But, how do you feel as a person to do so? And if you can live with it, do as you feel is right.
This happened to me "one time" but they were not my usual type clients. My clients work with me and understand the amount of work involved to create and complete a real estate transaction. Most people have a good level of integrity and would continue to work with the Realtor that has helped them get to that stage of a transaction.
As noted below, you should consult an attorney regardig your decision.
However there are a few things. If you were NOT unhappy with your agent, just unhappy with the inital offer these buyers made, and now want to sell it to them, why not just relist with your agent, and get the contract drawn up by the buyers agent. After all,even tho there is a zero in the clause, did your agent work for you during the listing period and get you a contract that YOU rejected?
Also, I am assuming the buyers also had an agent, who wrote the initial contract you rejected, so you would be cutting out two agents and their source of income. If you can live with yourself knowing that you did this, then go ahead and sell it to the buyers if your attorney advises you that you aren't liable for commission. But IMHO, I think this stinks.
To be sure you can always have an attorney review it using their free first visit to get some direction. If you do not want to do that just make sure everything is at 0 so you will not owe any commission if sold to this former potential buyer. good luck with your sale