Florence was nominally an Imperial fief, and Siena a Spanish one. The plan was about to be approved by the powers convened at Geertruidenberg when Cosimo abruptly added that if himself and his two sons predeceased the Electress Palatine she should succeed and the republic be re-instituted following her death. The proposal sank, and was ultimately put on hold following Emperor Joseph's death. Charles VI, Holy Roman Emperor, agreed to an audience with the Electress Palatine in December 1711. He concluded that the Electress's succession brought no quandary, but added that he must succeed her. Cosimo and herself were abhorred by his reply. Realising how unforthcoming he had been, Charles wrote to Florence agreeing to the project, mentioning but one clause: the Tuscan state must not be bequeathed to the enemies of the House of Austria. At the culmination of the War of the Spanish Succession, at the Treaties of Utrecht and Rattstatt, Cosimo did not vie for international assurances for the Electress's succession. An inaction he would later grow to lament. The Grand Prince finally succumbed to syphilis on 30 October 1713. Cosimo deposited a succession bill in the Senate, Tuscany's nominal legislature, on 26 November. The bill promulgated that if Gian Gastone predeceased the Electress Palatine, she should ascend to all the states of the Grand Duchy. It was greeted with a standing ovation by the senators. Charles VI was furious. He retorted that the Grand Duchy was an Imperial fief, and that he alone had the prerogative to choose who would succeed. Elisabeth Farnese, heiress to the Duchy of Parma and the second wife of Philip V of Spain, as a great-granddaughter of Margherita de' Medici, exercised a claim to Tuscany. In May 1716, the Emperor assured the Electress and the Grand Duke that there was no insurmountable obstacle preventing her accession, but that Austria and Tuscany must soon reach an agreement regarding which royal house which was to succeed the Medici. As an incentive to accelerate Cosimo's reply, the Emperor hinted that Tuscany would reap territorial advancements. In June 1717 Cosimo declared his wish that the House of Este should succeed. Charles VI's promises never materialised. In 1718 he repudiated Cosimo's decision, declaring a union between Tuscany and Modena (the Este lands) unacceptable. On 4 April 1718 England, France and the Dutch Republic (and later Austria) selected Don Carlos of Spain, the eldest child of Elisabeth