Fans had been inside the ground for up to eight hours when it was announced that the final would be postponed until Sunday (8pm GMT).
Former Manchester United, Juventus and Manchester City striker Carlos Tevez was one player affected by the tear gas.
Tevez complained that his side were not fit to play the game, having been exposed to tear gas.
Boca eventually agreed to play, but kick-off was delayed by two and three-quarter hours and it was clear they were playing under protest.
"They were throwing pepper gas, stones, everything", Clarin website quoted Juan Carlos Crespi, a member of the Boca delegation, as saying.
Further reports suggest that the driver of the Boca Juniors bus almost collapsed upon arriving at the Monumental due to the effect of the gases, while some of the players were said to be vomiting, with Tévez, Wanchope y Espìnoza among the worst affected.
Just minutes before the delayed kick-off, the teams had still not warmed up on the field.
"They're forcing us to play this game under these conditions where we have teammates who are not well", Tevez told reporters outside the locker rooms.
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"He said the game shouldn't go ahead tomorrow & suggested that CONMEBOL want to give the trophy to River".
Photos showed Boca captain Pablo Perez with his eye bandaged after being taken to hospital and other players suffered cuts to the face, arms, legs and chest.
Dominguez met with club directors and FIFA President Gianni Infantino.
Footage also emerged of the Boca bus approaching the stadium at high speed, trying to avoid the barrage from the River Plate fans.
As time drifted by and delay added to delay, it came to seem increasingly that the match, billed as the derby to end all derbies, would never start.
Argentinian football has a long history of violent incident which has resulted in away fans being banned from games. The tie is evenly poised following an entertaining 2-2 draw in the first leg at Boca's stadium, La Bombonera, last week.
The game was taking place at River's Estadio Monumental, where most of the 70,000 fans with tickets were already in place when the violence occurred.
This local encounter is widely viewed as the fiercest rivalry in world football.