Ammonia Activation by a Nickel NCN‐Pincer Complex featuring a Non‐Innocent N‐Heterocyclic Carbene: Ammine and Amido Complexes in Equilibrium

Abstract

A Ni0‐NCN pincer complex featuring a six‐membered N‐heterocyclic carbene (NHC) central platform and amidine pendant arms was synthesized by deprotonation of its NiII precursor. It retained chloride in the square‐planar coordination sphere of nickel and was expected to be highly susceptible to oxidative addition reactions. The Ni0 complex rapidly activated ammonia at room temperature, in a ligand‐assisted process where the carbene carbon atom played the unprecedented role of proton acceptor. For the first time, the coordinated (ammine) and activated (amido) species were observed together in solution, in a solvent‐dependent equilibrium. A structural analysis of the Ni complexes provided insight into the highly unusual, non‐innocent behavior of the NHC ligand.

On the Ambiphilic Reactivity of Geometrically Constrained Phosphorus(III) and Arsenic(III) Compounds: Insights into Their Interaction with Ionic Substrates

“…1 H, 13 C, 31 P, 19 FNMR spectra were recorded at room temperature using aB ruker AVIII 500 MHz or Bruker AVIII HD NanoBay 400 MHz NMR Spectrometer. 31 PNMR chemical shifts were externally referenced to an 85 %s olution of H 3 PO 4 (aq).…”

“…31 PNMR chemical shifts were externally referenced to an 85 %s olution of H 3 PO 4 (aq). 19 FNMR chemical shifts were externally referenced to CF 3 COOH. Elemental analyses were performed by Elemental analysis Ltd (Devon).…”

“…It is also worth noting that the substrates cope of such compounds includes molecules such as ammonia,which hashistorically provendifficult to activate using precious metalc atalysts due to the unfavourable coordination/activation equilibrium. Newr outes resultingi nt he activation of NÀHb onds in ammonia are particularly appealing, becauseo ft he dearth of transition-metal systems capable of effecting such at ransformation, [7][8][9][10][11][12][13][14][15][16][17][18][19] and the relevance of NÀHa ctivation to an umber of potentially important industrialp rocesses. [20] More recently,g eometrically constrained compounds based on phosphorus(III) have also received significant attention in this field.…”

E–H Bond Activation of Ammonia and Water by a Geometrically Constrained Phosphorus(III) Compound

“…[8] New routes resulting in the activation of NÀHb onds in ammonia are particularly appealing because of the dearth of transition-metal systems capable of effecting such atransformation [9][10][11][12][13][14][15][16][17][18][19][20][21] and the relevance of N À H activation to an umber of potentially important industrial processes. [22] In addition to these high profile examples,r ecent studies have shown that complexes of phosphorus(III) with distorted geometry can cleave arange of polarized EÀHbonds (E=Oor N).…”

“…[9][10][11][12][13][14][15][16][17][18][19][20][21] Therefore,a dvances in main group mediated activation of ammonia are of great interest. [4, 5, 6c-d,24, 26, 27, 30-32] Ther eaction of 1 with ammonia gas (1 atm) results in the quantitative conversion of 1 to anew product, 2 (Scheme 2).…”