CO Oxidation by Group 3 Metal Monoxide Cations Supported on [Fe(CO)4]2−

Infrared photodissociation spectroscopy of mass‐selected heteronuclear cluster anions in the form of OMFe(CO)₅⁻ (M=Sc, Y, La) indicates that all these anions involve an 18‐electron [Fe(CO)₄]²⁻ building block that is bonded with the M center through two bridged carbonyl ligands. The OLaFe(CO)₅⁻ anion is determined to be a CO‐tagged complex involving a [Fe(CO)₄]²⁻[LaO]⁺ anion core. In contrast, the OYFe(CO)₅⁻ anion is characterized to have a [Fe(CO)₄]²⁻[Y(η²‐CO₂)]⁺ structure involving a side‐on bonded CO₂ ligand. The CO‐tagged complex and the [Fe(CO)₄]²⁻[Sc(η²‐CO₂)]⁺ isomer co‐exist for the OScFe(CO)₅⁻ anion. These observations indicate that both the ScO⁺ and YO⁺ cations supported on [Fe(CO)₄]²⁻ are able to oxidize CO to CO₂. Theoretical analyses show that [Fe(CO)₄]²⁻ coordination significantly weakens the MO⁺ bond and decreases the energy gap of the interacting valence orbitals between MO⁺ and CO, leading to the CO oxidation reactions being both thermodynamically exothermic and kinetically facile.     

Preparation and Characterization of Uranium–Iron Triple‐Bonded UFe(CO)3− and OUFe(CO)3− Complexes

We report the preparation of UFe(CO)₃⁻ and OUFe(CO)₃⁻ complexes using a laser‐vaporization supersonic ion source in the gas phase. These compounds were mass‐selected and characterized by infrared photodissociation spectroscopy and state‐of‐the‐art quantum chemical studies. There are unprecedented triple bonds between U 6d/5f and Fe 3d orbitals, featuring one covalent σ bond and two Fe‐to‐U dative π bonds in both complexes. The uranium and iron elements are found to exist in unique formal U(I or III) and Fe(−II) oxidation states, respectively. These findings suggest that there may exist a whole family of stable df–d multiple‐bonded f‐element‐transition‐metal compounds that have not been fully recognized to date.     

The Formation of High‐Order Polybromides in a Room‐Temperature Ionic Liquid: From Monoanions ([Br5]− to [Br11]−) to the Isolation of [PC16H36]2[Br24] as Determined by van der Waals Bonding Radii

An unprecedented diversity of high‐order bromine catenates (anionic polybromides) was generated in a tetraalkylphosphonium‐based room temperature ionic liquid system. Raman spectroscopy was used to identify polybromide monoanions ranging from [Br₅]^? to [Br₁₁]^? in the bulk solution, while single‐crystal X‐ray diffraction identified extended networks of linked [Br₁₁]^? units, forming a previously unknown polymeric [Br₂₄]^2? dianion. This represents the largest polybromide species identified to date. In combination with recent work, this suggests that other, higher order molecular polybromide ions might be isolated.     

Charged Si9 Clusters in Neat Solids and the Detection of [H2Si9]2− in Solution: A Combined NMR,Raman, Mass Spectrometric,and Quantum Chemical Investigation

Polyanionic silicon clusters are provided by the Zintl phases K₄Si₄, comprising [Si₄]⁴⁻ units, and K₁₂Si₁₇, consisting of [Si₄]⁴⁻ and [Si₉]⁴⁻ clusters. A combination of solid‐state MAS‐NMR, solution NMR, and Raman spectroscopy, electrospray ionization mass spectrometry, and quantum‐chemical investigations was used to investigate four‐ and nine‐atomic silicon Zintl clusters in neat solids and solution. The results were compared to ²⁹Si isotope‐enriched samples. ²⁹Si‐MAS NMR and Raman shifts of the phase‐pure solids K₄Si₄ and K₁₂Si₁₇ were interpreted by quantum‐chemical calculations. Extraction of [Si₉]⁴⁻ clusters from K₁₂Si₁₇ with liquid ammonia/222crypt and their transfer to pyridine yields in a red solid containing Si₉ clusters. This compound was characterized by elemental and EDX analyses and ²⁹Si‐MAS NMR and Raman spectroscopy. Charged Si₉ clusters were detected by ²⁹Si NMR in solution. ²⁹Si and ¹H NMR spectra reveal the presence of the [H₂Si₉]²⁻ cluster anion in solution.