Schumacher, Ernst

Dedicated to professor Ernst Schumacher on the occasion of his 75th birthday. 

The possibility that a cationic species of the general composition [M2(C5H5)3] + could exist, was first mentioned in a paper published in 1964 [2]. Ernst Schumacher and Richard Taubenest, at that time at the University of Zurich, reported that the ions [Fe2(C5H5)3] + and [Ni2(C5H5)3]+ can be generated from ferrocene and nickelocene in a mass spectrometer under appropriate conditions. The authors concluded that the precursor molecules, after being transformed to the... 

In retrospect, it is ironic to it that when I met Ernst Schumacher in 1969 (he was then Professor at the University of Bern in Switzerland) we did not talk about the experiments he did at Zurich in the same building where I was at that time. Instead, his interest focussed on our work on borazine transition metal compounds and we discussed in some detail whether it would be possible to incorporate metal atoms like chromium or molybdenum between the layers of hexagonal boron nitride (BN) in a similar way as it can be done with graphite. In the course of these discussions I did not mention that, after I had moved to Zurich, we had begun to investigate the reactivity of nickelocene towards both nucleophilic and electrophilic substrates. The reason was that we were still at the beginning, and while we had been able to prepare a series of monocyclopentadienyl nickel complexes from Ni(C5H5)2 and Lewis bases, our attempts to obtain alkyl- or acyl-substituted nickelocenes by the Friedel-Crafts reaction failed. 

It is a pleasure to acknowledge the support of this research by the National Science Foundation. Helpful discussions with Ernst Schumacher, Ernest Davidson, and W. C. Stwalley are gratefully acknowledged. 

Fritz Blatter and Ernst Schumacher, J. Chem. Educ., 67,6 (1990)... 

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