Al-Hasan (may Allah have mercy on him) said that the Messenger of Allah (peace and blessings be upon him) said: "The divorce of a woman with whom the marriage has not been consummated is one."
This is mursal, and its narrator Sulayman bin Arqam is da'if (weak).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 15089