Synthesen und Charakterisierungen der ersten Tris‐ und Tetrakis(trifluormethyl)palladate(II) und ‐platinate(II), [M(CF3)3(PPh3)]— und [M(CF3)4]2— (M = Pd,Pt)

Syntheses and Characterizations of the First Tris and Tetrakis(trifluoromethyl) Palladates(II) and Platinates(II), [M(CF₃)₃(PPh₃)]^— and [M(CF₃)₄]^2— (M = Pd, Pt) Tris(trifluoromethyl)(triphenylphosphino)palladate(II) and platinate(II), [M(CF₃)₃PPh₃]^—, and the tetrakis(trifluoromethyl)metallates, [M(CF₃)₄]^2— (M = Pd, Pt), are prepared from the reactions of [MCl₂(PPh₃)₂] and Me₃SiCF₃ / [Me₄N]F or [I(CF₃)₂]^— salts in good yields. [Me₄N][M(CF₃)₃(PPh₃)] crystallize isotypically in the orthorhombic space group Pnma (no. 62) with Z = 4. The NMR spectra of the new compounds are described.     

Inorganic-organic framework structures; M(II) ethylenediphosphonates (M = Co, Ni, Mn) and a Mn(II) ethylenediphosphonato-phenanthroline

The reaction of nickel, cobalt, and manganese with 1,2-ethylenediphosphonic acid or 1,2-ethylenediphosphonic acid and 1,10-phenanthroline under hydrothermal conditions resulted in the pillared layered structures Co2(H2O)2(O3PC2H4PO3) (I) and Ni2(H2O)2(O3PC2H4PO3) (II), which are isostructural to a zinc phase that has previously been characterized by X-ray powder methods. In addition, a 1D chain structure, Mn(HO3P(CH2)2PO3H)(H2O)2(C12H8N2) (III), and a pillared layered structure, Mn(HO3P(CH2)2PO3H) (IV), were obtained. The structures of these phases were solved by single-crystal X-ray diffraction methods. The crystallographic data are as follows: compound I P21/n (No. 14), a = 5.6500(11) A, b = 4.7800(10) A, c = 15.330(3) A, beta = 98.50(3) degrees, V = 409.47(14) A3, Z = 2; compound II P21/n (No. 14), a = 5.5807(11) A, b = 4.7205(9) A, c = 15.250(3) A, beta = 98.55(3) degrees, V = 397.28(13) A3, Z = 2; compound III C2/c (No. 15), a = 12.109(2) A, b = 15.328(3) A, c = 9.848(2) A, beta = 108.88(3) degrees, V = 1729.5(6) A3, Z = 4; compound IV P (No. 2), a = 5.498(5) A, b = 7.715(6) A, c = 8.093(7) A, alpha = 82.986(12) degrees, beta = 75.565(12) degrees, gamma = 80.582(12)degrees, V = 326.7(5) A3, Z = 2. Magnetic measurements show antiferromagnetic behavior below TN = 7 K for I and 13 K for II.     

Thermodynamics, kinetics, and mechanism of (silox)3M(olefin) to (silox)3M(alkylidene) rearrangements (silox = tBu3SiO; M = Nb, Ta)

Olefin complexes (silox)(3)M(ole) (silox = (t)Bu(3)SiO; M = Nb (1-ole), Ta (2-ole); ole = C(2)H(4), C(2)H(3)Me, C(2)H(3)Et, C(2)H(3)C(6)H(4)-p-X (X = OMe, H, CF(3)), C(2)H(3)(t)Bu, (c)C(5)H(8), (c)C(6)H(10), (c)C(7)H(10) (norbornene)) rearrange to alkylidene isomers (silox)(3)M(alk) (M = Nb (1=alk), Ta (2=alk); alk = CHMe, CHEt, CH(n)Pr, CHCH(2)C(6)H(4)-p-X (X = OMe, H, CF(3) (Ta only)), CHCH(2)(t)Bu, (c)C(5)H(8), (c)C(6)H(10), (c)C(7)H(10) (norbornylidene)). Kinetics and labeling experiments suggest that the rearrangement proceeds via a delta-abstraction on a silox CH bond by the beta-olefin carbon to give (silox)(2)RM(kappa(2)-O,C-OSi(t)Bu(2)CMe(2)CH(2)) (M = Nb (4-R), Ta (6-R); R = Me, Et, (n)Pr, (n)Bu, CH(2)CH(2)C(6)H(4)-p-X (X = OMe, H, CF(3) (Ta only)), CH(2)CH(2)(t)Bu, (c)C(5)H(9), (c)C(6)H(11), (c)C(7)H(11) (norbornyl)). A subsequent alpha-abstraction by the cylometalated "arm" of the intermediate on an alpha-CH bond of R generates the alkylidene 1=alk or 2=alk. Equilibrations of 1-ole with ole' to give 1-ole' and ole, and relevant calculations on 1-ole and 2-ole, permit interpretation of all relative ground and transition state energies for the complexes of either metal.     

Study of Ba3M(II)M(IV)WO9 (M(II) = Ca, Zn; M(IV) = Ti, Zr) perovskite oxides: competition between 3C and 6H perovskite structures

We describe an investigation of Ba3MIIMIVWO9 oxides for MII = Ca, Zn, and other divalent metals and MIV = Ti, Zr. In general, a 1:2-ordered 6H (hexagonal, P63/mmc) perovskite structure is stabilized at high temperatures (1300 degrees C) for all of the Ba3MIITiWO9 oxides investigated. An intermediate phase possessing a partially ordered 1:1 double perovskite (3C) structure with the cation distribution, Ba2(Zn2/3Ti1/3)(W2/3Ti1/3)O6, is obtained at 1200 degrees C for Ba3ZnTiWO9. Sr substitution for Ba in the latter stabilizes the cubic 3C structure instead of the 6H structure. A metastable Ba3CaZrWO9 that adopts the 3C (cubic, Fmm) structure has also been synthesized by a low-temperature metathesis route. Besides yielding several new perovskite oxides that may be useful as dielectric ceramics, the present investigation provides new insights into the complex interplay of crystal chemistry (tolerance factor) and chemical bonding (anion polarization and d0-induced distortion of metal-oxygen octahedra) in the stabilization of 6H versus 3C perovskite structures for the Ba3MIIMIVWO9 series.     

Quaternäre Caesium‐Kupfer(I)‐Lanthanoid(III)‐Selenide vom Typ CsCu3M2Se5 (M = Sm,Gd — Lu)

Quaternary Cesium Copper(I) Lanthanoid(III) Selenides of the Type CsCu₃M₂Se₅ (M = Sm, Gd — Lu) By oxidation of mixtures of copper and lanthanoid metal with elemental selenium in molar ratios of 1 : 1 : 2 and in addition of CsCl quaternary cesium copper(I) lanthanoid(III) selenides with the formula CsCu₃M₂Se₅ (M = Sm, Gd — Lu) were obtained at 750 °C within a week from torch‐sealed evacuated silica tubes. An excess of CsCl as flux helps to crystallize golden yellow or red, needle‐shaped, water‐resistant single crystals. The crystal structure of CsCu₃M₂Se₅ (M = Sm, Gd — Lu) (orthorhombic, Cmcm, Z = 4; e. g. CsCu₃Sm₂Se₅: a = 417.84(3), b = 1470.91(8), c = 1764.78(9) pm and CsCu₃Lu₂Se₅: a = 407.63(3), b = 1464.86(8), c = 1707.21(9) pm, respectively) contains [MSe₆]^9— octahedra which share edges to form double chains running along [100]. Those are further connected by vertices to generate a two‐dimensional layer parallel to (010). By edge‐ and vertex‐linking of [CuSe₄]^7— tetrahedra two crystallographically different Cu⁺ cations build up two‐dimensional puckered layers parallel to (010) as well. These sheet‐like structure interconnects the equation/tex2gif-stack-3.gif{[M₂Se₅]^4—} layers to create a three‐dimensional network according to equation/tex2gif-stack-4.gif{[Cu₃M₂Se₅]^—}. Thus empty channels along [100] form, apt to take up the Cs⁺ cations. These are surrounded by eight plus one Se^2— anions in the shape of (2+1)‐fold capped trigonal prisms with Cs—Se distances between 348 and 368 pm (8×) and 437 (for M = Sm) or 440 pm (for M = Lu), respectively, for the ninth ligand.     

Transition‐Metal Chemistry of Alkaline‐Earth Elements: The Trisbenzene Complexes M(Bz)3 (M=Sr,Ba)

We report the synthesis and spectroscopic identification of the trisbenzene complexes of strontium and barium M(Bz)₃ (M=Sr, Ba) in low‐temperature Ne matrix. Both complexes are characterized by a D₃ symmetric structure involving three equivalent η⁶‐bound benzene ligands and a closed‐shell singlet electronic ground state. The analysis of the electronic structure shows that the complexes exhibit metal–ligand bonds that are typical for transition metal compounds. The chemical bonds can be explained in terms of weak donation from the π MOs of benzene ligands into the vacant (n?1)d AOs of M and strong backdonation from the occupied (n?1)d AO of M into vacant π* MOs of benzene ligands. The metals in these 20‐electron complexes have 18 effective valence electrons, and, thus, fulfill the 18‐electron rule if only the metal–ligand bonding electrons are counted. The results suggest that the heavier alkaline earth atoms exhibit the full bonding scenario of transition metals.     

Transition‐Metal Chemistry of Alkaline‐Earth Elements: The Trisbenzene Complexes M(Bz)3 (M=Sr,Ba)

We report the synthesis and spectroscopic identification of the trisbenzene complexes of strontium and barium M(Bz)₃ (M=Sr, Ba) in low‐temperature Ne matrix. Both complexes are characterized by a D₃ symmetric structure involving three equivalent η⁶‐bound benzene ligands and a closed‐shell singlet electronic ground state. The analysis of the electronic structure shows that the complexes exhibit metal–ligand bonds that are typical for transition metal compounds. The chemical bonds can be explained in terms of weak donation from the π MOs of benzene ligands into the vacant (n?1)d AOs of M and strong backdonation from the occupied (n?1)d AO of M into vacant π* MOs of benzene ligands. The metals in these 20‐electron complexes have 18 effective valence electrons, and, thus, fulfill the 18‐electron rule if only the metal–ligand bonding electrons are counted. The results suggest that the heavier alkaline earth atoms exhibit the full bonding scenario of transition metals.     

Cyanidverbrückte Dreikernkomplexe mit zentralen M(Cyclam)‐Einheiten

Cyanide Bridged Trinuclear Complexes with Central M(Cyclam) Units Reactions between metal cyclam complexes M(Cyclam)X_n and organometallic cyanides L_nM′‐CN yielded trinuclear complexes L_nM′‐CN‐M(Cyclam)‐NC‐M′L_n with M = Mn, Fe, Co, Ni and M′ = Cr, Fe, Ru. They were probed with structural, spectroscopic and electrochemical methods for electronic interactions between the involved metal centers.     

Ligand dependence of metal-metal bonding in the d(3)d(3) dimers M(2)X(9)(n-) (M(III) = Cr, Mo, W; M(IV) = Mn, Tc, Re; X = F, Cl, Br, I)

The ligand dependence of metal-metal bonding in the d(3)d(3) face-shared M(2)X(9)(n-) (M(III) = Cr, Mo, W; M(IV) = Mn, Tc, Re; X = F, Cl, Br, I) dimers has been investigated using density functional theory. In general, significant differences in metal-metal bonding are observed between the fluoride and chloride complexes involving the same metal ion, whereas less dramatic changes occur between the bromide and iodide complexes and minimal differences between the chloride and bromide complexes. For M = Mo, Tc, and Re, change in the halide from F to I results in weaker metal-metal bonding corresponding to a shift from either the triple metal-metal bonded to single bonded case or from the latter to a nonbonded structure. A fragment analysis performed on M(2)X(9)(3-) (M = Mo, W) allowed determination of the metal-metal and metal-bridge contributions to the total bonding energy in the dimer. As the halide changes from F to I, there is a systematic reduction in the total interaction energy of the fragments which can be traced to a progressive destabilization of the metal-bridge interaction because of weaker M-X(bridge) bonding as fluoride is replaced by its heavier congeners. In contrast, the metal-metal interaction remains essentially constant with change in the halide.     

钛,锆和铪羰基化合物M(CO)_n(M=Ti,Zr,Hf;n=4～7)的理论研究

利用密度泛函方法对标题化合物的平衡几何、热化学及振动频率进行了理论预测,发现这3种金属原子都有相似的M(CO)n(n=4～7)结构.全局最低构型对M(CO)7都是单态C3v戴帽八面体7S-1,对M(CO)6都是三重态D3d畸变八面体6T(而对应的单重态M(CO)5仅比它低不到21 kJ·mol-1).对M(CO)n(n=5,4)都是三重态6S-1,其构型分别为从6T中移去1个或2个CO基的衍生物5T和4T.此外,五重态的D3h的三角双锥M(CO)5和单态的Td四面体M(CO)4以及能量更高的含有C和O同时与金属成键的独特配位CO基的M(CO)6和M(CO)3也被发现.最后,给出M(CO)7→M(CO)6+CO反应的离解能.并讨论了金属18价电子的Ti(CO)7存在的可能性.     

Die Oxidnitridselenide M3ONSe2 dreiwertiger Lanthanoide (M = Ce – Nd)

The Oxide Nitride Selenides M₃ONSe₂ of Trivalent Lanthanoids (M = Ce – Nd) Oxide nitride selenides of the trivalent lanthanoids (M = Ce – Nd) with the composition M₃ONSe₂ can be prepared by the oxidation of the respective lanthanoid metal with selenium and sodium azide (NaN₃) in presence of impurities containing oxygen when the corresponding lanthanoid trichloride (MCl₃) is used as sodium trap for the coformation of NaCl. The thermal treatment of these mixtures along with additional NaCl as flux at 900 °C in evacuated silica tubes secures the formation of fawn, transparent, lath‐shaped crystals. The monoclinic structure (C2/m, Z = 6) was determined from X‐ray single‐crystal diffraction data (Ce₃ONSe₂: a = 2480.51(14), b = 406.85(3), c = 952.83(6) pm, β = 95.506(4)°; Pr₃ONSe₂: a = 2462.72(14), b = 403.74(3), c = 947.26(6) pm, β = 95.731(4)°; Nd₃ONSe₂: a = 2440.35(14), b = 401.48(3), c = 944.02(6) pm, β = 95.763(4)°). Five crystallographically different M³⁺ cations reside in six‐ to eightfold coordination of the respective anions (three independent O^2?/N^3? and Se^2? each), for which a statistic distribution of the light elements (O^2? : N^3? = 1 : 1) has to be assumed. However, the main features of the crystal structure are (O^2?/N^3?)‐centred (M³⁺)₄ tetrahedra. For the first time ever within the same structure of this kind, condensation of these anion‐centred cation polyhedra forming strands and layers simultaneously could be detected. Cis‐edge connected [(O/N)M₄]^9.5+ tetrahedra build up the chain components running along [010], which are already known as dominating core in some crystal structures of pure nitride chalcogenides (e.g. Sm₄N₂S₃ and Tb₄N₂Se₃). A new motif of condensed tetrahedral units comprises the second feature. By fusing [(O/N)M₄]^9.5+ tetrahedra via vertices and edges, one‐dimensional strand sections from the cationic sheets of the Ce₂O₂S‐type structure, which are further connected only via common vertices to form a lower‐condensed steplike two‐dimensional layer , spreading parallel to the (100) plane, emerge for the very first time.     

Structural and Spectroscopic Studies of [M((x)tu)4]+ Systems (M = Cu,Ag; (x)tu = (substituted) Thiourea)

In a low‐temperature redetermination of improved precision of the structure of [Cu(tu)₄]₂(SiF₆) (‘tu’ = thiourea, SC(NH₂)₂), Cu–S range between 2.3173–2.3433(8), < > 2.336(11) Å, with S–Cu–S 92.72(3)–118.75(12)°. The first structure determination of a 1:4 adduct of a silver(I) salt with a (substituted) thiourea ligand is also reported, for silver(I) nitrate with ‘ethylenethiourea’, (‘etu’ = SC(NHCH₂)₂), as a monohydrate [Ag(etu)₄](NO₃)·H₂O, wherein Ag–S range between 2.544–2.637(2), < > 2.59(4) Å, S–Ag–S 87.88–117.57(7)°. Bands in the far‐IR spectra of these compounds are assigned to ν(MS) modes, and the frequencies are compared with those predicted by previously established correlations between ν(MS) and the M–S bond length d(MS) for copper or silver complexes with tu or etu ligands.