Frederick Rivers, 27, of South Portland, convicted of trying to hire a hitman to

Frederick Rivers, 27, of South Portland, convicted of trying to hire a hitman to kill his wife, was yesterday sentenced to serve 2 1/2 years in prison. In an unusual move the jurors asked the judge to be merciful to him, but while they gave no reason for the request one juror had earlier indicated that he thought police had entrapped Rivers