The reaction of the 2-(trimethylsilyl)imidazolium triflate 9 with diarylboron halides (4-R-C H ) BX (R=H, X=Br; R=CH , X=Cl; R=CF , X=Cl) afforded the NHC-stabilized borenium cations 10 a-c. Cyclic voltammetry revealed a linear correlation between the Hammett parameter σ of the para substituent and the half-wave potential. Chemical reduction with decamethylcobaltocene, [(C Me ) Co], furnished the corresponding radicals 11 a-c; their characterization by EPR spectroscopy confirmed the paramagnetic character of 11 a-c, with large hyperfine coupling constants to the boron isotopes B and B, while delocalization of the unpaired electron into the NHC is negligible. DFT calculations of the percentage of spin density distribution between the carbene (NHC) and the boryl fragments (BR ) revealed for 11 a-c a spin density ratio (BR /NHC) of ca. 9:1, which underlines their distinct boryl radical character. The molecular structure of the most stable species 11 c was established by X-ray diffraction analysis.

Die Reaktion von 2-(Trimethylsilyl)imidazoliumtriflat 9 mit Diarylborhalogeniden (4-R-C 6 H 4 ) 2 BX (R = H, X = Br;R = CH 3 ,X = Cl;R = CF 3 ,X = Cl) führte zu den NHC-stabilisierten Boreniumkationen 10 a-c.C yclovoltammetrische Untersuchungen offenbarten eine lineare Korrelation zwischen den Hammett-Parametern s p der para-Substituenten und den Halbstufenpotentialen. Die chemische Reduktion mittels Decamethylcobaltocen, [(C 5 Me 5 ) 2 Co],l ieferte die entsprechenden Radikale 11 a-c;ihre Charakterisierung durch EPR-Spektroskopie bestätigte den paramagnetischen Charakter von 11 a-c und ergab große Hyperfeinkopplungskonstanten zu den Bor-Isotopen 11 Bu nd 10 B, während die Delokalisierung des ungepaarten Elektrons in das NHC vernachlässigbar ist. DFT-Berechnungen der Anteile der Spindichteverteilung zwischen dem Carben (NHC) und dem Borylfragment (BR 2 )o ffenbarte für 11 a-c ein Spindichteverhältnis (BR 2 /NHC) von ca. 9:1, wodurch ihr eindeutiger Borylcharakter unterstrichen wird. Die Molekülstruktur der stabilsten Spezies 11 c wurded urchR çntgenstrukturanalyse bestimmt.

The feasibility of additive manufacturing (AM) to produce industrial components, also for the oil and gas industry, has been demonstrated in the past. Therefore, current research efforts focus on demonstrating the reliability of AM materials subjected to demanding service conditions. In this regard, special attention has been paid to its corrosion resistance in harsh environments as one of the most critical properties in these applications. The beneficial combination of high strength, excellent thermal stability, and outstanding corrosion resistance makes alloy 718 (UNS N07718) the most used wrought and AM nickel alloy in the oil and gas industry. Wrought 718 has an extensive record of field performance in demanding oil and gas applications including directional drilling tools that undergo extreme mechanical loads in corrosive drilling fluids. On the other hand, limited data regarding the corrosion behavior of AM718 in typical drilling environments has been collected so far. In this research work, the pitting susceptibility of selective laser melted alloy 718 in simulated drilling environments has been studied.Open circuit potential measurements as well as cyclic potentiodynamic and potentiostatic polarization tests were used to characterize the pitting corrosion resistance of AM718 in alkaline brines at elevated temperatures. In addition, microstructural particularities in alloy 718 were investigated to explain the observed differences in the electrochemical behaviors.