Moses who quit playing for the Nigerian national team after the 2018 FIFA World Cup is set to sign a deal until the end of the season.
He had arrived in Istanbul on Wednesday to complete all the necessary arrangements.
The 28-year-old has been restricted to five appearances this season at Stamford Bridge, with his only start coming in September during their EFL Cup win at Liverpool.
Moses had arrived at Chelsea from Wigan for £9 million in 2012 and has scored 18 goals in 128 games.
Since joining Chelsea, the former Nigeria international has had loan spells at Liverpool, Stoke and West Ham.(NAN)