As the sun began to set that Wednesday night, Mayo Shattuck huddled with the rest of his management team and reviewed their last, desperate options to buy their company one more day.

Shattuck, the chairman, chief executive officer and president of Constellation Energy Group, and other top executives had spent that frantic day of Sept. 17 dashing between boardrooms at their headquarters, trying to cut a deal that would give the company the cash it needed to avoid bankruptcy.