Endlich homoleptisch: Synthese und vollständige Charakterisierung stabiler Salze des Mangantetranitrosylkations

Chasing the Mond Cation: Synthesis and Characterization of the Homoleptic Nickel Tetracarbonyl Cation and its Tricarbonyl-Nitrosyl Analogue

130 years after Mond discovered the first homoleptic carbonyl complex Ni(CO)₄, we report on a [Ni(CO)₄]^.+ salt as the first synthesis of any homoleptic nickel carbonyl cation in the condensed phase. It was prepared by oxidation of nickel metal with the synergistic oxidant Ag[F{Al(OR^F)₃}₂]/0.5 I₂ (R^F=C(CF₃)₃) in CO atmosphere. This D_2d‐symmetric metalloradical represents the last missing entry among the structurally characterized homoleptic carbonyl cations of Groups 6 to 11. Additionally, the nickel tricarbonyl‐nitrosyl cation [Ni(CO)₃(NO)]⁺ was obtained by usage of NO[F{Al(OR^F)₃}₂] and all products were fully characterized by means of IR, Raman, NMR/EPR, single crystal and powder XRD.

Group 6 Hexacarbonyls as Ligands for the Silver Cation: Syntheses, Characterization, and Analysis of the Bonding Compared with the Isoelectronic Group 5 Hexacarbonylates

The syntheses of the two novel complexes [Ag{Mo/W(CO)6 }2 ]+ [F-{Al(ORF )3 }2 ]- (RF =C(CF3 )3 ) are reported along with their structural and spectroscopic characterization. The X-ray structure shows that three carbonyl ligands from each M(CO)6 fragment bend towards the silver atom within binding Ag-C distance range. DFT calculations of the free cations [Ag{M(CO)6 }2 ]+ (M=Cr, Mo, W) in the electronic singlet state give equilibrium structures with C2 symmetry with two bridging carbonyl groups from each hexacarbonyl ligand. Similar structures with C2 symmetry (M=Nb) and D2 symmetry (M=V, Ta) are calculated for the isoelectronic group 5 anions [Ag{M(CO)6 }2 ]- (M=V, Nb, Ta). The electronic structure of the cations is analyzed with the QTAIM and EDA-NOCV methods, which provide detailed information about the nature of the chemical bonds between Ag+ and the {M(CO)6 }2 q (q = -2, M = V, Nb, Ta; q = 0, M = Cr, Mo, W) ligands.

Altering Charges on Heterobimetallic Transition-Metal Carbonyl Clusters

The homoleptic group 5 carbonylates [M(CO)6 ]- (M=Nb, Ta) serve as ligands in carbonyl-terminated heterobimetallic Agm Mn clusters containing 3 to 11 metal atoms. Based on our serendipitous [Ag6 {Nb(CO)6 }4 ]2+ (4 a2+ ) precedent, we established access to such Agm Mn clusters of the composition [Agm {M(CO)6 }n ]x (M=Nb, Ta; m=1, 2, 6; n=2, 3, 4, 5; x=1-, 1+, 2+). Salts of those molecular cluster ions were synthesized by the reaction of [NEt4 ][M(CO)6 ] and Ag[Al(ORF )4 ] (RF =C(CF3 )3 ) in the correct stoichiometry in 1,2,3,4-tetrafluorobenzene at -35 °C. The solid-state structures were determined by single-crystal X-ray diffraction methods and, owing to the thermal instability of the clusters, a limited scope of spectroscopic methods. In addition, DFT-based AIM calculations were performed to provide an understanding of the bonding within these clusters. Apparently, the clusters 3+ (m=6, n=5) and 42+ (m=6, n=4) are superatom complexes with trigonal-prismatic or octahedral Ag6 superatom cores. The [M(CO)6 ]- ions then bind through three CO units as tridentate chelate ligands to the superatom core, giving overall structures related to tetrahedral AX4 (42+ ) or trigonal bipyramidal AX5 molecules (3+ ).

Synthesis and Application of a Perfluorinated Ammoniumyl Radical Cation as a Very Strong Deelectronator

The perfluorinated dihydrophenazine derivative (perfluoro-5,10-bis(perfluorophenyl)-5,10-dihydrophenazine) ("phenazine^F ") can be easily transformed to a stable and weighable radical cation salt by deelectronation (i.e. oxidation) with Ag[Al(OR^F )₄ ]/ Br₂ mixtures (R^F =C(CF₃ )₃ ). As an innocent deelectronator it has a strong and fully reversible half-wave potential versus Fc⁺ /Fc in the coordinating solvent MeCN (E°'=1.21 V), but also in almost non-coordinating oDFB (=1,2-F₂ C₆ H₄ ; E°'=1.29 V). It allows for the deelectronation of [Fe^III Cp*₂ ]⁺ to [Fe^IV (CO)Cp*₂ ]²⁺ and [Fe^IV (CN-^t Bu)Cp*₂ ]²⁺ in common laboratory solvents and is compatible with good σ-donor ligands, such as L=trispyrazolylmethane, to generate novel [M(L)_x ]ⁿ⁺ complex salts from the respective elemental metals.

Stable Salts of Heteroleptic Iron Carbonyl/Nitrosyl Cations

The oxidation of Fe(CO)₅ with the [NO]⁺ salt of the weakly coordinating perfluoroalkoxyaluminate anion [F‐{Al(OR^F)₃}₂]⁻ (R^F=C(CF₃)₃) leads to stable salts of the 18 valence electron (VE) species [Fe(CO)₄(NO)]⁺ and [Fe(CO)(NO)₃]⁺ with the Enemark–Feltham numbers of {FeNO}⁸ and {FeNO}¹⁰. This finally concludes the triad of heteroleptic iron carbonyl/nitrosyl complexes, since the first discovery of the anionic ([Fe(CO)₃(NO)]⁻) and neutral ([Fe(CO)₂(NO)₂]) species over 80 years ago. Both complexes were fully characterized (IR, Raman, NMR, UV/Vis, scXRD, pXRD) and are stable at room temperature under inert conditions over months and may serve as useful starting materials for further investigations.