OpenFire and Spark offer secure private chat and collaboration tools
If you're looking to implement a secure, private chat environment in your company, have a look at what's going on at Ignite Realtime with their OpenFire real time collaboration server and Spark cross-platform IM client.
Being that they are open source, both OpenFire and Spark are free; that makes it easy to convince management to give it a try.
But the open source nature of the products also means that if they almost but don't quite suit your needs, you can always modify them to fit the bill.
Ignite Realtime also hosts a number of other related projects including SparkWeb, Smack API, Tinder API, Whack API, and XIFF API. If you're an IT manager or developer looking to implement a secure private chat environment, have a look at OpenFire and Spark.