Who married Frederick Augustus, Duke of Nassau?

Friedrich August, Duke of Nassau, Prince of Nassau-Usingen (23 April 1738 in Usingen – 24 March 1816 in Wiesbaden) was the last Prince of Nassau-Usingen and, jointly with his cousin, Friedrich Wilhelm of Nassau-Weilburg, first Duke of Nassau. He died without surviving male issue and was succeeded by his cousin's son, Wilhelm.