12 Just as Boniface was dear to St. Gregory II for the eminence of his virtue and his burning zeal for the spread of Christ's kingdom, he was likewise to his successors: namely, to Pope St. Gregory III, who, for his conspicuous merits, named him archbishop and honored him with the sacred pallium, giving him the power to establish lawfully or reform the ecclesiastical hierarchy in this territory, and to consecrate new bishops "in order to bring the light of Faith to Germany;" to Pope St. Zachary also, who in an affectionate letter confirmed his offlce and warmly praised him; finally, to Pope Stephen II, to which Pontiff shortly after his election, when already coming to the end of his life's span, he wrote a letter full of reverence.
Source: Ecclesiae Fastos (Vatican.va)