation of pyridine N‐oxide. One intriguing reaction is the reversible intramolecular transfer of the mesityl ring from the Al to the Ni site, which is evocative of the transmetalation step during cross‐coupling catalysis. The aryl‐transfer product,(THF)Al(NPhCH2PiPr2)2Ni(Mes), is the first example of a first‐row transition metal–aluminyl pincer complex. The addition of a judicious donor enables the Al metalloligand to convert reversibly between the alane and aluminyl forms via aryl group transfer to and from Ni, respectively. Theoretical calculations support a zwitterionic Niδ−–Alδ+ electronic structure in the nickel–aluminyl complex.

Amplifying Reactivity of Metal Hydrides: A Heterotrimetallic NiAl2(μ2-H)2 Catalyst for the Dearomatization of N-Heterocycles

“…In the interest of further exploring cooperative transformations in multimetallic assemblies, well-defined heterometallic species incorporating Earth-abundant metals have been of interest with several relevant examples reported in the past decade. − Nickel–alane complexes have been of particular interest given the wide breadth of catalytic ability by nickel and the successful use of aluminum additives as cocatalysts (Figure b). − However, Al is coordinatively saturated in most examples, rendering its primary role to modulating the electron density at the transition metal.…”

Amplifying Reactivity of Metal Hydrides: A Heterotrimetallic NiAl2(μ2-H)2 Catalyst for the Facile Dearomatization of N-Heterocycles

“…[25][26][27][28] Nickelalane complexes have been of particular interest given the wide breadth of catalytic ability by nickel and the successful usage of aluminum additives as cocatalysts (Figure 1b). [29][30][31] However, Al is coordinatively saturated in most examples, rendering their primary role to modulating the electron density at the transition metal.…”