/bin/sh: 1: Syntax error: EOF in backquote substitution
The problem is that cron treats % as newlines. From crontab POSIX man page:
Percent-signs (%) in the command, unless escaped with backslash \, will be changed into newline characters, and all data after the first % will be sent to the command as standard input.
Also use Command Substitution syntax as $() over the legacy `` syntax as
You could change your command to something like,
*/2 * * * * mongodump --db prodys --out /backup/databases/mongoDatabases/$(date +'\%m-\%d-\%y')