Structural control of reactivity in some new cyclidene complexes

The crystal structure of a monoalkylated cyclidene complex of nickel(II) is reported. The asymmetric nature of this structure supports the results of earlier structural work in solution using NMR spectral evidence, and highlights the importance of steric control of the reactions of cyclidene molecules. The crystal structure of a new cyclidene, bearing chiral side chains, is also reported. This species shows extreme selectivity in its reactivity, refusing to alkylate with groups larger than methyl. The lack of reactivity of this cyclidene with the larger alkyl groups is ascribed to the sterically congested nature of the starting material. The structural studies show how careful choice of cyclidene substituents allows for control of the nature of the products of alkylation reactions. © 1998 Elsevier Science S.A. All rights reserved.