Carbon–Hydrogen Bond Activation, C–N Bond Coupling, and Cycloaddition Reactivity of a Three-Coordinate Nickel Complex Featuring a Terminal Imido Ligand

Abstract

The three-coordinate imidos (dtbpe)Ni=NR (dtbpe = tBu2PCH2CH2PtBu2, R = 2,6-iPr2C6H3, 2,4,6-Me3C6H2 (Mes), and 1-adamantyl (Ad)), which contain a legitimate Ni–N double bond as well as basic imido nitrogen based on theoretical analysis, readily deprotonate HC≡CPh to form the amide acetylide species (dtbpe)Ni{NH(Ar)}(C≡CPh). In the case of R = 2,6-iPr2C6H3, reductive carbonylation results in formation of the (dtbpe)Ni(CO)2 along with the N–C coupled product keteneimine PhCH=C=N(2,6- iPr2C6H3). Given the ability of the Ni=N bond to have biradical character as suggested by theoretical analysis, H atom abstraction can also occur in (dtbpe)Ni=N{2,6-iPr2C6H3} when this species is treated with HSn(nBu)3. Likewise, the microscopic reverse reaction—conversion of the Ni(I) anilide (dtbpe)Ni{NH(2,6-iPr2C6H3)} to the imido (dtbpe)Ni=N{2,6-iPr2C6H3}—is promoted when using the radical Mes*O• (Mes* = 2,4,6-tBu3C6H2). Reactivity studies involving the imido complexes, in particular (dtbpe)Ni=N{2,6-iPr2C6H3}, are also reported with small, unsaturated molecules such as diphenylketene, benzylisocyanate, benzaldehyde, and carbon dioxide, including the formation of C–N and N–N bonds by coupling reactions. In addition to NMR spectroscopic data and combustion analysis, we also report structural studies for all the cycloaddition reactions involving the imido (dtbpe)Ni=N{2,6-iPr2C6H3}.

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

“…In nickel chemistry, it is generally observed that small 2 J P, P (i.e.,2 -30 Hz) correspond to nickel(II) complexes, whereas larger 2 J P, P (i.e.,4 5-80 Hz) correspond to nickel(0) complexes. [10,11,22,[77][78][79][80][81][82][83][84] However, exceptionst ot his trend have been reported by ourselves [10] and others. [84,85] Moreover,this approach is limited to asymmetric speciesb ecause 2 J P, P cannotb eo bserved in complexes such as 4 and 7 due to symmetry.…”

The “Metallo”‐Diels–Alder Reactions: Examining the Metalloid Behavior of Germanimines

“…A [4+2] cycloaddition product ( 7 , see Supporting Information) is also observed for benzophenone. In contrast, TM–imido complexes undergo [2+2] cycloadditions with benzaldehyde or benzophenone …”

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.…”