Transient Terminal Cu−Nitrene Intermediates from Discrete Dicopper Nitrenes

Abstract

Reaction of the copper(I) beta-diketiminate {[Me3NN]Cu}2(mu-toluene) with the aryl azide N3Ar (Ar = 3,5-Me2C6H3) in toluene results in immediate effervescence and formation of the dicopper nitrene {[Me3NN]Cu}2(mu-NAr) (2) in 77% yield. The X-ray structure of 2 shows nearly symmetric bonding of the nitrene to two Cu centers separated by 2.911(1) A with Cu-N distances of 1.794(5) and 1.808(5) A along with a Cu-N-Cu angle of 107.8(2) degrees . This structure is conceptually related to the dicopper carbenes {[MexNN]Cu}2(mu-CPh2) (x = 2 or 3) (Dai, X.; Warren J. Am. Chem. Soc. 2004, 126, 10085. Badiei, Y. M.; Warren J. Organomet. Chem. 2005, 690, 5989.) which exhibit shorter Cu-Cu distances (2.4635(7) or 2.485(1) A) and acute Cu-C-Cu angles (79.51(14) or 80.1(2) degrees ). Addition of the Cu(I) anilidoimine {[Me2AI]Cu}2 (prepared from CuOtBu and the aniline-imine H[Me2AI] in 77% yield) to a benzene-d6 solution of 2 results in the formation of two new anilidoimine complexes {[Me2AI]Cu(mu- NAr)Cu[Me3NN] (5) and {[Me2AI]Cu}2(mu-NAr) (6) as well as [Me3NN]Cu(benzene) over 3 h. These observations are consistent with the slow dissociation of a [Me3NN]Cu fragment from 2 to generate the transient terminal nitrenes [Me3NN]Cu=NAr and [Me2AI]Cu=NAr quickly trapped by the [Me2AI]Cu fragment to form the new unsymmetrical and symmetrical dicopper nitrenes 5 and 6. Preliminary reactivity studies indicate electrophilic reactivity at the nitrene moiety. Dicopper nitrene 2 reacts with 10 equiv PMe3 and CNtBu to give ArN=PMe3 and ArN=C=NtBu in 94% and 92% yields, respectively, with concomitant formation of [Me3NN]Cu(L) (L = PMe3 and CNtBu). Reaction between 2 and 2 equiv PMe3 allows for observation of the structurally characterized Cu(I) phosphaimide [Me3NN]Cu(ArN=PMe3) (7).

Formation of CC and CN Bonds in NiII Ketimide Complexes via Transient NiIII Aryl Imides

“…In addition, Holland and co-workers have described the ability of Fe III imides to abstract H atoms from the ligand or external reagents, [35] while the Warren group has described the reactivity of Cu aryl imides. [36] Herein, we report the oxidation a Ni I synthon by aryl azides. In contrast to the alkyl azides, which give Ni III imides, these reactions proceed to effect internal electrontransfer reactions affording the formation of new C À C or C À N bonds, thus resulting in products that are described as Ni II ketimides.…”

C–H Functionalization Reactivity of a Nickel–Imide

“…11 The β-diketiminato copper(I) complex {[Cl 2 NN]Cu} 2 (μ-benzene) also catalytically aminates C−H bonds in hydrocarbons (R−H) to give amines (HN(R)Ad) in high yields using N 3 Ad as the nitrene transfer reagent (Scheme 2). 11,29 In light of the efficient stoichiometric and catalytic C−H amination by its copper analogue and the aforementioned computational studies of nickel complexes, we reinvestigated the reactivity of [Me 3 NN]NiNAd (1) with benzylic C−H substrates. Specifically, we were interested in the potential to couple previously observed HAA and C−N bond forming reactions (Scheme 1) in a complete C−H functionalization sequence employing a single substrate R−H to give the new amine R−NHAd.…”

Binuclear β-diketiminate complexes of copper(i)

“…[3][4][5][6][7][8][9][10][11][12][13][14][15] Warren and coworkers have expanded the oxidation chemistry of copper(I) β-diketiminate complexes to include diazoalkanes, PhI=NTs, organoazides and tert-butylperoxide. [16][17][18][19][20][21][22][23][24][25][26][27][28] These stoichiometric studies are part of a broader programme, developing exciting synthetic protocols for the functionalization of carbon-hydrogen bonds in hydrocarbons. The catalytic generation of a monomeric copper nitrene intermediate and its transformation to a copper(II) amide by hydrogen atom abstraction has been proposed as a key step in the transformation of carbon-hydrogen bonds to carbon-nitrogen bonds.…”

“…The catalytic generation of a monomeric copper nitrene intermediate and its transformation to a copper(II) amide by hydrogen atom abstraction has been proposed as a key step in the transformation of carbon-hydrogen bonds to carbon-nitrogen bonds. 20,[22][23][24]26 Similarly, a copper(II) alkoxide is proposed as a crucial intermediate during the oxidation of cyclohexane to tert-butyl-cyclohexyl ether by tert-butylperoxide in the presence of a copper(I) diketiminate complexes. 25 In more recent years, the chemistry of copper β-diketiminate has been expanded to include both dinucleating and trinucleating ligands.…”