It is Not true. No marriage took place between Umar and daughter of Imam Ali (AS). Fabricated narrations in this regard have been refuted by authentic evidence. Allama Nassir Husain son of Allama Haamid Husain has written a full book ( إفحام الأعداء والخصوم) in which he has mentioned authentic evidence that the whole story of the claimed marriage was fabricated by the enemies of Ahlul Bayt then mentioned by Ibn Sa'd in his book al-Tabaqaat. Ibn Sa'd was pro Umayyad rulers.

'Wassalam.