[NO3 subset of{(en)Pt(2,2 '-bpz)}(3)]NO3(SO4)(2): Snapshot of nitrate insertion into a cationic Pt-3 metallacycle or simply a packing effect?

The X-ray crystal structure of [{(en)Pt(2,2'-bpz,N4,N4')}(3)](NO3)(2)(SO4)(2)center dot 13H(2)O (3) reveals a NO3- ion sandwiched between pyrazine moieties and oriented roughly perpendicular to the Pt-3 plane, which is in contrast to the in-plane orientation of NO3- when a second anion (ClO4-) is taken up by the Pt-3 metallacycle simultaneously.