This work was supported by the National Sciences and Engineering Research Council of Canada's-Strategic Energy Grants Programme. F. H. acknowledges the French-Canadian Cultural Exchange Programme for assistance with his research leave at the University of Toronto. L. F. N. thanks NSERC for a graduate fellowship during her research work. We especially wish to thank Dr. W. Pearce and Dr. J. Daniels, Toronto, for the use of their magnetic and Mössbauer euipment and for their invaluable advice.
The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 898. DOI:10.1002/anie.198308980