Electrochemical Behaviour of the Fe ( CO ) 3 NO ° Ion

Polarographic studies have been carried out recently on several carbonyl1 and carhonyl-nitrosyl 2 complexes with the aim of obtaining information on the electronic structure of the M — CO and M — NO bonds. In the reduction of carbonyl complexes the electronic change is localized on a prevailing central metal orbital. In the nitrosyl complexes, however, it is the JTNO 2 orbital which is involved in the reduction process, apart from some cases in which the presence of cr-allylic ligands completely modifies the reduction mechanism giving rise to the cleavage of the M-allyl 'bond 3. This paper reports results on the Fe(CO)3NO e ion, with the aim of comparing its polarographic behaviour with that of the isoelectronic Co(CO) 4 e ion 4 and to find out if in this ionic nitrosyl carbonyl complex it is still the orbital which is involved in reduction.