The Nets have taken on the contracts of Jack and youngster Sergey Karasev from the Cavaliers in a swap that also has the Celtics acquiring Brooklyn's Marcus Thornton, Cleveland's Tyler Zeller and a protected 2016 first-round pick from the Cavaliers.
"I'm very, very excited. Obviously, playing in New York is a compliment in and of itself," Jack told ESPN's Josina Anderson. "The opportunity to play at the Barclays every night, I couldn't be happier."
Cleveland will take back the draft rights to Ilkan Karaman, Christian Drejer and Edin Bavcic from the Nets to complete the transaction. The moves will give the Cavaliers significant financial flexibility by shedding the contracts of Jack, Zeller and Karasev.
"Jarrett is a proven NBA veteran who will add versatility to our backcourt," Nets general manager Billy King said in a statement Thursday. "The team had a need in that area and we are excited that we were able to secure Jarrett to fill that role. Sergey is a player who we have followed closely for several years. He is a versatile forward and will be a welcome addition to our roster."
Meanwhile, ESPN The Magazine's Chris Broussard reports that the Cavaliers, in addition to James, are also now trying to strike a deal with free-agent guard Ray Allen and/or forward Mike Miller as a means of enticing James even more about a return to Cleveland.
After briefly considering retirement following the Heat's loss to the Spurs in the NBA Finals, Allen is leaning toward returning for a 19th season, sources said.
According to ESPN's Tom Penn, the trade of Jack sheds $9.5 million in salary (Jack, $6.3 million; Zeller, $1.7 million; Karasev, $1.5 million), giving the Cavaliers $21.7 million in cap space.
"I mean, I would've love to stay, but I understand the business side of it. I respect it," Jack told ESPN. "It is what it is, but now I'm looking forward to what I have coming up with the Brooklyn Nets.
Asked if he anticipated being dealt amid reports of the Cavs' interest in bringing back James, Jack said, "With LeBron, they got to do a lot to clear cap space. You know my contract is in the wind of it, so they have to do what they have to do to put themselves in position to acquire somebody like him. Like I said, I understand it."
The two teams revived trade talks shortly after the end of the season with the idea that Jack could be a replacement for Shaun Livingston, who agreed to sign with Golden State in free agency. A league source said the Nets also had a strong interest in Karasev, whom they were high on during the 2013 draft.
Karasev was selected 19th overall, and the Nets took Mason Plumlee at 22nd overall.
Karasev gives the Nets another young forward to develop alongside Bojan Bogdanovic, who has agreed to a three-year deal with the Nets for their mini midlevel exception, according to a source.
The trade can't be officially consummated until Thursday, when a league-wide moratorium on signings and trades is lifted at 12:01 a.m.
Chris Broussard of ESPN The Magazine and Ohm Youngmisuk of ESPNNewYork.com contributed to this report.