rhododendron

If the branches are brittle then they are dead. Is there any live wood on the shrub? Where and how are you trying to grow the rhododendron?

yes their is live wood in ericaceous compost in the garden

I'd prune off all the dead wood - and take it from there. Make sure the rhodo is planted is semi shade and that it is getting watered if it is a new shrub this year.