Ring Opening and Carbonylation of the Spiro[2.41hepta-4,6-diene System with TetracarbonylnickelNi(CO),-induced opening of the three-membered ring in spiro[2.4]hepta-4,6-diene (1) is directed by methyl and vinyl substituents. While a methyl group in 1-position hinders the opening of the adjacent three-membered ring CC bond, a vinyl group enhances the opening of this bond. Besides bridged o-alkyl-and o-acyl-x-cyclopentadienyl complexes 2, 5, 6, 9, and 10, dinuclear systems 3 and 7 are also formed, containing a p-[I ,5-di(l-S-q-cyclopentadienyl)-3-pentanone] ligand. Formation of this ligand by carbonylation and coupling of two spiroheptadiene units occurs by coordination of a spiroheptadiene molecule to the acyl complex 2 via the nickelocenophanon 14.

Die durch Ni(CO)4 induzierte Öffnung des Dreirings in Spiro[2.4]hepta‐ 4,6‐dien (Ia) zu (IIa) und (IVa) wird durch Methyl‐ und Vinylsubstituenten dirigiert.

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