Analogies between binuclear phospholyl and cyclopentadienylmanganese carbonyl complexes: seven-electron donor bridging phospholyl rings†
Abstract
Phosphacymantrene, (η5-C4H4P)Mn(CO)3, is a known stable compound and a potential precursor to binuclear (C4H4P)2Mn2(CO)n derivatives analogous to isovalent (C5H5)2Mn2(CO)n derivatives. In this connection the structures and energetics of binuclear derivatives have been investigated by density functional theory. The lowest energy (C4H4P)2Mn2(CO)n (n = 5, 4) structures have seven-Mn triple bond of length 2.17 Å analogous to (η5-C5H5)2Mn2(μ-CO)3, which has been synthesized and structurally characterized by
Mn triple bond of length 2.20 Å. The two analogous singlet (η5-C4H4P)2Mn2(CO)2 structures have shorter Mn
Mn bonds of length 2.07 Å, which are interpreted as the formal quadruple bonds required to give each Mn atom the favored 18-electron configuration.