Turkey has become an Iranian ally politically and millitarily. They also do alot of trade with Iran so sanctions are not in their best interests either so if they can come to some kind of arrangement with Iran for image purposes only to at least delay the sanction talk then they it suits them both. Turkey is also an islamic state that is slowly becoming more radicalized and Iran would love to encourage that. This little deal is to do nothing but delay sanctions , its not going to slow things down for Iran but their nuclear program will continue both sides know it but neither side says it on the record. Don't anybody break out the champagne yet because this isn't an end to the Iranian nuclear problem its just another delaying tactic.
Rocket alarm sirens sound in southern Israel (Haaretz)
from the article: Why does Iran see Turkey as an 'honest broker' for a nuclear deal?