The Cameroon international joined Barcelona last week in a deal in the region of £15m to become the Gunners' second high-profile departure of the summer alongside Robin van Persie's move to Manchester United.
Song told The Sun: "I was ready to commit my future to the club. All I wanted were talks about a new contract but each time we were due to sit down, the club postponed it. I was fobbed off. I wanted a new five-year contract at Arsenal. In the end I got one - at Barcelona.
"I had been trying for eight months to start talking about a new long-term deal but the club kept postponing me all the time, saying 'You have three years left'.
"I hadn't talked about money I just wanted to sit down and discuss a new deal - I wanted to commit my career to the club I loved."
The 24-year-old could reportedly make his debut for the Catalan giants against Osasuna.