Labile hyperbranched polymers used as nanopore-forming agents in polymeric dielectrica

Hyperbranched polyesters containing labile triazene units in the main chain have been synthesized and characterized. These structure decompose photochemically upon UV irradiation and thermally above 160°C. Homogeneous incorporation of these globular, functional polymers in thermostabile polymer matrices (polyimides and BCB polymers) was possible. Smooth films from blends of thermolabile matrix and up to 50% hyperbranched polymers could be prepared and have been studied as insulating material in microelectronic multilayer applications.     

Crystal and Molecular Structure of 6α-Methyl-3,20-Dioxo-5β-Pregnan-17α-yl Acetate

The title compound 6α-methyl-3.20-dioxo-5β-pregnan-17α-yl acetate crystallizes in the monoclinic space group P 2₁ with two molecules in the unit cell and the lattice parameters a = 10.889, b = 11.056, c = 9.8029 Å, β = 101.51° The crystal structure is isostructural with medroxyprogesterone acetate and refined by full matrix least squares calculations up to the discrepancy factor R = 0.051.     

Stiba-, Arsa- and Phosphastannenes: Syntheses and Reactivities

A facile synthesis for unprecedented stibastannene ( 10 ) featuring a Sn=Sb-double bond together with the homologous arsa- ( 9 ) and phosphastannenes ( 8 ) is presented. Chloride abstraction from respective stannyl pnictinidenes [E=P ( 5 ), As ( 6 ), Sb ( 7 )], which were made accessible by reduction of ECl₃ addition products at an intramolecular phosphine-stabilized stannylene, gave the pnictastannenes in moderate yields. The pnictastannenes coordinate Pd(PPh₃)₂ fragments ( 12 – 14 ) and the phosphastannene forms also a nickel coordination compound with the Ni(PPh₃)₂-fragment ( 11 ). 2,3-Dimethylbutadiene shows a [2+4]-cycloaddition ( 15 – 17 ) in reaction with the pnictastannenes ( 8 – 10 ). Products of a [2+2]-addition ( 18 , 19 ) were isolated as the phosphaalkyne reaction products for 8 and 9 . Addition of an O−H bond at the Sn=P-bond was found in reaction of water with phosphastannene 8 . Reaction with ammonia afforded the NH₃-adducts ( 21 – 23 ) at the tin atom for pnictastannenes 8 – 10 . Only in the case of the arsastannene an azide reaction product featuring a three membered Sn−As−N-ring was obtained.