The to -the-core Islamic basis of Iran would seem to be totally antithetical to Putin's new found Eastern Orthodox interests plus a Yuge negative vs. the whole Chechnya-Russian history of late. It's got to be petroleum money based antagonism against Sunni SA.
Russia and Iran, keep your friends close, enemies closer, and your Muslim enemies closest. I think that between Syria and Iran there is a balance of power. If Iran gets too cocky, Putin sics Syria on them. If Syria gets to cocky, Putin takes em down and lets Iran have the Muzzies. Iran would love to be secular, IMO the people see themselves as a progressive nation, and a different people than Iraq, the Sauds etc.