Hi, I was wondering if someone could help me out with the aforementioned compound. I was meandering my way through wikipedia while at work today, and I came across nitroprusside (http://en.wikipedia.org/wiki/Nitroprusside) while in the hemoglobin article.

The article lists the molecule as a dianion, but I can't for the life of me find where the negative charge(s) should be on the molecule (in fact, it looks like there are two positively charged atoms there -- the nitrogen and oxygen of the nitric oxide group). I am usually pretty good with strictly organic molecules, but bio-inorganics are somewhat unfamiliar to me. I'm guessing it will have to do with the iron atom, but I am really just speculating. There is an image at the wikipedia article.

Okay, so it's on the Iron. But what about the positives?

Any explanations?

The iron has a charge of +2, the NO ligand has a charge of +1, and each of the five cyanide groups has a charge of -1. So you have 5 units of negative charge and three of positive, giving you -2 overall.

That makes sense, thanks Nasor. I was treating the bonds between the ligands and the iron as proper covalent bonds, which would eliminate the negative charges on the cyanide ligands and create a positive one on the nitrogen of the nitric oxide ligand.

I swear to god!!! Every time I see this thread I think it says Nitropussy. Who names these things?!

It derives from Prussia, see link.

http://en.wikipedia.org/wiki/Prussia

Most likely the name originated because of the invention of the pigment Prussian blue, a compound of certain iron oxidation states with cyanide. Hydrogen cyanide has also been known as Prussic acid.

http://en.wikipedia.org/wiki/Prussian_blue