An Anti CuO2‐type Metal Hydride Square Net Structure in Ln2M2As2Hx (Ln=La or Sm,M=Ti,V, Cr,or Mn)

Using a high pressure technique and the strong donating nature of H⁻, a new series of tetragonal La₂Fe₂Se₂O₃‐type layered mixed‐anion arsenides, Ln₂M₂As₂H_x, was synthesized (Ln=La or Sm, M=Ti, V, Cr, or Mn; x≈3). In these compounds, an unusual M₂H square net, which has anti CuO₂ square net structures accompanying two As³⁻ ions, is sandwiched by (LaH)₂ fluorite layers. Notably, strong metal–metal bonding with a distance of 2.80 Å was confirmed in La₂Ti₂As₂H_2.3, which has metallic properties. In fact, these compounds are situated near the boundary between salt‐like ionic hydrides and transition‐metal hydrides with metallic characters.     

β‐Diketiminate‐Stabilized Magnesium(I) Dimers and Magnesium(II) Hydride Complexes: Synthesis,Characterization, Adduct Formation,and Reactivity Studies

The preparation and characterization of a series of magnesium(II) iodide complexes incorporating β‐diketiminate ligands of varying steric bulk and denticity, namely, [(ArNCMe)₂CH]^? (Ar=phenyl, (^PhNacnac), mesityl (^MesNacnac), or 2,6‐diisopropylphenyl (Dipp, ^DippNacnac)), [(DippNCtBu)₂CH]^? (^tBuNacnac), and [(DippNCMe)(Me₂NCH₂CH₂NCMe)CH]^? (^DmedaNacnac) are reported. The complexes [(^PhNacnac)MgI(OEt₂)], [(^MesNacnac)MgI(OEt₂)], [(^DmedaNacnac)MgI(OEt₂)], [(^MesNacnac)MgI(thf)], [(^DippNacnac)MgI(thf)], [(^tBuNacnac)MgI], and [(^tBuNacnac)MgI(DMAP)] (DMAP=4‐dimethylaminopyridine) were shown to be monomeric by X‐ray crystallography. In addition, the related β‐diketiminato beryllium and calcium iodide complexes, [(^MesNacnac)BeI] and [{(^DippNacnac)CaI(OEt₂)}₂] were prepared and crystallographically characterized. The reductions of all metal(II) iodide complexes by using various reagents were attempted. In two cases these reactions led to the magnesium(I) dimers, [(^MesNacnac)MgMg(^MesNacnac)] and [(^tBuNacnac)MgMg(^tBuNacnac)]. The reduction of a 1:1 mixture of [(^DippNacnac)MgI(OEt₂)] and [(^MesNacnac)MgI(OEt₂)] with potassium gave a low yield of the crystallographically characterized complex [(^DippNacnac)Mg(μ‐H)(μ‐I)Mg(^MesNacnac)]. All attempts to form beryllium(I) or calcium(I) dimers by reductions of [(^MesNacnac)BeI], [{(^DippNacnac)CaI(OEt₂)}₂], or [{(^tBuNacnac)CaI(thf)}₂] have so far been unsuccessful. The further reactivity of the magnesium(I) complexes [(^MesNacnac)MgMg(^MesNacnac)] and [(^tBuNacnac)MgMg(^tBuNacnac)] towards a variety of Lewis bases and unsaturated organic substrates was explored. These studies led to the complexes [(^MesNacnac)Mg(L)Mg(L)(^MesNacnac)] (L=THF or DMAP), [(^MesNacnac)Mg(μ‐AdN₆Ad)Mg(^MesNacnac)] (Ad=1‐adamantyl), [(^tBuNacnac)Mg(μ‐AdN₆Ad)Mg(^tBuNacnac)], and [(^MesNacnac)Mg(μ‐tBu₂N₂C₂O₂)Mg(^MesNacnac)] and revealed that, in general, the reactivity of the magnesium(I) dimers is inversely proportional to their steric bulk. The preparation and characterization of [(^tBuNacnac)Mg(μ‐H)₂Mg(^tBuNacnac)] has shown the compound to have different structural and physical properties to [(^tBuNacnac)MgMg(^tBuNacnac)]. Treatment of the former with DMAP has given [(^tBuNacnac)Mg(H)(DMAP)], the X‐ray crystal structure of which disclosed it to be the first structurally authenticated terminal magnesium hydride complex. Although attempts to prepare [(^MesNacnac)Mg(μ‐H)₂Mg(^MesNacnac)] were not successful, a neutron diffraction study of the corresponding magnesium(I) complex, [(^MesNacnac)MgMg(^MesNacnac)] confirmed that the compound is devoid of hydride ligands.     

MnTaO2N: Polar LiNbO3‐type Oxynitride with a Helical Spin Order

The synthesis, structure, and magnetic properties of a polar and magnetic oxynitride MnTaO₂N are reported. High‐pressure synthesis at 6 GPa and 1400 °C allows for the stabilization of a high‐density structure containing middle‐to‐late transition metals. Synchrotron X‐ray and neutron diffraction studies revealed that MnTaO₂N adopts the LiNbO₃‐type structure, with a random distribution of O^2? and N^3? anions. MnTaO₂N with an “orbital‐inactive” Mn²⁺ ion (d⁵; S=5/2) exhibits a nontrivial helical spin order at 25 K with a propagation vector of [0,0,δ] (δ≈0.3), which is different from the conventional G‐type order observed in other orbital‐inactive perovskite oxides and LiNbO₃‐type oxides. This result suggests the presence of strong frustration because of the heavily tilted MnO₄N₂ octahedral network combined with the mixed O^2?/N^3? species that results in a distribution of (super)‐superexchange interactions.     

Luminescent Heteropolynuclear Complexes of 3,5‐Dimethylpyrazolate [Pt2Au2M2(Me2pz)8] (M=Ag,Cu) Showing the Synergistic Effect of Three Transition Elements in the Excited State

Swap the coins! The Pt₂Au₂, Pt₂Au₂Cu₂, and Pt₂Au₂Ag₂ complexes of 3,5‐dimethylpyrazolate exhibit yellow‐green, orange, and sky‐blue luminescence, respectively (see figure). The emission energies of Pt₂Au₂M₂ complexes can be controlled by the change of the third coinage metal ions M. The Pt₂Au₂M₂ complexes take the cis configuration with respect to the Au₂M₂ plane.

     

Reactions of Hydrated Singly Charged First‐Row Transition‐Metal Ions M+(H2O)n (M=V,Cr, Mn,Fe, Co,Ni, Cu,and Zn) toward Nitric Oxide in the Gas Phase

Reactions of M⁺(H₂O)_n (M=V, Cr, Mn, Fe, Co, Ni, Cu, Zn; n≤40) with NO were studied by Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometry. Uptake of NO was observed for M=Cr, Fe, Co, Ni, Zn. The number of NO molecules taken up depends on the metal ion. For iron and zinc, NO uptake is followed by elimination of HNO and formation of the hydrated metal hydroxide, with strong size dependence. For manganese, only small HMnOH⁺(H₂O)_n?1 species, which are formed under the influence of room‐temperature black‐body radiation, react with NO. Here NO uptake competes with HNO formation, both being primary reactions. The results illustrate that, in the presence of water, transition‐metal ions are able to undergo quite particular and diverse reactions with NO. HNO is presumably formed through recombination of a proton and ³NO^? for M=Fe, Zn, preferentially for n=15–20. For manganese, the hydride in HMnOH⁺(H₂O)_n?1 is involved in HNO formation, preferentially for n≤4. The strong size dependence of the HNO formation efficiency illustrates that each molecule counts in the reactions of small ionic water clusters.     

Metal Chelates of N‐(2‐pyridylmethyl)iminodiacetate(2‐) Ion (pmda). Part II. Ternary pmda Chelates with M = Co,Cu or Zn and Creatinine as Auxiliary Ligand

The compounds [Cu(pmda)(crea)]·H₂O ( 1 ), [Zn(pmda)(crea)]·H₂O ( 2 ) and [Co(pmda)(crea)(H₂O)]·H₂O ( 3 ) were prepared and characterized by thermal, spectral and X‐ray diffraction methods. In compounds 1 and 2 the M^II coordination is of type 4+1 and approaches to a trigonal bipyramid (71.85 and 86.18 %, respectively) with rather linear N(pmda)‐M^II‐N(crea) trans‐apical angles, but with different longest coordination bond (Cu‐O(pmda) or Zn‐N(apliphatic, pmda), respectively). Both compounds are isotypic and one intra‐molecular interligand N‐H···O interaction reinforces the molecular recogniton crea‐M^II(pmda) chelate. In contrast, the compound 3 exhibits an octahedral coordination, imposed by the 3d⁷ electronic configuration of the cobalt(II) atom, and the crea‐chelate recognition involves the Co‐N(crea) coordination bond and one intramolecular ‘bifurcated’ H‐bonding interaction between one N‐H(crea) bond and one O(pmda) plus the O(aqua) atoms as ‘acceptors’.