Tony Pulis plans to strengthen Crystal Palace's squad and backroom staff in a bid to help the Eagles stay up.
Celtic boss Neil Lennon has refused to name his transfer targets but confirmed he is looking to strengthen his team.
Leonardo has tendered his resignation as sporting director of Paris St Germain and will leave the French champions at the end of August.
The Brazilian informed the board of his decision on Wednesday morning - a week after learning he would be banned for the whole of next season for pushing a referee following a Ligue 1 match in May this year.
The 43-year-old, who took up his post in July 2011 in the wake of the Qatar Investment Authority's takeover of the capital club, will leave at the end of summer transfer window on August 31.
"Leonardo today informed Paris St Germain of his desire to resign from his position as sport director at the end of the current transfer window," a PSG statement read.
"We regret his choice but respect his decision.
"We thank him greatly for his contributions towards the project of building a top European club in Paris and wish him all the best for his future career choice."
The former AC Milan and Inter Milan manager has overseen intense transfer activity in the two years since his appointment, having been tasked with rebuilding the squad in the wake of the Qatari takeover.
During Leonardo's time at Parc des Princes, PSG signed the likes of Zlatan Ibrahimovic, Marco Verratti, Ezequiel Lavezzi, Lucas Moura, Javier Pastore, Thiago Motta and David Beckham - with the Ligue 1 title duly following last season.
Leonardo was also key to the appointment of Carlo Ancelotti as head coach, although the Italian has since left to take charge of Real Madrid.
His influence over new manager Laurent Blanc was always likely to be diluted by the increased ban he received from the French Football Federation (FFF) for allegedly pushing referee Alexandre Castro following a match against Valenciennes on May 5.
Leonardo was initially handed a nine-month ban but, after a failed appeal, it was increased last week to expire on June 30, 2014, during which time he could not be present on the touchline or enter referees' dressing rooms.
PSG have stood by Leonardo throughout, reaffirming their confidence in him and issuing a statement in which they said they "deplored the severity of the new, harsher penalty".
The club announced they would explore future legal options once they had received and studied the wording of the FFF's decision, but those plans are now set to be shelved in the wake of today's announcement.