A monoclinic 1-platinum defect recently detected was investigated more thoroughly by electron paramagnetic resonance ͑EPR͒. The defect is one of the dominating defects in platinum doped silicon. With a perfect reproducibility it is observed in samples prepared from n-type silicon as well as from p-type silicon, in float zone ͑FZ͒ silicon as well as in Czochralski ͑Cz͒ silicon. Its concentration varies with the conditions of preparation and nearly reaches that of isolated substitutional platinum in Cz silicon annealed for 2 h at 540°C after quenching from the temperature of platinum diffusion. Because of its concentration which in Cz-Si exceeds that in FZ-Si the defect is assumed to be oxygen-related though a hyperfine structure with 17 O could not be resolved. The defect causes a level close to the valence band. This is concluded from variations of the Fermi level and from a discussion of the spin Hamiltonian parameters. In photo-EPR experiments the defect is coupled to recently detected acceptorlike self-interstitial related defects ͑SIRDs͒; their level position turns out to be near-midgap. These defects belong to the lifetime limiting defects in Pt-doped Si.

rnBei der Umsetzung von Cyanharnstoff rnit o-Brom-acetophenon oder einigen p-substitutionsprodukten entstehen in AbhBngigkeit von den Reaktionsbedingungen 4-substituierte 1 -Cyanimidazolone-(2) 1 bzw. 5-substituierte 2-Amino-oxazole 8. Der nucleophile Angriff des ambidenten Cyanharnstoff-Anions auf die polarisierte C-Br-Bindung der cc-Bromketone erfolgt also in beiden Fallen iiber das N-Atom. Die I-Cyan-imidazolone-(2) lassen sich leicht zu 1 -Carbamoyl-imidazolonen-(2) 3 bzw. unter gleichzeitiger Decarboxylierung zu Imidazolonen-(2) 2 verseifen. -Setzt man bei obiger Reaktion die doppelte Menge Cyanharnstoff ein, so erhalt man mit den u-Brom-acetophenonen sowie rnit 2-Brom-butanon, or-Brom-propiophenon und Desylbromid die entsprechend substituierten l-Cyanguanyl-imidazolone-(2) 4.

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KONINK LIJKE/SHELL-LABOR ATOR UM, AMSTERDAMThe syntheses of the five methyl-cis-bicyclo[3.3.0]octanes are described. The exo-3 compound could only be obtained as a mixture with an equal amount of its endo-3 isomer. IntroductionIn the course of our investigation into the isomerization of perhydroindane 1 we required authentic samples of the five methyl-cis-bicyclo[3.3.0]-octanes for identification purposes.A literature search revealed that none of the isomers, I-, endo-Z, exo-2-, endo-3-, and exo-3-methyl-cis-bicyclo[3.3.0]octane had been described before. Mair et a1.2 have demonstrated the presence of only one of them in petroleum, but could not establish its spatial configuration.

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