The diversity of structural features in binuclear cyclobutadiene manganese carbonyls: Relationship to homoleptic manganese carbonyls and cyclopentadienyl chromium carbonyls

Theoretical studies predict diverse structural features in the binuclear cyclobutadiene manganese carbonyls (C4H4)2Mn2(CO)n (n = 6, 5, 4, 3). Some such structures are related to experimentally known or low-energy theoretical Mn2(CO)n+4 or (η5-C5H5)2Cr2(CO)n structures. Other (C4H4)2Mn2(CO)n structures contain novel features such as agostic hydrogen atoms forming C-H-Mn bridges or central elongated octahedral Mn2C4 cluster units.