I've been debating turning my pcl5 into thionyl chloride to avoid producing pocl3 when I need things chlorinated. The only reason I have to keep pcl5 is for vilsmeier which I haven't done in months
Personally, I would recommend keeping it as PCl
5 and only synthesizing SOCl
2 when you know you'll need it sometime in the next reasonable amount of time. It's a bit of a pain to purify the SOCl
2 POCl
3 mixture to perfection, but having SOCl
2 handy when the time comes to use it is really nice. It is subject to photolysis and slowly degrades and is all around nasty stuff so I, too, prefer keeping PCl
5 in storage than thionyl chloride.
The synthesis is very visually appealing though. Colorless gas + colorless solid -> colorless liquid. Very cool to see.