Too late for the 645 election.

As Bob quoted from the instructions:

When To File
File the election by the due date (including extensions, if any) of the Form 1041 (or Form 1040-NR, if applicable) for the first tax year of the related estate (or the filing trust). This applies even if the combined related estate and electing trust(s) don't have sufficient income to be required to file Form 1041.