μ3‐η2:η2:η2‐Coordination of Primary Silane on a Triruthenium Plane

A μ₃‐η²:η²:η²‐silane complex, [(Cp*Ru)₃(μ₃‐η²:η²:η²‐H₃SitBu)(μ‐H)₃] ( 2 a ; Cp*=η⁵‐C₅Me₅), was synthesized from the reaction of [{Cp*Ru(μ‐H)}₃(μ₃‐H)₂] ( 1 ) with tBuSiH₃. Complex 2 a is the first example of a silane ligand adopting a μ₃‐η²:η²:η² coordination mode. This unprecedented coordination mode was established by NMR and IR spectroscopy as well as X‐ray diffraction analysis and supported by a density functional study. Variable‐temperature NMR analysis implied that 2 a equilibrates with a tautomeric μ₃‐silyl complex ( 3 a ). Although 3 a was not isolated, the corresponding μ₃‐silyl complex, [(Cp*Ru)₃(μ₃‐η²:η²‐H₂SiPh)(H)(μ‐H)₃] ( 3 b ), was obtained from the reaction of 1 with PhSiH₃. Treatment of 2 a with PhSiH₃ resulted in a silane exchange reaction, leading to the formation of 3 b accompanied by the elimination of tBuSiH₃. This result indicates that the μ₃‐silane complex can be regarded as an “arrested” intermediate for the oxidative addition/reductive elimination of a primary silane to a trinuclear site.     

Unprecedented μ-η2:η2-Pyrazolate Coordination in [{Yb(η2-tBu2pz)(μ-η2:η2-tBu2pz)(thf)}2]

A higher degree of coordination saturation is attainable through the unusual coordination mode in the title compound 1 , in which the central pyrazolate groups function both as chelating and as bridging ligands. There is some asymmetry in the bridging, and the N atoms of each μ-η²:η²-pyrazolato ligand are 0.07–0.11 Å closer to one of the two Yb centers.     

Synthesis and Reactivity of Nickel‐Stabilised μ2:η2,η2‐P2, As2 and PAs Units

The reactivity of two paramagnetic nickel(I) compounds, CpNi(NHC) (where Cp=cyclopentadienyl; NHC=1,3‐bis(2,4,6‐trimethylphenyl)imidazol‐2‐ylidene (IMes) or 1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene (IPr)), towards [Na(dioxane)_x][PnCO] (Pn=P, As) is described. These reactions afford symmetric bimetallic compounds (μ²:η²,η²‐Pn₂){Ni(NHC)(CO)}₂. Several novel intermediates en route to such species are identified and characterised, including a compound containing the PCO^? anion in an unprecedented μ²:η²,η²‐binding mode. Ultimately, on treatment of the (μ²:η²,η²‐Pn₂){Ni(IMes)(CO)}₂ compounds with carbon monoxide, the Pn₂ units can be released, affording P₄ in the case of the phosphorus‐containing species, and elemental arsenic in the case of (μ²:η²,η²‐As₂){Ni(IMes)(CO)}₂.     

Bis‐μ‐oxo and μ‐η2:η2‐peroxo dicopper complexes studied within (time‐dependent) density‐functional and many‐body perturbation theory

Based on the equilibrium geometries of [Cu₂(dbdmed)₂O₂]²⁺ and [Cu₂(en)₂O₂]²⁺ obtained within density‐functional theory, we investigate their molecular electronic structure and optical response. Thereby results from occupation‐constrained as well as time‐dependent DFT (ΔSCF and TDDFT) are compared with Green's function‐based approaches within many‐body perturbation theory such as the GW approximation (GWA) to the quasiparticle energies and the Bethe‐Salpeter equation (BSE) approach to the optical absorption. Concerning the ground‐state energies and geometries, no clear trend with respect to the amount of exact exchange in the DFT calculations is found, and a strong dependence on the basis sets is to be noted. They affect the energy difference between bis‐μ‐oxo and μ‐η²:η²‐peroxo complexes by as much as 0.8 eV (18 kcal/mol). Even stronger, up to 5 eV is the influence of the exchange‐correlation functional on the gap values obtained from the Kohn‐Sham eigenvalues. Not only the value itself but also the trends observed upon the bis‐μ‐oxo to μ‐η²:η²‐peroxo transition are affected. In contrast, excitation energies obtained from ΔSCF and TDDFT are comparatively robust with respect to the details of the calculations. Noteworthy, in particular, is the near quantitative agreement between TDDFT and GWA+BSE for the optical spectra of [Cu₂(en)₂O₂]²⁺. © 2013 Wiley Periodicals, Inc.     

Aktivierung von Schwefelkohlenstoff an Trirutheniumclustern: Synthese und Kristallstruktur von [Ru3(CO)5(μ‐H)2(μ‐PCy2)(μ‐Ph2PCH2PPh2){μ‐η2‐PCy2C(S)}(μ3‐S)] und [Ru3(CO)5(CS)(μ‐H)(μ‐PtBu2)(μ‐PCy2)2(μ3‐S)]

Activation of Carbon Disulfide on Triruthenium Clusters: Synthesis and X‐Ray Crystal Structure Analysis of [Ru₃(CO)₅(μ‐H)₂(μ‐PCy₂)(μ‐Ph₂PCH₂PPh₂){μ‐η²‐PCy₂C(S)}(μ₃‐S)] and [Ru₃(CO)₅(CS)(μ‐H)(μ‐P^tBu₂)(μ‐PCy₂)₂(μ₃‐S)] [Ru₃(CO)₆(μ‐H)₂(μ‐PCy₂)₂(μ‐dppm)] ( 1 ) (dppm = Ph₂PCH₂PPh₂) reacts under mild conditions with CS₂ and yields by oxidative decarbonylation and insertion of CS into one phosphido bridge the opened 50 VE‐cluster [Ru₃(CO)₅(μ‐H)₂(μ‐PCy₂)(μ‐dppm){μ‐η²‐PCy₂C(S)}(μ₃‐S)] ( 2 ) with only two M–M bonds. The compound 2 crystallizes in the triclinic space group P 1 with a = 19.093(3), b = 12.2883(12), c = 20.098(3) Å; α = 84.65(3), β = 77.21(3), γ = 81.87(3)° and V = 2790.7(11) ų. The reaction of [Ru₃(CO)₇(μ‐H)(μ‐P^tBu₂)(μ‐PCy₂)₂] ( 3 ) with CS₂ in refluxing toluene affords the 50 VE‐cluster [Ru₃(CO)₅(CS)(μ‐H)(μ‐P^tBu₂)(μ‐PCy₂)₂(μ₃‐S)] ( 4 ). The compound cristallizes in the monoclinic space group P 2₁/a with a = 19.093(3), b = 12.2883(12), c = 20.098(3) Å; β = 104.223(16)° and V = 4570.9(10) ų. Although in the solid state structure one elongated Ru–Ru bond has been found the complex 4 can be considered by means of the ³¹P‐NMR data as an electron‐rich metal cluster.     

5-雄烯-3β, 7α, 17β-三醇和5-雄烯-3β, 7β, 17β-三醇的合成

以5-雄烯二醇为原料,用微生物转化的方法合成了两个重要的神经甾体5-雄烯-3β, 7α, 17β-三醇和5-雄烯-3β, 7β, 17β-三醇。所用菌种总枝毛霉为我们自己筛选,并首次应用于5-雄烯-3β, 7α, 17β-三醇和5-雄烯-3β, 7β, 17β-三醇的合成中。