Hmmm, iPhone 4S is bluetooth 4, not 2.1. There is an issue with the 5's - that causes all sorts of issues including delayed microphone connection, spotty connection, failure to recognize some bt devices. Seems it could be a hardware issue as not everyone is experiencing the problems.
I had the same question dealing with connecting ip5 to mid - 2012 MacBook Air and turns out Apple doesn't want you to connect and transfer like that. Please see the attached screen capture of macrumors community explaining this.