Synthesis and X-ray structure of an unexpected bidentate allene–aminocarbene complex of tungsten

This contribution describes the results obtained from the alkylation reaction upon base-induced of propargyl bromide at nitrogen of Ferrocenyl-N-pentylaminocarbene of tungsten, chromium and molybdenum. This led to unexpected highly strained Fischer-type carbene complexes (5a–c) containing a bidentate allene–aminocarbene ligand. This is the first report of the η2-allene Fischer carbene complexes. The structure of 5a was confirmed by an X-ray diffraction analysis.