Activation of Small Molecules at Nickel(I) Moieties

Abstract

The activation and selective transformation of virtually inexhaustible or easy-to-generate chemicals like N, O, CO, CO, H, or methane gas to value-added products is a lively area of current research, because of its economic relevance as well as its huge ecological impact. Biologists and chemists have put forth a lot of effort toward understanding and modeling the mechanisms of biological small-molecule activation, and in several catalytic cycles proposed for nickel-containing enzymes, nickel(I) plays a key role. In recent years also in synthetic chemistry the huge potential of complex nickel(I) units for the activation and transformation of small molecules has been discovered and exploited. This Perspective highlights some representative examples of nickel(I)-based small-molecule activation, intending to establish awareness of the competencies and scope of nickel(I) compounds.

A Biomimetic Nickel Complex with a Reduced CO2 Ligand Generated by Formate Deprotonation and Its Behaviour towards CO2

“…The unusual electronic situation in 2 is also reflected in its reactivity: It readily transfers an O 2− equivalent onto added CO 2 to yield nickel‐bound CO and carbonate. Future research will focus on the reaction of 1 with (sub)stoichiometric amounts of K[N(SiMe 3 ) 2 ] as this seems a promising path to enter into nickel(I)‐mediated formate/CO 2 conversion …”

The Importance of Ligand‐Induced Backdonation in the Stabilization of Square Planar d10 Nickel π‐Complexes

“…For example, we are exploring the organometallicc hemistry of nickel, [10][11][12][13][14] which has undergone ar enaissance in recent years. [15][16][17][18][19][20][21] Our focus has been the structure and reactivityo fn ickel p-complexes, which have been reported in aw ide range of catalytic processes, including the coupling of CO 2 and ethylene, [5,[22][23][24][25][26][27][28][29][30][31][32] intermolecular Tischenkoc oupling, [33][34][35] benzoxasilole synthesis, [36,37] the aldol reaction, [38] allylic alkylation, [39] allylic amination, [40] allylic amidation, [41] epoxide functionalization, [42] and Suzuki-Miyaura coupling. [43] Nickel p-complexes of heteroarenes have also been identified as key intermediates in nickel-catalysed catalystt ransfer polycondensation to form polythiophenes.…”

Theoretical prediction of Ni(I)‐catalyst for hydrosilylation of pyridine and quinoline

“…[24][25][26][27][28][29] For instance, Zimmermann and Limberg suggested that Ni(I) complexes could be useful for activating small molecules. [27] The reason for this was attributed to the fact that the monovalent nickel has a half-filled d-orbital which can be utilized for activating substrate by transferring electron density. [27] However, +I oxidation state of Ni is quite unusual and the number of isolated and/or fully characterized Ni(I) complexes which show activity toward catalytic reaction has been still quite limited in literature.…”

“…[27] The reason for this was attributed to the fact that the monovalent nickel has a half-filled d-orbital which can be utilized for activating substrate by transferring electron density. [27] However, +I oxidation state of Ni is quite unusual and the number of isolated and/or fully characterized Ni(I) complexes which show activity toward catalytic reaction has been still quite limited in literature. Very recently, Lee and Yoo [30] synthesized a T-shaped nickel(I) complex using a rigid acridanebased pincer ligand and suggested that sterically exposed halffilled d x 2 −y 2 orbital of Ni(I) provided unique open-shell reactivity toward such substrates containing double bond as C 2 H 4 and CO 2 .…”