I did much better when I did about 4 workouts a week-2 light and 2 heavier, and set an absolute 45 minute time limit.
Something like this
Day 1 Light-Chest, Upper back, Biceps, Triceps
Day 2 Light-Legs, shoulders, abs, calves or hams
Days 3 and 4 were the same split, but heavier and with different (more power type) exercises). Start with just 3 sets of 1 exercise for each bodypart.
I may have even done better combining days 3 and 4 and sticking to the basics
Pulldown or Row
Alternate DB Curl
Leg press or squat
Lying leg curl
Dumbell shoulder press
Hanging leg raise
For days 1 and 2 pick a weight that you could get 15-20 reps on with an all out effort. Do three sets.
If you get 20 reps on the first set, raise the weight next time.
Day 3 and 4 combined version
Use your 5-6 rep max and do three sets. When you can get 3 x 5 raise the weight.
These three days should be split over the week so M W F would be fine.
Make it quick. It's 12 sets a workout and you get 45 minutes which should be easy. When you can get it done in 25 minutes, you can add a set or eventually 2 sets of each, and every 3-4 weeks drop down to just 2 sets but try to push to the maximum-so eventually you will be doing
3 sets each
4 sets each
(Maybe 5 sets each)
2 sets each pushing to the max with a little more rest between sets.
Just suggestions. Also, I would definitely combine a couple of gatoraides with 60+ grams of protein and a LOT of water and take it with you to work-use a gallon container. In 6 hours of non-exertive time you probably could use close to 60 grams of protein. If you can do this, the extra work can make you grow and get you in great shape.
Will you be able to sleep immediately after work, or in the afternoon?