Thanks for taking a look, but I have figured this one out finally. I was making a very simple error that was throwing off my answer. If anyone else is having trouble with a similar problem, this is how I came to my answer:
Quick note--I had not originally given that the Cl2 and 2Cl were in the gaseous state.
To solve, I first converted my :delta:H/mol to J/atom and used this energy as the work function. Then I just plugged in the numbers and solved for wavelength by rearranging the equation w= h * (frequency), which gives:
[lambda] = (c*h)/w
Then all that was left was to convert from m to nm.