The S-300 is an air-defense system. If Israel is lucky, it will refrain from attacking Iran which is beyond its power anyhow. There are too many nuclear installations in Iran, which will require many sorties and a need for midair refueling (where?). And an attack will not go without a response, also against the US. Netanyahu, just forget this dream and leave the matter to the US and its allies. So far, we see progress in tightening the screws around Iran's neck.
U.S. confirms ISIS computer expert killed in air strike (Reuters)
from the article: Russia says in talks with Iran on new nuclear plants