Protonenresonanz-spektroskopische Untersuchungen am Chlor-, Brom- und Methylcyclobutadieneisentricarbonyl / A Proton Magnetic Resonance Investigation on Chloro-, Bromo- and Methyl-cyclobutadiene-irontricarbonyl

Proton magnetic resonance spectra including all observable 13C-H-couplings have been measured for chloro-cyclobutadiene-irontricarbonyl.bromo-cyclobutadiene-irontricarbonyl and methyl-cyclobutadiene-irontricarbonyl. The results are discussed with respect to structure and bonding. The structure of a cyclic diene with alternating double and single bonds can be excluded for the four-membered ring of all three compounds. Instead the complex bonded cyclobutadiene contains an electron distribution of higher symmetry with — despite the influence of the substituent — nearly uniform bond orders.