C5Me4(CH2)3(OCH2CH2)3OMe: a tentacle-bearing cyclopentadienyl ligand and its use in complex chemistry

The reaction of 2,3,4,5-tetramethylcyclopent-2-enone with the Grignard reagent MeO(CH2CH2O)3(CH2)3MgCl 3 affords, after acidic workup, the novel cyclopentadiene HC5Me4(CH2)3(OCH2CH2)3OMe 4, which allows the synthesis of cyclopentadienyl metal complexes that owing to the tentacle function show unusually high solubilities in solvents of all polarities; two such complexes are the ferrocene [Fe{C5Me4(CH2)3(OCH2CH2)3OMe}2]6 and the cobalt carbonyl [Co(CO)2{C5Me4(CH2)3(OCH2CH2)3OMe}]7.