Can not share files over airdrop between iPod touch and Mac mini
Can not share files over airdrop between iPod touch 5 th gen with iOS 8.4 and Mac mini (Mid 2011) Yosemite 10.10.2
Your Mac is too old. For AirDrop between a Mac and iOS device the Mac has to be:
Your Mac needs to be a 2012 or later model with OS X Yosemite installed*
Use AirDrop to send files from your Mac to another nearby Mac or iOS device - Apple Support