The White Sox and Diamondbacks have agreed on a trade that will send starting pitcher Edwin Jackson to Chicago, the first potential step in a deal that could send Nationals first baseman Adam Dunn to the White Sox and land Jackson with the Nationals. The Nationals are intent on either trading Dunn or signing him to a contract extension by Saturday's 4 p.m. non-waiver trade deadline. As of now, Dunn heading to Chicago remains only speculation. But the White Sox have pined for Dunn for some time, and Nationals General Manager Mike Rizzo has shown interest in Jackson.