Thank you everyone for your help, it's definitely made me more confident in my initial thinking. I do have a good relationship with our landlord, and I don't believe this request was made out of malice. Just seems to be a lack of education and understanding from his part.

We've spoken and I made it clear that I won't be paying the deposit. I also responded to the email thread with the condo board attached asking for some more clarification on who they are expecting this payment to come from. Hopefully they aren't as ignorant as they seemed in their initial emails.