The sulfate anion, that's the yellow sulphur atom bound to four red oxygen atoms, has a charge of minus two. The perchlorate anion has a charge of minus one. So my guess is that there are twice as many perchlorate anions in nickel hydrazine perchlorate that use an oxygen to oxygen bond, like you find in hydrogen peroxide, bonding adjacent perchlorate anions, IMHO, so that the net charge of the molecule is zero. (The pale green Ni atoms are nickel. The dark blue N atoms are nitrogen. The unmarked dark atoms bound to nitrogen are hydrogen.)
What Is A Coordination Compound?
Perchlorates can be very strong oxidizing agents, e.g. The mixture of a perchlorate and any organic material may result in explosion that may be touched off by friction...