Believe you have it backwards. The Patriarch of Constantinople. Michael Cerularius, caused the rift when he rejected accepted theology and altered the Nicene Creed. Incidentally, the Great Schism was not the first break from the church as an earlier one occurred Circa 400 AD with the establishment of the eastern Asyrian church.
Actually, you have it backwards my friend. The filioque clause was inserted into the Nicene creed at the Third Council of Toledo in 589. It was rejected by all popes (bishops of Rome) from then until 1014, when Pope Benedict VIII officially inserted it under heavy pressure from Henry II, the Holy Roman Emperor.
This contributed to (but wasn't the only factor in) the Great Schism of 1054. Pope Leo IX sent Cardinal Humbertus of Silva Candida to Constantinople to reach an agreement with the Eastern patriarchates, but the Cardinal instead excommunicated Michael Celarius, the Patriarch of Constantinople. In return, the Patriarch excommunicated Humbertus.