Synthese und thermische Eigenschaften von molekularen Clusterverbindungen zusammengesetzt aus Elementen der Gruppen 11‐13‐16

Syntheses and Thermal Properties of Cluster Molecules, formed from Groups 11‐13‐16 Elements In the presence of PPh₃, CuX (X = Cl, CH₃COO) or AgOC(O)C₆H₅ and GaCl₃ react in THF with S(SiMe₃)₂ or Se(SiMe₃)₂ to yield [Cu₆Ga₈Cl₄S₁₃(PPh₃)₆] ( 1 ), [Cu₆Ga₈Cl₄Se₁₃(PPh₃)₆] ( 2 ), [Ag₆Ga₈Cl₄S₁₃(PPh₃)₆] ( 4 ) and [Ag₆Ga₈Cl₄Se₁₃(PPh₃)₆] ( 5 ). The use of PⁿPr₂Ph instead of PPh₃ and subsequent layering with n‐hexane leads to the formation of the cluster [Cu₆Ga₈Cl₄Se₁₃(PⁿPr₂Ph)₁₂] ( 3a , 3b ). Reaction of CuCl, GaCl₃ and PⁿPr₃ with Se(SiMe₃)₂ in THF results in the crystallisation of the ionic cluster (HPⁿPr₃)₂[Cu₂Ga₄Cl₄Se₆(PⁿPr₃)₄] ( 6 ). The structures of 1 — 6 were determined by X‐ray single crystal structure analysis. Thermogravimetric measurements of the cluster molecules and powder diffraction patterns of the remaining powders reveal the potential use of them as single source precursor compounds for the synthesis of the related ternary solid state materials.     

Application of Methyl Bisphosphine‐Ligated Palladium Complexes for Low Pressure N‐11C‐Acetylation of Peptides

A mild and effective method is described for ¹¹C‐labeling of peptides selectively at the N‐terminal nitrogen or at internal lysine positions. The presented method relies on the use of specific biphosphine palladium–methyl complexes and their high reactivity towards amino‐carbonylation of amine groups in the presence [¹¹C]carbon monoxide. The protocol facilitates the production of native N‐¹¹C‐acetylated peptides, without any structural modifications and has been applied to a selection of bioactive peptides.     

Synthese und Charakterisierung von InIII–SnII‐Halogenido‐Alkoxiden und von Indiumtri‐tert‐butoxid

Synthesis and Characterization of In^III–Sn^II‐Halogenido‐Alkoxides and of Indiumtri‐ tert ‐butoxide Through sodium halide elimination between Indium(III) halides and sodium‐tri‐tert‐butoxistannate(II) or sodium‐tri‐tert‐butoxigermanate(II) the three new heterometallic and heteroleptic alkoxo compounds THF · Cl₂In(OtBu)₃Sn ( 1 ), THF · Br₂In(OtBu)₃Sn ( 2 ), and THF · Cl₂In‐ (OtBu)₃Ge ( 3 ), have been synthesized. The molecular structures of 1 and 2 in the solid state follow from single crystal X‐ray structure determinations while structural changes in solution may be derived from temperature dependant NMR spectroscopy. The crystal structures of compounds 1 and 2 are despite different halide atoms isostructural. Both crystallize in the ortho‐rhombic crystal system in space group Pbca with eight molecules per unit cell. The heavy atoms occupy the apical positions of empty trigonal bipyramids of almost point symmetry C_s(m) and are connected through oxygen atoms occupying the equatorial positions. The indium atoms in both compounds are in the centers of distorted octahedra from 4 oxygen and 2 halogen atoms whereas the tin atoms are coordinated by three oxygen atoms in a trigonal pyramidal fashion. Although the coordinative bonding of THF to indium leads to an asymmetry of the molecule the NMR spectra in solution are simple showing a more complex pattern at lower temperatures. Tri(tert‐butoxi)indium [In(OtBu)₃]₂ ( 4 ), is obtained through alcoholysis of In(N(Si(CH₃)₃)₂)₃ using tert‐butanol in toluene and is crystallized from hexane. The X‐ray structure determination of 4 seems to be the first one of a homoleptic and homometallic indiumalkoxide. Compound 4 crystallizes in the monoclinic crystal system in a dimeric form with eight molecules in the unit cell of space group C2/c. The dimeric units have C₂ symmetry and an almost planar In₂O₂ ring which originates from oxygen bridging of the monomers. Through this mutual Lewis acid base interaction the indium atoms get four oxygen ligands in a distorted tetrahedral environment.     

Metal‐Free meta‐Selective Alkyne Oxyarylation with Pyridine N‐Oxides: Rapid Assembly of Metyrapone Analogues

An efficient metal‐free oxyarylation of electron‐poor alkynes with pyridine N‐oxides has been developed. This transformation affords meta‐substituted pyridines analogous to the drug metyrapone in high regioselectivities. Density functional theory (DFT) calculations provided important insight into the mechanism. Evaluation of the inhibitory properties revealed the most active CYP11B1 inhibitor of these derivatives, with two‐digit nanomolar inhibitory activity akin to that of metyrapone.