Stepwise Reduction of Carbon Dioxide to Formaldehyde and Methanol: Reactions of CO2 and CO2-like Molecules with Hydridochlorobis(cyclopentadienyl)zirconium(IV)

Article abstract of DOI:10.1021/ja00308a019

Stoichiometric reduction of carbon dioxide to formaldehyde and methanol was achieved by using n as the reducing agent.Two steps have been recognized in such a reduction, the first one leading to the formation of formaldehyde and 2O, and the second involving the reduction of formaldehyde to the methoxy ligand in by .The oxophilicity of metal and the high stability of the μ-oxox complex seem to be the driving force of the reaction.This hypothesis and all the steps involved in the reduction of CO2 by the Zr-H functionality have been elucidated by reducing CO2-like molecules with a variable content of oxygen, i.e., R-N=C=O and R'-N=C=N-R'.Carbodiimides insert into the Zr-H bond, forming an amidino ligand which might not be further reduced by the Zr-H bond.Isocyanate inserted into the Zr-H bond, forming formamido ligands which were further reduced by the Zr-H unit to methylamido group by the intermediacy of the imine.The presence of an oxygen on the formamido ligand would explain its reducibility to the imine by the simultaneous formation of the very stable 2O.The structure of the formamidino complex formed from the insertion of C6H4N=C=NC6H4 into the Zr-H bond was determined by an X-ray analysis.Crystallographic details of are as follows: space group P2₁/n (monoclinic); a=17.930(5) Angstroem; b=13.808 (4) Angstroem; c=19.295 (5) Angstroem; β=107.70 deg; V=4551 (2) Angstroem³; Z=8; final R factor was 0.040 for 4915 observed reflections.