Princess Catherine died on 13 March 2007, cf. the death announcement
in Diario El Pais, Montevideo, 17 March 2007 and Le Figaro 24 March
2007, cf. postings at Royals Portal Forum 17 and 24 March 2007. She
has been buried at the Cementerio Los Fresnos de Carrasco.
Dag T. Hoelseth
The above was posted on alt.talk.royalty by Dag Hoelseth. As to a cause of death, HSH Princess Catherine Ivanova was well over 90 years old at her passing. I don't know the cause of death, but certainly her advanced age makes it not unexpected.
I don't know if she was the longest lived of all the Romanov dynasts, but she certainly was one of the oldest. Her parents, as has been noted, were HSH Ioann Constantinovich, who was the oldest son of the famous KR, and Princess Elena of Serbia. With her death, the Constantinovichi are, I believe, extinct, at least in the male line.
Ioann was murdered at Alapaevsk along with Grand Duchess Serge (Ella), Grand Duke Serge Mikhailovich, Ioann's brothers Igor and Constantine, and Prince Vladimir Paley.
None of Ioann's sons had children.
My sincere condolences to her family.