In the wake of Trump’s decision to break the Iran agreement, the Iranians are going to be looking for economic and diplomatic support from Putin. Putin, for his part, has no particular reason to love the ayatollahs, but he really hates American financial imperialism, so he will be happy to oblige. He will offer support against the sanctions and make vague threats (not amounting to a clear red line) about what happens next if it appears that the parties are heading for war.
My prediction, of course, is that we are, in fact, heading for war. Will Putin actively intervene on behalf of Iran if that occurs?
No. He will demand concessions from Trump as the price of his neutrality, and he will probably get them.