The Iranian regime doesn't trust Obama or its admin. One because they believe Obama (along with the Saudis and company) hasn't given up on his original objective of overthrowing Assad. Other is that Obama admin and the US in general are seen to be on the side of Sunnis and particularly Sunni states such as S. Arabia (Iran's main rival in that region). Therefore, by default Islamic State (IS) too, who are sunnis, even if a few members of the Saudi ruling class fear IS might directly attack the House of Saud & other (leaders of) Sheikhdoms in the Gulf region. But until that actually happens, the Iranians would at least assume IS can negotiate with the Saudis & the leadership of the Gulf states. Whereas IS will absolutely not do so with the Iranian regime.
I don't think the Turkish govt for now has a problem with the Kurds in Iraqi Kurdistan. After all, Kurds are relatively a minority ethnic group in the Arab world, and Turkey, should 'push come to shove'.
Iran has a large Kurdish population too. But ethnically the Kurds share deep roots (racially, culturally and linguistically) with most Iranians, and have ALWAYS allied with Iran (even the shia Islamic regime, although Kurds are sunni) when fighting the Arabs or the Turks.
Overall, I think most, if not all, sunni Islamic countries (Arab and Turkish) are reluctant and fearful of taking part or overtly supporting an attack against IS, because many of their citizens are either pro-IS or can become so, should a direct attack take place. Would be hard to contain their own people.
It's a very tricky situation and multi-layered. But a main issue, for now, for the Iranians and to some extent Turks, is that of trusting the motives & intentions of the US and Obama administration in particular.
Its = his admin