Hans‐Jürgen Tiller

Malonate intercalation into layered chromium—zinc double hydroxides

Layered double hydroxides of type [Zn2Cr(OH)6]X · nH2O where X− = 12 mal2−, cis-[Cr(mal)2(H2O)2]−, and 13 [Cr(mal)3]3− (mal = malonate) were synthesized by anion exchange reactions. These compounds were characterized by X-ray powder diffractometry and IR spectroscopy and the results were compared with those of the compounds where X− = F−, 12 CO32−, and NO3−. The IR data allow the significant distinction between hydroxide layer OH-groups forming H-bonds with (i) crystal water and (ii) intercalated anions. With reference to the forces regarding the second H-bonding interaction the following order became obvious: NO3− < [Cr(mal)3]3− < F− ≈ CO32− < mal2− ≈ cis-[Cr(mal)2(H2O)2]−. Propositions of the malonate arrangements in the interlayer were discussed. The malonate ligands of both anionic complexes are situated with an angle of 54.75° to the plane of OH close packing. The found differences between both are assumed to be caused by spatial reasons.

Decomposition of Alkoxysilanes on the Surface of a Hot Wire‐Study of the Decomposition Mechanism

The decomposition of alkoxymethylsilanes (C 2 H 5 O) 4-x Si(CH 3 ) x (x=3, 2, 1, 0) on a hot Mo wire was investigated within the temperature range of 1300-1600 K and at pressures of 12-90 Pa. Within the temperature range 1400-1600 K a rate law of first order was determined. The activation energy of the decomposition of (C 2 H 5 O) 4 Si was estimated to be 74.5 kJ mol -1 . The rate constants k x of the x-methyl-(4-x) ethoxy silane decomposition decreases with increasing x as k 0 :k 1 :k 2 :k 3 ≃9:9:3:1. From these results and the formed products as ethanol and ethene, a surface-activated decomposition mechanism is proposed assuming a two-center reaction of the alkoxy groups with the formed SiO 2 surface on the wire