The listing agreement and the buyer/broker agreement are both agreements between the client and the broker, not the agent. This means that unless your client and the broker agree otherwise, the deal stays with the brokerage when you leave.

The Independent Contractor Agreement that you signed when you began working at the brokerage will govern what happens to your commissions when you leave with pending transactions. Whether your old broker agrees to release the listing or not, your Independent Contractor Agreement will dictate if and how compensation will be paid for any pending transactions you may have.