It could be that the gradle-2.1 distribution specified by the wrapper was not downloaded properly. This was the root cause of the same problem in my environment.
Look into this directory:
ls -l ~/.gradle/wrapper/dists/
In there you should find a gradle-2.1 folder.
Delete it like so:
rm -rf ~/.gradle/wrapper/dists/gradle-2.1-bin/
Restart IntelliJ, after that it will restart the download from the beginning and hopefully work.