Looks like the torque rod that limits transmission movement by securing it to the cars frame. You should tighten that bolt. Actually, you should replace the bushings on it, then bolt it back up. Which reminds me, I should check on mine lol.
Front Torque Bar:
- Engine does not need to be supported from below for this part of job
- Remove bolt securing bar to front cross-frame (long profile wrenches needed)
- Remove bolt securing bar to transmisison bracket
- Remove bar and install new
- Torque for bolt at transmisison end is 35 ft-lbs
- Torque for bolt at front cross-frame end is 90 ft-lbs (why long wrenches are needed!)
Saab doesn't sell the bushings separately, but you can get a Powerflex bushing to replace the large one that's pushed way over to one side in your picture. It costs about the same as getting a new Hutchinson torque rod, which is the OEM. The smaller bushing that your loose bolt goes through doesn't tend to fail nearly as often.
Powerflex (at least in the UK) do three versions of the rectangular bush, normal, harder, and track day. I can't access the site right now so can't verify. I was able to push mine out with two thumbs (at 135K miles) but it needs force to put the new one in of course. I took the arm out to do it in a vice but I suppose a G-clamp under the car might work. I found (manual gearbox) that a bracket has to be loosened to back out the forward bolt.