Nuclear magnetic resonance of binuclear complexes containing a metallacyclopentadiene system

Abstract

A comparative study of the ¹H and ¹³C n.m.r. spectra of complexes [M₂(CO)₆{(HC₂H)₂}](M = Fe, Ru, or Os) is reported. Carbon–carbon coupling constants have been observed for ¹³C-enriched acetylene samples of iron and ruthenium. In the ruthenium complex the T₁ and nuclear Overhauser enhancement (n.O.e.) measurements of the ¹³C nuclei of the organic moiety allowed the calculation of the correlation time for the molecular reorientation; furthermore the T₁ and n.O.e. data for the ¹H nuclei povided an opportunity to estimate the H_A–H_X distance (CH_A= CH_X) in the metallacycle. An improvement in the evaluation of this distance has been gained by measuring the ¹H spinlattice relaxation time in a highly deuteriated sample.