The organocopper and organocadmium compounds are organometallic derivatives VERY DIFFERENT from the organolithium and Grignard reagents. Their C-metal bonds are much less ionicand the carbon is a much weaker nucleophile.
They are much weaker nucleophiles only capable of attacking very activaated carbonyl groups, like acyl chlorides. The resulting ketone cannot be attacked by these Cu and Cd organometallic reagents.
