Metal ion interactions with Mn(CO) −5 in ether solutions

Abstract

Infrared spectra of LiMn(CO) 5 and NaMn(CO) 5 in the CO stretching region have been examined in ether solvents. These spectra are attributed to an ion-paired species of C 3ν symmetry in which alkali metal ion is bonded to carbonyl oxygen. Simple force constant calculations yield CO stretching force constants which are reasonable in terms of the structure hypothesized. In THF the NaMn(CO) 5 spectra show the presence of an equilibrium between solvent-separated and contact ion-pairs. Treatment of NaMn(CO) 5 in THF with Mg 2+ gives a species whose IR spectrum is also consistent with a MgOC interaction. Mixtures of LiMn(CO) 5 or LiCo(CO) 4 with CH 3 Li in ethyl ether were examined at −50° using 7 Li NMR. Only resonances due to the pure components were observed, indicating that no mixed tetrameric species of the form Li 4Me n - X 4− n are formed.