In [Fe(H2O)5NO]2− and [Fe(H2O)5NO]3− , the unpaired electron present in higher energy anti bonding MO of NO transfers to lower energy t2g orbital of Fe still these contain unpaired electrons and are paramagnetic . In [Fe(CN)5MO]3− , the unpaired electron in higher. Energy anti bonding Mo of O cannot go into the higher energy eg orbital of Fe as there is no vacancy in lower energy t2g orbital. so it remains in NO and as a whole the complex is paramagnetic. in [Fe(CN)5NO]2− the electron from NO can be transferred to vacant energy t2g orbital. Since all the electrons are paired in this complex it is diamagnetic.