Industrial gas producer Airgas filed suit against Cravath, Swaine & Moore on Friday over the firm’s role as legal adviser to rival Air Products on that company’s $5.1 billion bid for Airgas.

Air Products announced on Friday its unsolicited offer for Airgas, which for months has resisted entreaties from its larger rival, including rejecting an October offer whereby Air Products would assume $1.9 billion in Airgas debt. The New York Times reports that by making its offer now, Air Products hopes to capitalize on what it perceives as current weaknesses in Airgas’ financial health.