Here's the offical release from the Reds:
REDS TRADE DUNN TO DIAMONDBACKS
Receive Three Players From Arizona
CINCINNATI - The Cincinnati Reds today acquired from the Arizona Diamondbacks RHP Dallas Buck and 2 players to be named later in exchange for OF Adam Dunn and cash.
Buck, 24, this season went 1-4 with a 3.94 ERA in 9 games and 8 starts with Class A South Bend. Last Monday he was promoted to High Class A Visalia and made one appearance, pitching 5.0 shutout innings Thursday vs San Jose. He will be assigned to Class A Sarasota.
Buck was selected by Arizona in the third round of the 2006 first-year player draft. He attended Oregon State University, where he was a member of the 2006 NCAA national championship team. He made his professional debut last season by going 4-4 with a 3.41 ERA in 16 starts with Visalia.
Dunn batted .233 with 32 home runs and 74 RBI in 114 games with the Reds.
The Reds have not announced who will replace Dunn on the 25-man roster.