Having hosted the latest failed talks, Qatar was already involved in the Iran nuclear negotiations. Qatari Foreign Minister al-Thani promised to remain involved in helping Iran make a nuclear deal. This is not insubstantial, as Qatar remains a close ally to the US, and an advocate to the talks.
Iran sought to clarify its intentions in the process, saying they want to reach a lasting nuclear deal with the US. Such a deal seems possible, but the US has resisted the process.
Iran also sought to clarify what happened at the last talks, denying US claims that Iran is making new demands outside the process. The Iranians wanted assurance of sanctions relief, which they say is not a new thing nor outside of the topic of the nuclear deal.