Formation and Characterization of the Boron Dicarbonyl Complex [B(CO)2]−

We report the synthesis and spectroscopic characterization of the boron dicarbonyl complex [B(CO)₂]^?. The bonding situation is analyzed and compared with the aluminum homologue [Al(CO)₂]^? using state‐of‐the‐art quantum chemical methods.     

PtOxCly(OH)z(H2O)n Complexes under Oxidative and Reductive Conditions: Impact of the Level of Theory on Thermodynamic Stabilities

Platinum-based catalysts with Cl⁻, OH⁻, O²⁻ and H₂O ligands, are involved in many industrial processes. Their final chemical properties are impacted by calcination and reduction applied during the preparation and activation steps. We investigate their stability under these reactive conditions with density functional theory (DFT). We benchmark various functionals (PBE-dDsC, optPBE, B3LYP, HSE06, PBE0, TPSS, RTPSS and SCAN) against ACFDT-RPA. PBE-dDsC is well adapted, although hybrid functionals are more accurate for redox reactions. Thermodynamic phase diagrams are determined by computing the chemical potential of the species as a function of temperature and partial pressures of H₂O, HCl, O₂ and H₂. The stability and nature of the Pt species are highly sensitive to the activation conditions. Under O₂, high temperatures favour PtO₂ while under H₂, platinum is easily reduced to Pt(0). Chlorine modifies the coordination sphere of platinum during calcination by stabilizing PtCl₄ and shifts the reduction of platinum to higher temperatures under H₂.     

D∞h B2(BS)2−/2− and Td B(BS)4−: Boron sulfide clusters containing BB multiple bonds and B− tetrahedral centers

A density functional theory investigation on the geometrical and electronic properties of B₄S (B₂(BS)) and B₅S (B(BS)) clusters has been performed in this work. Both the doublet B₂(BS) ([S?B? BB? B?S]^?) (D_∞h, ²Π_u) and the singlet B₂(BS) ([S?B? B?B? B?S]^2?) (D_∞h, ¹Σ) proved to have perfect linear ground‐state structures containing a multiply bonded BB core (BB or B?B) terminated with two BS groups, while T_d B(BS) turned out to possess a perfect B^? tetrahedral center directly corrected to four BS groups, similar to the corresponding boron hydride molecules of D_∞h B₂H, D_∞h B₂H, and T_d BH, respectively. B₄S₂ and B₅S₄ neutrals, however, appeared to be much different: they favor a planar fan‐shaped C_2v B₄S₂ (a di‐S‐bridged B₄ rhombus) and a planar kite‐like C_2v B₅S₄ (a di‐S‐bridged B₃ triangle bonded to two BS groups), respectively. One‐electron detachment energies and symmetrical stretching vibrational frequencies are calculated for D_∞h B₂(BS) and T_d B(BS) monoanions to facilitate their future characterizations. Neutral salts of B₂(BS)₂Li₂ with an elusive B?B triple bond and B(BS)₄Li containing a tetrahedral B^? center are predicted possible to be targeted in experiments. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Co‐Adsorption of O2 and CO on Au2−: Infrared Photodissociation Spectroscopy and Theoretical Study of [Au2O2(CO)n]− (n=2–6)

The co‐adsorption of O₂ and CO on anionic sites of gold species is considered as a crucial step in the catalytic CO oxidation on gold catalysts. In this regard, the [Au₂O₂(CO)_n]^? (n=2–6) complexes were prepared by using a laser vaporization supersonic ion source and were studied by using infrared photodissociation spectroscopy in the gas phase. All the [Au₂O₂(CO)_n]^? (n=2–6) complexes were characterized to have a core structure involving one CO and one O₂ molecule co‐adsorbed on Au₂^? with the other CO molecules physically tagged around. The CO stretching frequency of the [Au₂O₂(CO)]^? core ion is observed around =2032–2042 cm^?1, which is about 200 cm^?1 higher than that in [Au₂(CO)₂]^?. This frequency difference and the analyses based on density functional calculations provide direct evidence for the synergy effect of the chemically adsorbed O₂ and CO. The low lying structures with carbonate group were not observed experimentally because of high formation barriers. The structures and the stability (i.e., the inertness in a sense) of the co‐adsorbed O₂ and CO on Au₂^? may have relevance to the elementary reaction steps on real gold catalysts.     

Towards Polysulfuric Acids: The Hydrogentrisulfate Anion [HS3O10]− in A[HS3O10] (A=Na,K, Rb)

The reaction of Na₂SO₄ and K₂SO₄ with fuming sulfuric acid (65 % SO₃) yielded colorless extremely sensitive crystals of Na[HS₃O₁₀] (monoclinic; P2₁/n (No. 14); Z=4; a=707.36(2), b=1378.56(4), c=848.10(3) pm; β=94.817(1)°; V=824.09(4) ? 10⁶ pm³) and K[HS₃O₁₀] (orthorhombic; Pccn (No. 56); Z=4; a=1057.16(3), b=807.81(2), c=897.57(2) pm; V=766.51(3) ? 10⁶ pm³). The analogous rubidium compound Rb[HS₃O₁₀] (orthorhombic; Pnma (No. 62); Z=4; a=891.43(3), b=1095.34(4), c=839.37(3) pm; V=819.58(5) ? 10⁶ pm³) originates from the reaction of Rb₂CO₃ and SO₃. All of the different structures contain the hitherto unknown anion [HS₃O₁₀]^? and are stamped by strong hydrogen bonds linking the anions either to dimers or chains. Theoretical investigations by DFT methods give further insight in the structural characteristics of [HS₃O₁₀]^?. The preparation of the [HS₃O₁₀]^? anion can be seen as an important milestone on our way to the still elusive polysulfuric acids.     

Unravelling Local Atomic Order of the Anionic Sublattice in M(Al1−xGax)4 with M=Sr and Ba by Using NMR Spectroscopy and Quantum Mechanical Modelling

The quasibinary section of the intermetallic phases MAl₄ and MGa₄ with M=Sr and Ba have been characterised by means of X‐ray diffraction (XRD) studies and differential thermal analysis. The binary phases show complete miscibility and form solid solutions M(Al_1?xGa_x)₄ with M=Sr and Ba. These structures crystallise in the BaAl₄ structure type with four‐ and five‐bonded Al and/or Ga atoms (denoted as Al(4b), Al(5b), Ga(4b), and Ga(5b), respectively) that form a polyanionic Al/Ga sublattice. Solid state ²⁷Al NMR spectroscopic analysis and quantum mechanical (QM) calculations were applied to study the bonding of the Al centres and the influence of Al/Ga substitution, especially in the regimes with low degrees of substitution. M(Al_1?xGa_x)₄ with M=Sr and Ba and 0.925≤x≤0.975 can be described as a matrix of the binary majority compound in which a low amount of the Ga atoms has been substituted by Al atoms. In good agreement with the QM calculations, ²⁷Al NMR investigations and single crystal XRD studies prove a preferred occupancy of Al(4b) for these substitution regimes. Furthermore, two different local Al environments were found, namely isolated Al(4b1) atoms and Al(4b2), due to the formation of Al(4b)–Al(4b) pairs besides isolated Al(4b) atoms within the polyanionic sublattice. QM calculations of the electric field gradient (EFG) using superlattice structures under periodic boundary conditions are in good agreement with the NMR spectroscopic results.     

A Dual Plating Battery with the Iodine/[ZnIx(OH2)4−x]2−x Cathode

Plating battery electrodes typically deliver higher specific capacity values than insertion or conversion electrodes because the ion charge carriers represent the sole electrode active mass, and a host electrode is unnecessary. However, reversible plating electrodes are rare for electronically insulating nonmetals. Now, a highly reversible iodine plating cathode is presented that operates on the redox couples of I₂/[ZnI_x(OH₂)_4?x]^2?x in a water‐in‐salt electrolyte. The iodine plating cathode with the theoretical capacity of 211 mAh g^?1 plates on carbon fiber paper as the current collector, delivering a large areal capacity of 4 mAh cm^?2. Tunable femtosecond stimulated Raman spectroscopy coupled with DFT calculations elucidate a series of [ZnI_x(OH₂)_4?x]^2?x superhalide ions serving as iodide vehicles in the electrolyte, which eliminates most free iodide ions, thus preventing the consequent dissolution of the cathode‐plated iodine as triiodides.     

(Ph4P)2[Be3(μ‐OH)3(H2O)6]Cl5: Kristallstruktur und DFT‐Rechnungen

Bis(tetraphenylphosphonium)‐tris(μ‐hydroxo)hexaaquatriberylliumpentachloride, (Ph₄P)₂[Be₃(μ‐OH)₃(H₂O)₆]Cl₅ ( 1 ), was surprisingly obtained by reaction of (Ph₄P)N₃ · n H₂O with BeCl₂ in dichloromethane suspension and subsequent crystallization from acetonitrile to give single crystals of composition 1· 5.25CH₃CN. According to the crystal structure determination space group P , Z = 2, lattice dimensions at 100 K: a = 1354.8(2), b = 1708.7(2), c = 1753.2(2) pm, α = 114.28(1)°, β = 94.80(1)°, γ = 104.51(1)°, R₁ = 0.0586] the [Be₃(μ‐OH)₃(H₂O)₆]³⁺ cations form six‐mem‐bered Be₃O₃ rings with boat conformation and distorted tetrahedrally coordinated beryllium atoms with the terminally coordinated H₂O molecules. The structure ist characterized by a complicated three dimensional hydrogen‐bridging network including O–H ··· O, O–H ··· Cl, and O–H ··· NCCH₃ contacts. DFT calculations result in nearly planar [Be₃(OH)₃] six‐membered ring conformations.     

Oxidizing Elemental Platinum with Oleum under Harsh Conditions: The Unique Tris(disulfato)platinate(IV) [Pt(S2O7)3]2− Anion

For the first time, direct oxidation of elemental platinum by a mineral acid to its tetravalent state was observed in course of the reaction of platinum with oleum (65 % SO₃) in the presence of barium carbonate. The reaction has been carried out in torch‐sealed glass ampoules at 160 °C and gave yellow single crystals of Ba[Pt(S₂O₇)₃](H₂SO₄)_0.5(H₂S₂O₇)_0.5 (triclinic, P$\bar 1$ , Z=2, a=992.05(2), b=1069.07(3), c=1114.22(3) pm, α=69.49(7), β=72.96(2), γ=72.93(1)°, V=1033.95(5) ų). The structure of Ba[Pt(S₂O₇)₃](H₂SO₄)_0.5(H₂S₂O₇)_0.5 exhibits the unique tris‐(disulfato)‐platinate anion [Pt(S₂O₇)₃]^2? with three chelating disulfate groups coordinated to the platinum atom. Charge balance is achieved by the Ba²⁺ ions, which are coordinated by (S₂O₇)^2? groups from the platinate complex and by disordered sulfuric acids and disulfuric acid molecules. Thermal decomposition of the bulk material revealed elemental platinum and barium sulfate as decomposition residual.     

Mechanism of Nickel(II)‐Catalyzed Oxidative C(sp2)−H/C(sp3)−H Coupling of Benzamides and Toluene Derivatives

The Ni‐catalyzed C(sp²)?H/C(sp³)?H coupling of benzamides with toluene derivatives was recently successfully achieved with mild oxidant iC₃F₇I. Herein, we employ density functional theory (DFT) methods to resolve the mechanistic controversies. Two previously proposed mechanisms are excluded, and our proposed mechanism involving iodine‐atom transfer (IAT) between iC₃F₇I and the Ni^II intermediate was found to be more feasible. With this mechanism, the presence of a carbon radical is consistent with the experimental observation that (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) completely quenches the reaction. Meanwhile, the hydrogen‐atom abstraction of toluene is irreversible and the activation of the C(sp²)?H bond of benzamides is reversible. Both of these conclusions are in good agreement with Chatani's deuterium‐labeling experiments.     

Atom Exchange Versus Reconstruction: (GexAs4−x)x− (x=2, 3) as Building Blocks for the Supertetrahedral Zintl Cluster [Au6(Ge3As)(Ge2As2)3]3−

The Zintl anion (Ge₂As₂)^2? represents an isostructural and isoelectronic binary counterpart of yellow arsenic, yet without being studied with the same intensity so far. Upon introducing [(PPh₃)AuMe] into the 1,2‐diaminoethane (en) solution of (Ge₂As₂)^2?, the heterometallic cluster anion [Au₆(Ge₃As)(Ge₂As₂)₃]^3? is obtained as its salt [K(crypt‐222)]₃[Au₆(Ge₃As)(Ge₂As₂)₃]?en?2 tol ( 1 ). The anion represents a rare example of a superpolyhedral Zintl cluster, and it comprises the largest number of Au atoms relative to main group (semi)metal atoms in such clusters. The overall supertetrahedral structure is based on a (non‐bonding) octahedron of six Au atoms that is face‐capped by four (Ge_xAs_4?x)^x? (x=2, 3) units. The Au atoms bind to four main group atoms in a rectangular manner, and this way hold the four units together to form this unprecedented architecture. The presence of one (Ge₃As)^3? unit besides three (Ge₂As₂)^2? units as a consequence of an exchange reaction in solution was verified by detailed quantum chemical (DFT) calculations, which ruled out all other compositions besides [Au₆(Ge₃As)(Ge₂As₂)₃]^3?. Reactions of the heavier homologues (Tt₂Pn₂)^2? (Tt=Sn, Pb; Pn=Sb, Bi) did not yield clusters corresponding to that in 1 , but dimers of ternary nine‐vertex clusters, {[AuTt₅Pn₃]₂}^4? (in 2 – 4 ; Tt/Pn=Sn/Sb, Sn/Bi, Pb/Sb), since the underlying pseudo‐tetrahedral units comprising heavier atoms do not tend to undergo the said exchange reactions as readily as (Ge₂As₂)^2?, according to the DFT calculations.