Alkynyldicobalt Derivatives of Dibenzosuberenol and Dibenzocyclooctatrien‐5‐ol: Ring Conformations, Ease of Carbonyl Elimination and Relevance to Pauson–Khand Cyclization

Under very mild conditions, (5‐alkynyl‐5 H ‐dibenzo[ a,d ]cycloheptatrien‐5‐ol)Co 2 (CO) 6 clusters 1 lose a carbon monoxide ligand and form the corresponding η 2 ‐alkene‐µ‐alkyne‐Co 2 (CO) 5 complexes 2 (the first isolated examples of the initial phase of the Pauson–Khand reaction). This behaviour is not paralleled by the homologue in which an additional methylene group has been inserted within the seven‐membered ring, as in the [5‐alkynyl‐6 H …