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A sandwich in a sandwich: Electrophilic double-sandwich compounds are readily formed by interaction of ferrocene and nickelocene with the tridentate Lewis acid 1 (see scheme; C gray, F light green, Hg orange, M dark green). These new supramolecules result from π interactions between the mercury centers of 1 and the C5H5 rings of the metallocenes. Surprisingly, the nickelocene derivative is dark red and air stable.
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Haneline et al. (2004) studied this question.
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