Organochromium π-complexes—VIII. Reactions of the (η5-Me5C5)Cr-system with 1,3-dienes and alkynes ☆

Abstract Cp*(η 4 -1,3-diene)Cr compounds have been prepared either by reacting Cp*(η 3 -C 3 H 5 ) 2 Cr with a diene or by reducing Cp*Cr(THF)Cl 2 with activated-Mg in the presence of the diene. These coordinatively and electronically unsaturated species readily form adducts with CO or P-donor ligands. The reaction of Cp*(η 4 -1,3-C 4 H 6 )Cr with further butadiene leads to the formation of Cp*(η 3 ,η 3 -octadienediyl)Cr which in turn reacts with a disubstituted alkyne (RC 2 R) with addition to the 2,7-positions of the octadienediyl chain to give Cp*(η 1 ,η 2 ,η 1 -R 2 C 10 H 12 )Cr species. The crystal structures of representative compounds have been established by X-ray diffraction.