The greenhouse gas sulfur hexafluoride is the common standard example in the literature of a very inert inorganic small molecule that is even stable against O2 in an electric discharge. However, a reduced β-diketiminate nickel species proved to be capable of converting SF6 into sulfide and fluoride compounds at ambient standard conditions. The fluoride product complex features an unprecedented [NiF](+) unit, where the Ni atom is only three-coordinate, while the sulfide product exhibits a rare almost linear [Ni(μ-S)Ni](2+) moiety. The reaction was monitored applying (1)H NMR, IR and EPR spectroscopic techniques resulting in the identification of an intermediate nickel complex that gave insight into the mechanism of the eight-electron reduction of SF6.

In metal-mediated O activation, nickel(II) compounds hardly play a role, but recently it has been shown that enzymes can use nickel(II) for O activation. Now a low-coordinate Lewis acidic nickel(II) complex has been synthesized that reacts with O to give a nickel(II) organoperoxide, as proposed for the enzymatic system. Its formation was studied further by UV/Vis absorption spectroscopy, leading to the observation of a short-lived intermediate that proved to be reactive in both oxygen atom transfer and hydrogen abstraction reactions, while the peroxide efficiently transfers O atoms. Both for the enzyme and for the functional model, the key to O activation is proposed to represent a concomitant electron shift from the substrate/co-ligand.

The complexes [LtBuNi(OCO‐κ2O,C)]M3[N(SiMe3)2]2 (M=Li, Na, K), synthesized by deprotonation of a nickel formate complex [LtBuNiOOCH] with the corresponding amides M[N(SiMe3)2], feature a NiII−CO22− core surrounded by Lewis‐acidic cations (M+) and the influence of the latter on the behavior and reactivity was studied. The results point to a decrease of CO2 activation within the series Li, Na, and K, which is also reflected in the reactivity with Me3SiOTf leading to the liberation of CO and formation of a Ni−OSiMe3 complex. Furthermore, in case of K+, the {[K3[N(SiMe3)2]2}+ shell around the Ni−CO22− entity was shown to have a large impact on its stabilization and behavior. If the number of K[N(SiMe3)2] equivalents used in the reaction with [LtBuNiOOCH] is decreased from 3 to 0.5, the deprotonated part of the precursor enters a complex reaction sequence with formation of [LtBuNiI(μ‐OOCH)NiILtBu]K and [LtBuNi(C2O4)NiLtBu]. The same reaction at higher concentrations additionally led to the formation of a unique hexanuclear NiII complex containing both oxalate and mesoxalate ([O2C‐CO2‐CO2]4−) ligands.

Das Klimagas Schwefelhexafluorid ist in der Literatur ein viel verwendetes Standardbeispiel für ein sehr reaktionsträges anorganisches Molekül, das selbst durch Disauerstoff in einer elektrischen Entladung nicht angegriffen wird. Dennoch sind reduzierte b-Diketiminato-Nickel-Komplexe unter Standardbedingungen in der Lage, SF 6 in Fluorido-und Sulfido-Verbindungen zu überführen. Das Fluorido-Produkt besitzt dabei eine präzedenzlose [NiF] + -Einheit, bei der das Nickelatom nur dreifach koordiniert ist. Der Sulfido-Komplex beinhaltet eine seltene nahezu lineare [Ni(m-S)Ni] 2+ -Anordnung. Die Reaktion wurde mittels 1 H-NMR-, IR-und ESRspektroskopischen Methoden untersucht. Diese führten zur Identifizierung einer Zwischenstufe und gewährten so einen Einblick in den Mechanismus der 8-Elektronen-Reduktion von SF 6 .

The reduction of the β-diketiminato nickel(II) halide complex [L tBu Ni II Br] [L tBu = CH(CtBuNdipp) 2 -, dipp = 2,6-diisopropylphenyl] with potassium sources proceeds via the initial formation of [(L tBu Ni I ) x (μ-Br) x K x ] aggregates, which could be isolated and characterized for x = ϱ and 6. The KBr equivalents readily give way to external donors or substrates to be activated at the central nickel(I) atoms. To test, in how far the steric bulk induced by the residues at [L tBu ]influences the formation of the KBr adducts β-diketiminato ligands with less steric congestion, namely L Me6 and L Me7 [L Me6 = CH(CMeNdmp) 2 -, L Me7 = CMe(CMeNdmp) 2 -, dmp = 2,6-dimethylphenyl] were employed. Through deprotonation of HL Me6 with * Prof. Dr. Christian Limberg E-Mail: christian.limberg@hu-berlin.de [a]