Sandwich compound

As a sandwich complexes in the narrower sense those main group or transition metal complexes are known in organometallic chemistry, carrying two parallel, planar, cyclic organic ligands. These include the metallocene compounds having two cyclopentadienyl ligands.

The first ever synthesized sandwich complex in 1951 was synthesized in parallel by two research groups led by T. J. Kealy and P. L. Pauson and to S. A. Miller, J. A., and J. F. Tremaine Tebboth in different ways as a product of chance ferrocene. Kealy and Paulson actually aimed at the synthesis of purely organic Fulvalens.

Both groups initially came to the same structure proposal, but that could not be reconciled with the analytical data. Specifically, the infrared spectrum of the structure proposed by Kealy should be several signals for the different CH stretching vibrations occur in accordance with the proposal by Fischer and Wilkinson shows the connection but only a single resonance.

The true nature of the ferrocene was eventually replaced by Ernst Otto Fischer et al. and Geoffrey Wilkinson and Robert B. Woodward discovered independently. Wilkinson and Fischer received in 1973 for this achievement and for their lifetime achievements in the field of inorganic chemistry, the Nobel Prize for Chemistry. Robert B. Woodward, 1973 no shareholder of the price was protested in a letter later became known to the Nobel Committee in Stockholm against this disregard of his contribution. However, he had gone back to organic synthesis after the discovery of ferrocene and had been considered for its performance in this area in 1965 with the Nobel Prize.

For a long time the research is mainly confined to the cyclopentadienyl ligands occurring in ferrocene. Later examples are shown for the first time in 1955 by Ernst Otto Fischer and Walter Hafner with benzene ligand bis ( benzene) chromium or 1968 uranocene synthesized with cyclooctatetraene as ligands.

Structure of the Uranocens

Sandwich complexes are used today especially in asymmetric catalysis to obtain pure stereoisomer compounds and exhibit promising approaches for novel semiconducting materials in the form of polymers.

More sandwich complexes

As a half-sandwich complexes are referred to those compounds that have bound only a cyclopentadienyl system via π - bonds to a central metal atom. The saturation of free (electron ) valences for example, passed carbonyl groups.