The 21-year-old McInerney led the Union in scoring with 12 goals in 31 league games last season after scoring eight league goals in 2012. He has one goal in four games this year.
McInerney not yet played for the U.S. national team but was on the winning American team's roster for the group stage of last year's CONCACAF Gold Cup
Wenger, 23, was the first overall pick in MLS's 2012 SuperDraft after winning the Hermann Trophy at Duke. He scored four goals as a rookie and one last season.
Wenger started the Impact's first three games this year during Marco Di Vaio's suspension and has one goal in four matches.
The deal was announced Friday.