Falk Lissner

First experimental evidence of alluaudite-like phosphates with high Li-content: the (Na1-xLix)MnFe2(PO4)3 series (x = 0 to 1)

Members of the Na 1-x Li x MnFe 2 (PO 4 ) 3 series, with the alluaudite structure type, were synthesized by solid-state reaction in air. The crystal structure refinement of the NaMnFe 2 (PO 4 ) 3 end-member (space group C2/ c, Z = 4, a = 12.018(2), b = 12.565(3), c = 6.415(1) A, β = 114.33(3)°), a synthetic compound with a chemical composition corresponding to the idealized composition of the Buranga alluaudite, was carried out to R 1 = 0.026. The following cationic distribution was observed: Na + + □ in A(1) and A(2)′ (□ denotes lattice vacancies), Mn 2+ in M(1), Fe 3+ + Fe 2+ in M(2). The A(2)′ site exhibits a distorted gable disphenoid morphology and is found at the (0, y, ¼) (y ≈ 0) position in channel 2 of the alluaudite structure. The crystal structure of Na 0.5 Li 0.5 MnFe 2 (PO 4 ) 3 (space group C2/ c, Z = 4, a = 11.988(2), b = 12.500(3), c = 6.392(1) A, β = 114.67(3)°), refined to R 1 = 0.034, leads to the cationic distribution: Li + + Na + + □ in A(2)′, Na + + □in A(1), Mn 2+ in M(1), Fe 3+ + Fe 2+ in M(2). Thus, the substitution mechanism involved in the replacement of Na by Li in the Na 1-x Li x MnFe 2 (PO 4 ) 3 alluaudite-like compounds corresponds to □ + Na □ Li + □, with x ranging from 0.00 to 0.90.

M10S14O-type oxysulphides (M≡La, Ce, Pr, Nd, Sm) as an oxygen trap in oxidation reactions of reduced lanthanide chlorides with sulphur

Abstract Oxidation of reduced chlorides (KM2Cl5; M  Nd, Sm) or chloride-hydrides (MClH0.67; M  La, Ce, Pr) of the lanthanides with sulphur in the presence of NaCl in the latter case (tantalum capsule, 850 °C, 7 days) results in the formation of binary sulphides and ternary chlorides with potassium and sodium respectively, both with trivalent cations (M3+), as the main products. Oxidic impurities (e.g. MOCl) react to yield M10S14O-type oxysulphides (M  La, Ce, Pr, Nd, Sm) in small amounts as bead-shaped single crystals of high quality (M10S14O, tetragonal, I4 1 acd (no. 142), Z = 8; M  La: a = 1536.51(4) pm, c = 2037.85(9) pm, R = Rw = 0.028; M  Ce: a = 1521.24(4) pm, c = 2018.43(9) pm, R = 0.014, Rw = 0.013; M  Pr: a = 1511.63(4) pm, c = 2006.27(9) pm, R = 0.028, Rw = 0.029; M  Nd: a = 1503.80(4) pm, c = 1996.46(8) pm, R = 0.015, Rw = 0.014; M  Sm: a = 1485.96(4) pm, c = 1974.04(8) pm, R = 0.016, Rw = 0.014). Their crystal structure is built up from isolated O2−-centred tetrahedra [OM4]10+ which are surrounded by a “sea” of lanthanide sulphide according to the formulation [OM4]S7M6S7. Three crystallographically independent M3+ cations occur with coordination numbers of eight (M1: seven plus one S2−; M2: six plus one S2− and one O2−, both bicapped trigonal prisms; M3: eight S2−, trigonal dodecahedron). Four different S2− (coordination numbers from four plus one to six) provide for the necessary coupling of the isolated [O(M2)4] tetrahedra to their metal sulphide vicinity.

First crystal structure determination and high-frequency EPR study of an organoarsanecopper radical complex

Abstract The red radical complex {(μ-bptz)[Cu(AsPh3)2]2}(BF4) 1, bptz=3,6-bis(2-pyridyl)-1,2,4,5-tetrazine, was obtained as a stable species and characterized by X-ray crystallography, spectroelectrochemistry and EPR at 9.5 and 285 GHz. Comparison with the previously reported {(μ-bptz)[Cu(PPh3)2]2}(BF4) 2 reveals longer Cu-element bonds by about 0.1 A but otherwise a similar “organic sandwich” structure involving intramolecular π(phenyl)–π(tetrazine)–π(phenyl) interactions, a 3+1 coordination at the copper(I) centers, and averaged tetrazine intraring bond distances. Reversible oxidation to a blue dication with an intense MLCT band at 650 nm occurs at −0.24 V vs. Fc+/o. EPR studies show the effect of the higher spin–orbit coupling constant of the As vs. P atoms through slightly larger g anisotropy as determined through high frequency measurements.

Identifying Intermediates of Sequential Electron and Hydrogen Loss from a Dicarbonylcobalt Hydride Complex

Coordination compounds of cobalt have recently received special attention in the context of hydrogen production (“splitting water with cobalt”) and conversion. Within these studies the mechanistic sequence of electron and proton or hydrogen transfer has frequently been discussed. Although cobalt carbonyl hydrides, especially [Co(CO)4H] have been the subject of many studies since their development by Hieber and co-workers in the 1930s and since their use in hydroformylation processes, the hydrogen-producing reactions were mainly reported with non-organometallic cobalt complexes, involving ligands such as oligodentate imines, glyoximes, phosphanes, and macrocycles. Herein we describe the synthesis and characterization of the first dicarbonylhydridocobalt complex [Co(CO)2(dippf)H] = [(1)H] with a 1,1’-diphosphinoferrocene ligand (dippf = 1,1’-bis(diisopropylphosphino)ferrocene) and its chemical and (spectro)electrochemical oxidation via [(1)H] to the structurally characterized product [Co(CO)2(dippf)] + = [(1)], which has formally lost a hydrogen atom and can be reduced to a Co species [(1)] (Scheme 1). In contrast to the above-mentioned complexes, in our series the presence of CO ligands makes it possible to monitor several intermediates by IR spectroelectrochemistry. The family of 1,1’-bis(diorganophosphino)ferrocene ligands has been widely used in catalysis and for functional molecular materials; these ligands can also be considered as redox noninnocent due to the reversible oxidation of the ferrocene framework. For instance, it was shown that the assignment of the oxidation site in ambivalent [FeRu] heterobimetallic complexes involving 1,1’-bis(diorganophosphino)ferrocene ligands is not trivial. Reaction of [Co(CO)4H] with dippf leads to compound [(1)H]. In addition to the H and P NMR spectroscopy the crystal structure analysis (Figure 1A, Table 1) confirms the configuration with one metal–hydride bond (at a disordered position) pointing toward the inside—probably a result of the steric crowding from the PiPr2 groups at the outside. Both hydride positions (at half occupancy) were thus found crystallographically as capping the approximately tetrahedral CuP2C2 coordination core. DFT calculations confirm the experimental structure as a stable arrangement (Table 1, see also Figure S1 in the Supporting Information). Cyclic voltammetry at ambient temperature (Figure 2A) and at 50 8C in CH2Cl2 (Figure S2) showed an oxidation of

Single crystals of F-Tm2S3 and T-Yb2S3☆

Abstract The reaction of thulium and ytterbium with sulphur (2:3 molar ratios, 850°C, 7 days) in sealed silica containers yields single-crystal sesquisulphides in the presence of some NaCl as a flux. Yellow needles of F-Tm2S3 (monoclinic, P21/m (no. 11), Z = 4, α = 1115.13(9) pm, b . 389.42(3) pm, c = 1089.06(9) pm, β = 108.811(7)°, R = 0.049, Rw = 0.037) and orange beads of T-Yb2S3 (cubic, Ia 3 (no. 206), Z = 16, a = 1246.83(3) pm, R = 0.015, Rw = 0.014) are the single-phase binary products. There are four crystallographically independent Tm3+ in F-Tm2S3, two in distorted octahedral, one in monocapped and one in bicapped trigonal prismatic coordination of S2−. Previously addressed as Tm2S3-II, it is the only sesquisulphide structure known so far that offers coordination numbers of six, seven and eight for M3+ simultaneously. The crystal structure of T-Yb2S3 (bixbyite-type structure, well known for the sesquioxides of the “heavier” lanthanides as C type) exhibits two crystallographically independent Yb3+ in a more or less distorted octahedral neighbourhood of S2−.

Template-controlled assembly of ditopic catechol phosphines: a strategy for the generation of complexes of bidentate phosphines with different bite angles.

A rational approach to the synthesis of heterobi- or -trimetallic complexes based upon self-assembly of a flexible ditopic catechol-phosphine ligand with [(cod)PdCl(2)] and simple metal halides such as GaCl(3), BiCl(3), SnCl(4), or ZrCl(4) is described. All products were characterized by spectroscopic and analytical data and single-crystal X-ray diffraction studies. The molecular structures can be described in terms of cis-configured palladium complexes with supramolecular bisphosphine ligands that are formed by the assembly of two phosphine catecholate fragments on a main group/transition metal template. Of particular interest are the distinct decreases in P-Pd-P bite angles and P...P distances between the ligating atoms with increasing covalent radii of the templates. The range of these variations is of a magnitude similar to that of the geometrical changes in known families of complexes containing molecular bidentate ligands. Solution NMR studies give further evidence that in several cases the mu(2)-bridging coordination of two of the catechol oxygen atoms in the template complexes is broken under the influence of donor solvents, thus allowing the supramolecular ligand to be switched between tetradentate -O(2)P(2) and bidentate -P(2) coordination modes.

Metal Dependence of Network Dimensionality in 1,2,4‐Diazaphospholide Coordination Polymers

The successful utilization of both P- and N-based homotopic ligands suggested that heterotopic P,N-heterocycles are likewise viable building blocks, in which the presence of two types of donor sites with different ligating power might allow, as an additional advantage, the observation of switchable coordination behavior. In particular, we envisaged that the known preference of the two-coordinate phosphorus to behave as soft donor should allow the ligand to use both Pand N-donor functions to bind to soft metal ions, whereas only N-donor sites should be involved in binding of hard metal ions, thus enabling the construction of coordination polymers with different network topologies from the same ligand. Here, we report on the results of some initial experiments conducted along these lines. The bridging ligand employed, 1,2,4-diazaphospholide (dap), [6] was chosen because

Electronic properties of Fabre charge-transfer salts under various temperature and pressure conditions

Using density functional theory, we determine parameters of tight-binding Hamiltonians for a variety of Fabre charge transfer salts, focusing, in particular, on the effects of temperature and pressure. Besides relying on previously published crystal structures, we experimentally determine two new sets of structures: (TMTTF)2SbF6 at different temperatures and (TMTTF)2PF6 under various hydrostatic pressures. We find that a few trends in the electronic behavior can be connected to the complex phase diagram shown by these materials. Decreasing temperature and increasing pressure cause the systems to become more two dimensional. We analyze the importance of correlations by considering an extended Hubbard model parameterized using Wannier orbital overlaps and show that while charge order is strongly activated by the intersite Coulomb interaction, the magnetic order is only weakly enhanced. Both orders are suppressed when the effective pressure is increased.

Establishing the Chelating α‐Azocarbonyl Function in π‐Acceptor Ligands

Four-center two-step redox systems [see Eq. (1)] with coordinating heteroatoms in 1,4-positions have long played a prominent role in coordination chemistry as potentially noninnocent chelate ligands. Reducible a-diimines (E, E’= NR) including 1,4-diazabutadienes, o-quinonediimines or “polypyridines” of the 2,2’-bipyridine or 1,10phenanthroline type have thus been studied particularly under the aspect of light-induced charge transfer, while the more easily reduced a-diketones and especially o-quinones (E, E’= O) can exhibit the phenomenon of redox isomerism (“valence tautomerism”) in their transition-metal complexes. The related complexes of a-dithiolene ligands (E, E’= S), long known and recently reinvestigated, are often cited as prototypes of coordination compounds with partially covalent metal–donor bonds.

The crystal structures of zincroselite and gaitite Two natural polymorphs of Ca2Zn[AsO4]2·2H2O from Tsumeb, Namibia

The crystal structures of zincroselite and gaitite, two polymorphs of Ca 2 Zn[AsO 4 ] 2 ·2H 2 O from Tsumeb (Namibia), were determined from single-crystal X-ray intensity data. The type crystal of zincroselite, monoclinic, P 2 1 / c , a = 5.827(1), b = 12.899(3), c = 5.646(1) A and β = 107.69(3)°, Z = 2, was refined with 935 unique reflections to R 1 = 2.61%. The mean bond distances are = 1.690 A, 2 O)> = 2.123 A and 2 O)> = 2.526 A. Gaitite, P 1, a = 5.899(1), b = 6.978(1) and c = 5.755(1) A, α = 97.41(3)°, β = 109.08(3)° and γ= 108.09(3)°, Z = 1, was refined with 914 unique reflections to R 1 = 1.77%. The mean bond distances are = 1.687 A, 2 O)> = 2.102 A and 2 O)> = 2.525 A. For both structures, the positions of all H atoms were isotropically refined and the hydrogen-bonding arrangement identified. The common structural unit of zincroselite and gaitite are [Ca 2 Zn(H 2 O) 2 O 8 (AsO 4 ) 2 ] 16- rods parallel to the c axis. The polymorphism of Ca 2 Zn[AsO 4 ] 2 ·2H 2 O referred to the glide plane c can easily be visualized with different rod-packings. Zincroselite and gaitite belong to the roselite and collinsite structure type, respectively.