Zirconium tetrachloride-formaldehyde sigma-complexes: A computational and spectroscopic investigation

We have carried out a combined theoretical-experimental study of the structures and energies of ZrCl(4)-aldehyde complexes using (13)C NMR spectroscopy and a DFT (B3LYP) computational approach. The computational investigation has demonstrated the existence of different types of complexes: a 1:1 complex (H(2)CO-ZrCl(4)), various 2:1 complexes ((H(2)CO)(2)-ZrCl(4)), and several dimeric species. The analysis of the energies involved in the formation of the various complexes has indicated that the dimeric species should correspond to the only adduct observed in the (13)C NMR spectra (carbonyl resonance at 226.96 ppm) when a 1:1 ZrCl(4)/aldehyde molar ratio is used, while the 2:1 complex should be responsible for the signal at 224.30 ppm that is recorded when this molar ratio is 1:2.