Thermally stable N2 and H2 adducts of cationic nickel(ii)

Abstract

The first examples of thermally stable molecular dihydrogen adducts of nickel were synthesized from their dinitrogen adduct precursors, which are themselves among the first examples of Ni(II)-N 2 complexes. The minimal activation of the bound N 2 moieties suggests that these adducts are stabilized predominantly through s-donation from the adduct to the electrophilic metal center. We further show that the bound H 2 ligand can undergo heterolytic cleavage to deliver hydride to the nickel center. The H 2 adducts are of particular interest in the context of hypotheses suggesting that Ni can serve as the site for H 2 binding and heterolytic activation in [NiFe] hydrogenases.

Heterolytic H2 Cleavage and Catalytic Hydrogenation by an Iron Metallaboratrane

“…The hydrogen chemistry of this (TPB)Fe(L) system contrasts with the related nickel 26 and cobalt 24 complexes of TPB, where the metal-boron bond remains intact under an H 2 atmosphere.…”

Hydrogenase Enzymes and Their Synthetic Models: The Role of Metal Hydrides

“…Lastly, the most stable Ni(II)( η 2 -H 2 ) complex to date is {[(2-Ph 2 PC 6 H 4 ) 3 Si]Ni( η 2 -H 2 )} + , which features a tetradentate, anionic SiP 3 -donor tripod. 373 In a sense, this complex mirrors the 5-coordinate Ni(II) center in the (Cys-S) 2 Ni( η 2 -H 2 )(Cys-S) 2 Fe(CN) 2 (CO) species proposed as an enzyme intermediate. While the complexes [ 50 ( η 2 -H 2 )] + and [ 51 ( η 2 -H 2 )] + illustrate biorelevant facets of nickel hydrides, their redox chemistry has not been developed.…”

Leveraging molecular metal–support interactions for H2 and N2 activation

“…In general, Ni tends to be both a poor π-back-donor and poor σ-acceptor toward H 2 ; thus, examples of H 2 reacting with Ni are uncommon [32,39,[46][47][48][49][50]. Classical H 2 oxidative addition at a single Ni center has not been reported to our knowledge, attesting to the poor π-back-donor ability of Ni.…”