The move for the Centurions comes as the club seek to avoid relegation from the English Super League, a competition they currently sit bottom of the table in, having not won in their 13 starts.
The Centurions were only promoted to the top flight of English rugby league ahead of this season.
Neither Macdonald or Stone have been overly busy with NRL duties. Macdonald, who has previously played for the Titans, Dragons and Cowboys, is currently in the Sharks' set-up.
The outside back, who has scored 35 NRL tries in 98 appearances, is yet to register a game this season in first grade, and only made it onto the park twice last year for the Sharks.
It followed an exit after two strong years at the Dragons, with a short stint at the Cowboys in between.
Macdonald has all the tools to succeed in the English Super League however, with height and speed on his side.
Stone, on the other hand, at just 23 years of age, has struggled to break into the Titans' first grade side. The second rower made 18 appearances for the Knights before switching to the Titans, where he didn't play his first game this year until Round 11.
Leigh will travel to play Hull FC this weekend, desperate for a victory.