1	NFR	Ni-Fe reduced active center	1.000
2	NFU	Formyl[bis(hydrocyanato-1kappac)]ironnickel(Fe-ni)	0.778
3	FNE	(mu-sulphido)-bis(mu-cys,S)-[tricarbonyliron-di-(cys,S)nickel(II)](Fe-ni)	0.700
4	NFO	Ni-Fe oxidized active center	0.700