Stabilisation of the [Mn(CO)(2)](+) fragment by thioether macrocyclic ligands; synthesis, spectroscopic and structural characterisation

摘要

The fac-tricarbonyl manganese(I) species fac-[Mn(CO)(3)(L)](+) (L = [12]aneS(4), 1,4,7,10-tetrathiacyclododecane; [14]aneS(4), 1,4,8,11-tetrathiacyclotetradecane; or [15]aneS(5), 1,4,7,10,13-pentathiacyclopentadecane), formed by treatment of fac-[Mn(CO)(3)(Me2CO)(3)](+) with L in MeCN solution, were readily decarbonylated with Me3NO to yield the first dicarbonyl manganese(I) thioether complexes, cis-[Mn(CO)(2)(L)](+). The crystal structures of [Mn(CO)(3)([12]aneS(4))]CF3SO3 and [Mn(CO)(3)([15]aneS(5))]CF3SO3 confirm the fac tricarbonyl arrangement, with the macrocycle bonded in a tridentate manner, leaving one or two non-bonding S atoms respectively. The crystal structure of cis-[Mn(CO)(2)([12]aneS(4))]CF3SO3. 0.5CHCl(3) reveals a distorted octahedral geometry at Mn-I with the two CO ligands mutually cis and with the tetradentate macrocycle occupying the other four co-ordination sites. IR spectroscopic studies reveal that the CO stretching vibrations occur at very low frequency, indicating very significant pi-back bonding to the CO ligands, with the thioether ligands behaving essentially as pure sigma donors to the low-valent manganese(I) ion in these systems. [References: 14]