High-Spin Iron(VI), Low-Spin Ruthenium(VI), and Magnetically Bistable Osmium(VI) in Molecular Group 8 Nitrido Trifluorides NMF3.

Pseudo-tetrahedral nitrido trifluorides N≡MF3 (M=Fe, Ru, Os) and square pyramidal nitrido tetrafluorides N≡MF4 (M=Ru, Os) were formed by free-metal-atom reactions with NF3 and subsequently isolated in solid neon at 5 K. Their IR spectra were recorded and analyzed aided by quantum-chemical calculations. For a d2 electron configuration of the N≡MF3 compounds in C3v symmetry, Hund's rule predict a high-spin 3 A2 ground state with two parallel spin electrons and two degenerate metal d(δ)-orbitals. The corresponding high-spin 3 A2 ground state was, however, only found for N≡FeF3 , the first experimentally verified neutral nitrido FeVI species. The valence-isoelectronic N≡RuF3 and N≡OsF3 adopt different angular distorted singlet structures. For N≡RuF3 , the triplet 3 A2 state is only 5 kJ mol-1 higher in energy than the singlet 1 A' ground state, and the magnetically bistable molecular N≡OsF3 with two distorted near degenerate 1 A' and 3 A" electronic states were experimentally detected at 5 K in solid neon.

A Cornucopia of Iridium Nitrogen Compounds Produced from Laser-Ablated Iridium Atoms and Dinitrogen.

The reaction of laser-ablated iridium atoms with dinitrogen molecules and nitrogen atoms yield several neutral and ionic iridium dinitrogen complexes such as Ir(N2 ), Ir(N2 )+ , Ir(N2 )2 , Ir(N2 )2 - , IrNNIr, as well as the nitrido complexes IrN, Ir(N)2 and IrIrN. These reaction products were deposited in solid neon, argon and nitrogen matrices and characterized by their infrared spectra. Assignments of vibrational bands are supported by ab initio and first principle calculations as well as 14/15 N isotope substitution experiments. The structural and electronic properties of the new dinitrogen and nitrido iridium complexes are discussed. While the formation of the elusive dinitrido complex Ir(N)2 was observed in a subsequent reaction of IrN with N atoms within the cryogenic solid matrices, the threefold coordinated iridium trinitride Ir(N)3 could not be observed so far.

Fluoro Nitrenoid Complexes FN=MF2 (M=Co, Rh, Ir): Electronic Structure Dichotomy and Formation of Nitrido Fluorides N≡MF3.

The fluoronitrenoid metal complexes FNCoF2 and FNRhF2 as well as the first ternary RhVI and IrVI complexes NIrF3 and NRhF3 are described. They were obtained by the reaction of excited Group-9 metal atoms with NF3 and their IR spectra, isolated in solid rare gases (neon and argon), were recorded. Aided by the observed 14/15 N isotope shifts and quantum-chemical predictions, all four stretching fundamentals of the novel complexes were safely assigned. The F-N stretching frequencies of the fluoronitrenoid complexes FNCoF2 (1056.8 cm-1 ) and FNRhF2 (872.6 cm-1 ) are very different and their N-M bonds vary greatly. In FNCoF2 , the FN ligand is singly bonded to Co and bears considerable iminyl/nitrene radical character, while the N-Rh bond in FNRhF2 is a strong double bond with comparatively strong σ- and π-bonds. The anticipated rearrangement of FNCoF2 to the nitrido CoVI complex is predicted to be endothermic and was not observed.

Beyond Oxides: Nitride as a Ligand in a Neutral IrIX NO3 Molecule Bearing a Transition Metal at High Oxidation State.

Theoretical calculations utilizing relativistic ZORA Hamiltonian point to the conceivable existence of an IrNO3 molecule in C3v geometry. This minimum is shown to correspond to genuine nonavalent iridium nitride trioxide, which is a neutral analogue of cationic [IrO4 ]+ species detected recently. Despite the presence of nitride anion, the molecule is protected by substantial barriers exceeding 200 kJ mol-1 against transformations leading, for example, to global minimum (O=)2 Ir-NO, which contains metal at a lower formal oxidation state.

Synthesis of an All-Ferric Cuboidal Iron-Sulfur Cluster [FeIII4 S4 (SAr)4 ].

An unprecedented, super oxidized all-ferric iron-sulfur cubanoid cluster with all terminal thiolates, Fe4 S4 (STbt)4 (3) [Tbt=2,4,6-tris{bis(trimethylsilyl)methyl}phenyl], has been isolated from the reaction of the bis-thiolate complex Fe(STbt)2 (2) with elemental sulfur. This cluster 3 has been characterized by X-ray crystallography, zero-field 57 Fe Mössbauer spectroscopy, cyclic voltammetry, and other relevant physico-chemical methods. Based on all the data, the electronic ground state of the cluster has been assigned to be Stot =0.

Valence Interconversion of Octahedral Nickel(II/III/IV) Centers.

Three oxidation states (+2, +3, +4) of an octahedral nickel center were stabilized in a newly prepared RhNiRh trinuclear complex, [Ni{Rh(apt)3 }2 ]n+ (apt=3- aminopropanethiolate), in which the nickel center was bound by six thiolato donors sourced from two redox-inert fac-[RhIII (apt)3 ] octahedral units. The three oxidation states of the octahedral nickel center were fully characterized by single-crystal X-ray crystallography, as well as spectroscopic, electrochemical, and magnetic measurements; all three were interconvertible, and the conversion was accompanied by changes in color, magnetism, and Jahn-Teller distortion.

Extending the Row of Lanthanide Tetrafluorides: A Combined Matrix-Isolation and Quantum-Chemical Study.

Only the neutral tetrafluorides of Ce, Pr, and Tb as well as the [LnF7 ](3-) anions of Dy and Nd, with the metal in the +IV oxidation state, have been previously reported. We report our attempts to extend the row of neutral lanthanide tetrafluorides through the reaction of laser-ablated metal atoms with fluorine and their stabilization and characterization by matrix-isolation IR spectroscopy. In addition to the above three tetrafluorides, we found two new tetrafluorides, (3) NdF4 and (7) DyF4 , both of which are in the +IV oxidation state, which extends this lanthanide oxidation state to two new metals. Our experimental results are supported by quantum-chemical calculations and the role of the lanthanide oxidation state is discussed for both the LnF4 and [LnF4 ](-) species. Most of the LnF4 species are predicted to be in the +IV oxidation state and all of the [LnF4 ](-) anions are predicted to be in the +III oxidation state. The LnF4 species are predicted to be strong oxidizing agents and the LnF3 species are predicted to be moderate to strong Lewis acids.

Dispersion Forces, Disproportionation, and Stable High-Valent Late Transition Metal Alkyls.

The transition metal tetra- and trinorbornyl bromide complexes, M(nor)4 (M=Fe, Co, Ni) and Ni(nor)3 Br (nor=1-bicyclo[2.2.1]hept-1-yl) and their homolytic fragmentations were studied computationally using hybrid density functional theory (DFT) at the B3PW91 and B3PW91-D3 dispersion-corrected levels. Experimental structures were well replicated; the dispersion correction resulted in shortened M-C bond lengths for the stable complexes, and it was found that Fe(nor)4 receives a remarkable 45.9 kcal mol-1 stabilization from the dispersion effects whereas the tetragonalized Co(nor)4 shows stabilization of 38.3 kcal mol-1 . Ni(nor)4 was calculated to be highly tetragonalized with long Ni-C bonds, providing a rationale for its current synthetic inaccessibility. Isodesmic exchange evaluation for Fe(nor)4 confirmed that dispersion force attraction between norbornyl substituents is fundamental to the stability of these species.

Polyfluorides and Neat Fluorine as Host Material in Matrix-Isolation Experiments.

The use of neat fluorine in matrix isolation is reported, as well as the formation of polyfluoride monoanions under cryogenic conditions. Purification procedures and spectroscopic data of fluorine are described, and matrix shifts of selected molecules and impurities in solid fluorine are compared to those of common matrix gases (Ar, Kr, N2 , Ne). The reaction of neat fluorine and IR-laser ablated metal atoms to yield fluorides of chromium (CrF5 ), palladium (PdF2 ), gold (AuF5 ), and praseodymium (PrF4 ) has been investigated. The fluorides have been characterized in solid fluorine by IR spectroscopy at 5 K. Also the fluorination of Kr and the photo-dismutation of XeO4 have been studied by using IR spectroscopy in neat fluorine. Formation of the [F5 ](-) ion was obtained by IR-laser ablation of platinum in the presence of fluorine and proven in a Ne matrix at 5 K by two characteristic vibrational bands of [F5 ](-) at $\tilde \nu $=850.7 and 1805.0 cm(-1) and its photo-behavior.

Organonickel(IV) chemistry: a new catalyst?

With scorpionate ligands finding their way into organonickel chemistry, the state of the art of present-day nickel(IV) chemistry is highlighted. Will rapid CX coupling reactions emerge as a domain of higher-oxidation-state nickel chemistry?

Spectral investigation of phthalocyanine complexes of high-valence silver and their aggregates.

Several novel silver(II) complexes ligating a tetra-substituted phthalocyaninate, [Ag(tbpc)] (where tbpc denotes tetra-tert-butylphthalocyaninate), [Ag(tppc)] (tppc = tetrakis(2,6-dimethylphenoxy)phthalocyaninate), [Ag(tObpc)] (tObpc = tetra-n-butoxyphthalocyaninate), and [Ag(tpySpc)] (tpySpc = tetrakis(4-pyridylthio)phthalocyaninate) have been synthesized and characterized by elemental analyses, MALDI-TOF MS, optical absorption, and magnetic circular dichroism (MCD) spectroscopy. Although all the compounds are well soluble in common organic solvents, concentration studies on their optical spectra in solutions have found that they are prone to strongly aggregate in a cofacial manner (i.e., H-aggregate). Silver(II) complexes, which are essentially non-fluorescent, are readily demetallated in the presence of appropriate reductant (e.g., I- or BH4-) to liberate the corresponding macrocyclic ligand, which emits intense red fluorescence. Chemical oxidation by using NOBF4 generates the corresponding silver(III) species.