Manganese carbonyl fluorides: Are they viable molecules?

摘要

The mononuclear Mn(CO) _5X and binuclear Mn _2(CO) _8(μ-X) _2 manganese carbonyl halides have long been known for the halogens Cl, Br, and I. However, the corresponding manganese carbonyl fluorides (X = F) remain unknown. The structures and thermochemistry of such manganese carbonyl fluorides and their decarbonylation products have now been investigated using density functional theory. In all cases singlet structures were found to have lower energies than the corresponding triplet structures. The expected octahedral structure is predicted for Mn(CO) _5F. Decarbonylation of Mn(CO) _5F is predicted to give trigonal bipyramidal Mn(CO) _4F with equatorial fluorine. Further, decarbonylation gives tetrahedral Mn(CO) _3F. All of the binuclear Mn _2(CO) _nF _2 structures (n = 8, 7, 6) are predicted to have a central Mn _2F _2 unit with two bridging F atoms, a non-bonding Mn?Mn distance of ～3.1 ?, and exclusively terminal CO groups. The thermochemistry of these manganese carbonyl fluorides indicates that they are viable species. This suggests that the failure to date to synthesize the simple manganese carbonyl fluorides arises from a lack of a suitable synthetic method rather than from the instability of the desired products.