Complex sentence: Nabokov's son Dmitri Nabokov and wife Vera Nabokov became his literary executors but could not bring themselves to destroy Nabokov's final work, and so it was placed in a Swiss bank vault where it has remained since his death.
Split into simpler sentences: Nabokov's son Dmitri and wife Vera Nabokov became his literary executors but could not bring themselves to destroy the final work. They placed it in a Swiss bank vault, where it has remained since his death.