A Terminal Ni(III)−Imide with Diverse Reactivity Pathways

Abstract

The synthesis and structure of the beta-diketiminato Ni(I) lutidine adducts [MexNN]Ni(2,4-lutidine) (x = 2 (2); x = 3 (3)) are described which serve as synthons to the "naked" 13-electron [MexNN]Ni fragments in reactions with N3Ad to give Ni-imido complexes. The singly bridged imide {[Me2NN]Ni}2(mu-NAd) (4) possesses short Ni-Ni (2.506(1) A) and Ni-N(imido) distances (1.732(4)-1.752(4) A). Steric modification of the beta-diketiminate ligand to include an additional methyl group in the N-aryl 4-position affords the Ni(III) terminal imide [Me3NN]Ni=NAd (8) isolated in 52% yield. The X-ray structure of terminal imide 8 reveals a contracted Ni-N(imido) bond distance (1.662(2) A) and an only somewhat bent imido linkage (Ni-N-C = 164.5(2) degrees ) consistent with a significant degree of multiple bond character. Frozen glass EPR studies of 5 indicate a rhombic environment in which one of the signals exhibits strong hyperfine coupling (A = 22 G) to the imido 14N (I = 1) nucleus. The terminal imide 5 undergoes complete imido group transfer to CO and CNBut to give AdNCO and AdNCNBut, respectively, as well as with PMe3 to afford AdN=PMe3. Exemplifying the radical character at the imido N atom, 5 adds to cobaltocene and abstracts a H atom from 1,4-cyclohexadiene to give the Ni(II)-amides [Me3NN]Ni-NAd(eta4-C5H5)CoCp (7) and [Me3NN]Ni-NHAd (8).

Catalytic Tuning of a Phosphinoethane Ligand for Enhanced C−H Activation

“…As the amine is a neutral, labile ligand and the nickel in (dfmpe)Ni(NH(CD)Ar) is formally Ni 0 , displacement of the amine by a group-transfer reagent such as ArN 3 is suggested by literature precedent. [6][7][8] Regeneration of nitrene active species by amine displacement, eq 3, is calculated to be highly exothermic, ∆H reg ) -36.7 kcal/ mol. We have assumed 6-8 that nitrene transfer (eq 3) will be kinetically facile, given its substantial thermodynamic driving force.…”

Trapping of an NiII Sulfide by a CoI Fulvene Complex

“…5,6 A number of late transition metal carbene (CR 2 2-), nitrene (NR 2-), nitride (N 3-), and phosphinidene (PR 2-) complexes have also been reported in recent years. [7][8][9][10][11][12][13][14][15][16][17][18] While a few of these complexes have been isolated, they tend to be extremely reactive, and often can only be observed spectroscopically. [19][20][21][22] Nonetheless, it is clear that synthetic chemists are now beginning to identify the combination of ligand requirements and synthetic procedures that can successfully generate late-metal ligand multiple bonds.…”

A potential role of a substrate as a base for the deprotonation pathway in Rh-catalysed C–H amination of heteroarenes: DFT insights

“…In fact, metal-nitrenoid species are known to be generated in such reactions and a few examples of C-N bond formation upon treatment of the corresponding metal-nitrenoid species with hydrocarbons have also been reported. [25][26][27][28][29] The Scheme 2. Possible mechanism of C-H amination using phenyl azide as the nitrogen source.…”