The boss often tries to impute his mistakes to the people who work under him.
The boss is always trying to blame everyone else for his failures.
impute を使って言うなら次のように言えます。
ーThe boss often tries to impute his mistakes to the people who work under him.
「その上司は、よく彼のミスを部下になすりつけようとした」
to impute one's mistakes to ... で「…にミスをなすりつける」
次のように言った方が自然です。
ーThe boss is always trying to blame everyone else for his failures.
「その上司は、いつも彼の失敗をみんなになすりつけようとする」
to blame ... for one's failures で「失敗を…になすりつける・…のせいにする」
ご参考まで！
カナダ 
