Molybdenum(VI) Nitrido Complexes with Tripodal Silanolate Ligands. Structure and Electronic Character of an Unsymmetrical Dimolybdenum μ-Nitrido Complex Formed by Incomplete Nitrogen Atom Transfer.

In contrast to a tungsten nitrido complex endowed with a tripodal silanolate ligand framework, which was reported in the literature to be a dimeric species with a metallacyclic core, the corresponding molybdenum nitrides are monomeric entities comprising a regular terminal nitride unit, as proven by single-crystal X-ray diffraction (SC-XRD). Their electronic character is largely determined by the constraints imposed on the metal center by the podand ligand architecture. Mo nuclear magnetic resonance (NMR) and, to a lesser extent, N NMR spectroscopy allow these effects to be studied, which become particularly apparent upon comparison with the spectral data of related molybdenum nitrides comprising unrestrained silanolate, alkoxide, or amide ligands.

Structural characterization and reactivity of a room-temperature-stable, antiaromatic cyclopentadienyl cation salt.

The singlet states of cyclopentadienyl (Cp) cations are considered as true prototypes of an antiaromatic system. Unfortunately, their high intrinsic reactivity inhibited their isolation in the solid state as a salt, and controlled reactions are also scarce. Here we present the synthesis and solid state structure of the room-temperature-stable Cp cation salt [Cp(CF)][SbF].

Reactive high-spin iron(IV)-oxo sites through dioxygen activation in a metal-organic framework.

In nature, nonheme iron enzymes use dioxygen to generate high-spin iron(IV)=O species for a variety of oxygenation reactions. Although synthetic chemists have long sought to mimic this reactivity, the enzyme-like activation of O to form high-spin iron(IV) = O species remains an unrealized goal. Here, we report a metal-organic framework featuring iron(II) sites with a local structure similar to that in α-ketoglutarate-dependent dioxygenases.

Reactivities and Electronic Structures of μ-1,2-Peroxo and μ-1,2-Superoxo CoCo Complexes: Electrophilic Reactivity and O Release Induced by Oxidation.

Peroxo complexes are key intermediates in water oxidation catalysis (WOC). Cobalt plays an important role in WOC, either as oxides CoO or as {Co(μ1,2-peroxo)Co} complexes, which are the oldest peroxo complexes known. The oxidation of {Co(μ1,2-peroxo)Co} complexes had usually been described to form {Co(μ1,2-superoxo)Co} complexes; however, recently the formation of {Co(μ1,2-peroxo)Co} species were suggested.

Synthesis and isolation of a triplet bismuthinidene with a quenched magnetic response.

Large spin-orbit coupling (SOC) is an intrinsic property of the heavy elements that directly affects the electronic structures of the compounds. In this work, we report the synthesis and characterization of a monocoordinate bismuthinidene that features a rigid and bulky ligand. All magnetic measurements [superconducting quantum interference device (SQUID), nuclear magnetic resonance (NMR)] point to a diamagnetic compound.

Spectroscopic and Magnetic Studies of Co(II) Scorpionate Complexes: Is There a Halide Effect on Magnetic Anisotropy?

The observation of single-molecule magnetism in transition-metal complexes relies on the phenomenon of zero-field splitting (ZFS), which arises from the interplay of spin-orbit coupling (SOC) with ligand-field-induced symmetry lowering. Previous studies have demonstrated that the magnitude of ZFS in complexes with 3d metal ions is sometimes enhanced through coordination with heavy halide ligands (Br and I) that possess large free-atom SOC constants. In this study, we systematically probe this "heavy-atom effect" in high-spin cobalt(II)-halide complexes supported by substituted hydrotris(pyrazol-1-yl)borate ligands (Tp and Tp).

Self-Assembled Encapsulation of CuX (X = Br, Cl) in a Gold Phosphine Box-like Cavity with Metallophilic Au-Cu Interactions.

Synthetic routes to the crystallization of two new box-like complexes, [Au(Triphos)(CuBr)](OTf)·(CHCl)·(CHOH)·(HO) () and [Au(Triphos) (CuCl)](PF)·(CHCl) () (triphos = bis(2-diphenylphosphinoethyl)phenylphosphine), have been developed. The two centrosymmetric cationic complexes have been structurally characterized through single-crystal X-ray diffraction and shown to contain a CuX (X = Br or Cl) unit suspended between two Au(I) centers without the involvement of bridging ligands. These colorless crystals display green luminescence (λ = 527 nm) for () and teal luminescence (λ = 464 nm) for ().

Synthesis, Isolation, and Characterization of Two Cationic Organobismuth(II) Pincer Complexes Relevant in Radical Redox Chemistry.

Herein, we report the synthesis, isolation, and characterization of two cationic organobismuth(II) compounds bearing N,C,N pincer frameworks, which model crucial intermediates in bismuth radical processes. X-ray crystallography uncovered a monomeric Bi(II) structure, while SQUID magnetometry in combination with NMR and EPR spectroscopy provides evidence for a paramagnetic = 1/2 state. High-resolution multifrequency EPR at the X-, Q-, and W-band enable the precise assignment of the full - and Bi -tensors.

Postsynthetic Treatment of ZIF-67 with 5-Methyltetrazole: Evolution from Pseudo-T to Pseudo-O Symmetry and Collapse of Magnetic Ordering.

Reaction of Co(II) nitrate with 2-methylimidazole (2mIm) yields ZIF-67, the structure of which features Co(II) ions in pseudo-tetrahedral coordination geometry. Strong antiferromagnetic interactions between Co(II) ions mediated by the 2mIm ligands lead to antiferromagnetic ordering at 22 K. Postsynthetic treatment of Co(II) ZIF-67 with 5-methyltetrazole (5mT) results in the loss of crystallinity and magnetic order.

Antiferromagnetic Exchange and Metal-Metal Bonding in Roussin's Black Sulfur and Selenium Salts.

Atom-efficient syntheses of the tetraethylammonium Roussin black sulfur and selenium salts ((EtN)[FeE(NO)], E = S, Se) as well as their N-labeled counterparts are described herein. Broken-symmetry DFT calculations were conducted on both complexes to model an antiferromagnetic interaction between the apical {FeNO} unit, = 3/2, and the three basal {Fe(NO)} units, = 1/2. The calculated values are -1813 and -1467 cm for the sulfur and selenium compounds, respectively.

Tetrairon(II) extended metal atom chains as single-molecule magnets.

Iron-based extended metal atom chains (EMACs) are potentially high-spin molecules with axial magnetic anisotropy and thus candidate single-molecule magnets (SMMs). We herein compare the tetrairon(ii), halide-capped complexes [Fe4(tpda)3Cl2] (1Cl) and [Fe4(tpda)3Br2] (1Br), obtained by reacting iron(ii) dihalides with [Fe2(Mes)4] and N2,N6-di(pyridin-2-yl)pyridine-2,6-diamine (H2tpda) in toluene, under strictly anhydrous and anaerobic conditions (HMes = mesitylene). Detailed structural, electrochemical and Mössbauer data are presented along with direct-current (DC) and alternating-current (AC) magnetic characterizations.

Probing the Magnetic Anisotropy of Co(II) Complexes Featuring Redox-Active Ligands.

Coordination complexes that possess large magnetic anisotropy (otherwise known as zero-field splitting, ZFS) have possible applications in the field of magnetic materials, including single molecule magnets (SMMs). Previous studies have explored the role of coordination number and geometry in controlling the magnetic anisotropy and SMM behavior of high-spin ( = 3/2) Co(II) complexes. Building upon these efforts, the present work examines the impact of ligand oxidation state and structural distortions on the spin states and ZFS parameters of pentacoordinate Co(II) complexes.

Heterometallic Precursor with 2:2:1 Metal Ratio Requiring at Least a Pentanuclear Molecular Assembly.

This work represents an important step in the quest to make heterometallic molecules featuring specific metal types and complicated metal ratios. The rational design, synthesis, and characterization of a complex heterometallic single-source molecular precursor for the next generation sodium-ion battery cathode material, NaMnFeO, is described. A unique pentametallic platform [Mn(ptac)-Na-Mn(acac)-Na-Mn(ptac)] () was derived from the known polymeric structure of [NaMn(acac)], through a series of elaborate design procedures, such as mixed-ligand, unsymmetric ligand, and mixed-valent approaches.

From Pincer to Paddlewheel: C-H and C-S Bond Activation at Bis(2-pyridylthio)methane by Palladium(II).

The bis(2-pyridylthio)methanidopalladium(II) pincer complex (1), containing a Pd-C bond, was obtained from the reaction of bis(2-pyridylthio)methane (HL) with palladium(II) acetate in toluene under reflux. When palladium(II) trifluoroacetate was used, HL reacted to generate the tetrakis(pyridine-2-thiol)palladium(II) complex (2). Complex 2 was converted to a heterobimetallic palladium(II)-iron(II) paddlewheel complex (3) upon treatment with iron(II) triflate in the presence of a base in acetonitrile at room temperature.

Direct Observation of Node-to-Node Communication in Zeolitic Imidazolate Frameworks.

Zeolitic imidazolate frameworks (ZIFs) with open-shell transition metal nodes represent a promising class of highly ordered light harvesting antennas for photoenergy applications. However, their charge transport properties within the framework, the key criterion to achieve efficient photoenergy conversion, are not yet explored. Herein, we report the first direct evidence of a charge transport pathway through node-to-node communication in both ground state and excited state ZIFs using the combination of paramagnetic susceptibility measurements and time-resolved optical and X-ray absorption spectroscopy.