I suggested nitrogen-phosphorus based life as alternative to carbon. Go to:

My ideas about complex inorganic life

and see the links I put. I made all in powerpoint.

But I'm making a second version of such idea and I'll put that in a new topic, because the second version is better than the first.

And It's more organized.

I think that nitrogen-phosphorus based life also could use carbon for some function. This kind of biochemistry would work well at planets with lower temperatures, and in a reducing atmosphere and in oceans of ammonia or aqua-ammonia. Oxygen to such organisms would be lethal. The atmosphere would be rich in nitrogen, methane or ammonia or any other reducing gas.

Silicon-based life to me is much less versatile than a combination of nitrogen and phosphorus. Silicon and oxygen are too stable, at least in room temperature to allow the formation of any organism.

To me, nitrogen-phosphorus or boron-nitrogen substances are more reactive than carbon-based complexes. And if they are more reactive, they would work well in lower temperatures, allowing metabolism in cold worlds. Their metabolism world be almost as fast as ours, due to such substances.

In the new version you'll also find complex compounds of nitrogen and boron, that could also form orgasnisms. And complex compounds of sulfur too.