Frederick was the Archbishop of Mainz from 937 until 954. Frederick succeeded Hildebert as the Archbishop of Mainz in 937. From the outset, Frederick was clearly an opponent of King Otto the Great. He took part in the plots of Dukes Eberhard III of Franconia and Giselbert of Lorraine in 939, and was punished with their defeat by a years imprisonment in Hammelburg. In 941 he was implicated in Duke Henry of Bavaria's assassination attempt of King Otto, but managed to avoid punishment by communion and begging for pardon.