Electron by electron: Beta-diketiminato nickel(I) complex fragments are capable of activating N(2) through coordination. The resulting complex can be reduced in two single-electron steps, which further activates the N-N bond. The picture shows the structure of the singly reduced complex with mu-eta(1):eta(1)-bound N(2).
Nanostructured Al 2 O 3 powders were prepared by high-energy ball milling of corundum. Both the solid state nuclear magnetic resonance spectra of the Al 3+ ions and the solid state electron paramagnetic resonance spectra of incorporated Fe 3+ ions are governed by noticeable spectral changes dependent on the duration of the mechanical treatment. The quadrupolar parameters of the 27 Al nuclei and the zero-field splitting parameters of the Fe 3+ ions as well as their statistical distributions were determined as functions of the milling time. Structural changes of the Al 2 O 3 matrix were also followed by powder x-ray diffraction and transmission electron microscopy measurements. Direct relations between the structural disorder as obtained by x-ray data and the spin Hamiltonian parameters of both ions could be established.These results suggest that the milled powders consist of nanocrystalline grains embedded in amorphous grain boundaries even for the longest milling time. The grains can be described in terms of ordered AlO 6 -octahedra as in the starting crystalline material exhibiting a slight rhombic distortion. The grain boundaries look like random arrangements of these octahedral units. The specific behaviour of the environment of the Fe 3+ paramagnetic probe points out that such a point defect acts as an activation centre of the amorphization process.
Reaction of [LtBuNiBr] (LtBu = [HC(C(CMe3)NC6H3(iPr)2)2]−) with KC8 in toluene solution yields the complex [LtBuNi(toluene)], 1, where toluene is bound in a η2 mode via a CC unit of the aromatic ring, as revealed by single-crystal X-ray crystallography and DFT calculations (B3LYP/6-31G*). Performing the same reaction in hexane as the solvent did not lead to a traceable product, so that the β-diketiminato ligand system was changed from LtBu to the less bulky LMe (LMe = [HC(CMeNC6H3(iPr)2)2]−). Reduction of [LMeNiBr]2 with KC8 in diethyl ether led to [LMeNi]2, 2, with intramolecular Ni−aryl interactions, while employment of [LMeNi(μ-Br)2Li(thf)2] as a precursor for a reaction with KC8 in OEt2 led to the complex [LMeNi(μ-Br)Li(thf)2]2, 3. Both complexes 2 and 3 could be fully characterized, also with the aid of XRD, and their reactivity with respect to H2 and N2 was examined. It turned out that they oxidatively add H2 to give the known compound [LMeNi(μ-H)]2, I, while the reaction with N2 provides the dinitrogen complex [(LMeNi)2(N2)], 4.
With the background that β-diketiminato zinc complexes efficiently catalyze the CO 2 /epoxide copolymerization via a mechanism involving two catalyst molecules, a ligand system containing two parallel β-diiminato binding sites linked by a xanthene backbone ([ R Xanthdim] 2with residues R ) 2,3-dimethylphenyl and 2,4-difluorophenyl at the iminato units, respectively) was investigated with respect to its zinc coordination chemistry. The corresponding diimines [ R Xanthdim]H 2 were treated with diethylzinc to yield the complexes [ Me2C6H3 Xanthdim](ZnEt) 2 , 4, and [ F2C6H3 Xanthdim](ZnEt(thf)) 2 , 5, respectively. In order to convert these compounds into polymerization catalysts, they were subsequently treated with SO 2 , which indeed resulted in the corresponding ethylsulfinates. Due to aggregation via intermolecular bridging of ethylsulfinate ligands, the product after the reaction of 5 represents an insoluble coordination polymer. Aggregation does take place also for the primary product obtained from the reaction of 4, as evidenced by the isolation of the tetramer [{[ Me2C6H3 Xanthdim]Zn 2 (µ-O 2 SEt)}µ-O 2 SEt] 4 , 6, and the precipitation of an insoluble solid on storing of such mixtures. 4, 5, and 6 display moderate activities as catalysts for the copolymerization of cyclohexene oxide and CO 2 . A bimodal molecular weight distribution points to two effective mechanisms, one of which probably involves two cooperating Zn centers as anticipated. Possible structural reasons for these catalytic results are discussed.
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