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En route to catalysis: Two equivalents of the three‐coordinate copper(II) amide [(Cl2NN)Cu]‐NHAd participate in stoichiometric CH amination by a H‐atom abstraction/radical capture sequence. This active species may be generated through a copper(II) tert‐butoxide intermediate to allow for the unprecedented catalytic amination of sp3‐CH bonds with unactivated alkylamines. This method greatly expands the range of amines for catalytic CH amination since most protocols require N‐based electron‐withdrawing groups.

The new iron(II)-thiolate complexes [(iPrBIP)FeII(SPh)(Cl)] (1) and [(iPrBIP)FeII(SPh)(OTf)] (2) (BIP = bis(iminopyridine)) were prepared as models for cysteine dioxygenase (CDO), which converts Cys to Cys-SO2H at a (His)3FeII center. Reaction of 1 and 2 with O2 leads to Fe-oxygenation and S-oxygenation, respectively. For 1 + O2, the spectroscopic and reactivity data, including 18O isotope studies, are consistent with an assignment of an iron(IV)-oxo complex as the product of oxygenation ([(iPrBIP)FeIV(O)(Cl)] (3)). In contrast, 2 + O2 results in direct S-oxygenation to give a sulfonato product (PhSO3−). The positioning of the thiolate ligand in 1 versus 2 appears to play a critical role in determining the outcome of O2 activation. The thiolate ligands in 1 and 2 are essential for O2 reactivity, and exhibit an important influence over the FeIII/FeII redox potential.

New water-soluble pentamethylcyclopentadienyl cobalt(III) complexes with proton-responsive 4,4'- and 6,6'-dihydroxy-2,2'-bipyridine (4DHBP and 6DHBP, respectively) ligands have been prepared and were characterized by X-ray crystallography, UV-vis and NMR spectroscopy, and mass spectrometry. These cobalt(III) complexes with proton-responsive ligands predominantly exist in their deprotonated [Cp*Co(DHBP-2H(+))(OH2)] forms with stronger electron-donating properties in neutral and basic solutions, and are active catalysts for CO2 hydrogenation in aqueous bicarbonate media at moderate temperature under a total 4-5 MPa (CO2:H2 1:1) pressure. The cobalt complexes containing 4DHBP ligands ([1-OH2](2+) and [1-Cl](+), where 1 = Cp*Co(4DHBP)) display better thermal stability and exhibit notable catalytic activity for CO2 hydrogenation to formate in contrast to the catalytically inactive nonsubstituted bpy analogues [3-OH2](2+) (3 = Cp*Co(bpy)). While the catalyst Cp*Ir(6DHBP)(OH2)(2+) in which the pendent oxyanion lowers the barrier for H2 heterolysis via proton transfer through a hydrogen-bonding network involving a water molecule is remarkably effective (ACS Catal. 2013, 3, 856-860), cobalt complexes containing 6DHBP ligands ([2-OH2](2+) and [2-Cl](+), 2 = Cp*Co(6DHBP)) exhibit lower TOF and TON for CO2 hydrogenation than those with 4DHBP. The low activity is attributed to thermal instability during the hydrogenation of CO2 as corroborated by DFT calculations.

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).