if you're using particles then you can create a particle disk cache. Then when you render it wont have an expensive overhead of calculating the particles as well as rendering the scene.
In Dynamics its in Solvers -> create particle disk cache

You can render using the command line which might free up a little memory but if it takes so long for just one frame then it probably wouldnt help.

Other than that I dont really know, if there are any diagnostics mentioned while it attempts to render then post them up.

Simon

p.s, polygon animating is fine