The midfielder, 25, was close to penning a deal at the Ricoh Arena on Friday after the Sky Blues agreed a fee with Norwich, with Clingan apparently keen to seal the move. However, his agent has reportedly since got involved and made demands that have put a block on the deal going through.
"I thought we had one towards the back end of last week but, agents being agents, that has changed," Coleman told the Coventry Telegraph. "We have said all along, the chairman and I, that we will not bend over for agents.
"Agents' fees and stuff like that has stopped us signing a good player, and a player we have chased for two months.
"We have not had one conversation with the agent, we have done it all through the club, who obviously hold the registration of the player. Then at the last minute we got a call from the agent asking for a ridiculous fee, despite the fact that he has done no work whatsoever, and we said no.
"The deal is dead in the water at the minute, so we are going to have to look elsewhere."