bond of the substrate is activated by ring strain. Thus, e. 9.. 3,3-dimethylcyclopropene 1 is cyclooligomerized, sometimes highly chemoselectively, on palladium(0) catalysts"! Palladacycloalkanes of various ring size have been discussed as intermediates.We have now succeeded in preparing five-and ninemembered palladacycloalkanes in stoichiometric reactions, and have simulated a catalytic cycle by their thermal decomposition. We synthesized the colorless palladacycloalkanes 3 to 5 by reaction of the dark-red complex (q3-al-0 Verlag Chemie GmhH. 6940 Weinheim. 1982 0S70-083~/82/~101-0064 $ OZ,SO/O Angeu,. Chem. I I~I . Ed. Engf. 21 (19821 No. I

The triphenylphosphenium ion in 1, can be looked upon as a triphenylphosphane complex of phosphorus. 1 is formed by the joint action of Ph3P and AlCl3 on PCl3. Surprisingly, the central P atom in 1 can be protonated; the “ligands” can be successively replaced by more strongly basic phosphanes, so that unsymmetrical triphosphenium ions are also accessible. The length of the PP bond in 1 lies between that of a PP single bond and a PP double bond.

No abstract

Die 'H-NMR-Spektren der Reaktionsldsungen enthalten uberraschenderweise (siehe Molekulstruktur in Abb. 1 !) nur ein Singulett, dessen chemische Verschiebung vom Verhaltnis der Reaktionspartner abhlngt (bei x= 2: 1 : 6 = 1.30 (s); 2: 6= 1.32 (s), 60 MHz, 28 "C, Tolu01)[~~. Die-[**I ~bergangsmetallcarbin-Komplexe, 78. Mitteilung. -77. Mitteilung: E. 0. Fischer, J. Schneider, D. Neugebauer, Angew. Chem. 96 (1984) 814: Angew. Chem. Int. Ed. Engl. 23 (1984) 820. Angew. Chem. 97 (1985) Nr. 3 0 I'CH Verlagsgesellschafi mbH. 0-6940 Weinherm. 1985 0044-8249/85/0303-0215 0 02.50/0

No abstract