Dithioether complexes of manganese carbonyl halides: synthesis, Mn-55 NMR spectroscopic, X-ray crystallographic and electrochemical studies

Reaction of [Mn(CO)(5)X] (X = Cl, Br or I) with RS(CH2)(n)SR (R = Me or Ph, n = 2; R = Me, n = 3) or C6H4(SMe)(2)-o yielded the neutral manganese(I) complexes [MnX(CO)(3) {RS(CH2)(n)SR}] or [MnX(CO)(3){C6H4(SMe)(2)-o}] as yellow or orange solids. These compounds have been characterised using IR,H-1 and C-13-{H-1} NMR spectroscopy, FAB mass spectrometry and microanalyses. X-Ray crystallographic analyses on two examples confirmed a fac-tricarbonyl arrangement, with the dithioether ligand chelating. The complex [MnCl(CO)(3)(MeSCH2CH2SMe)] adopts the DL arrangement, while [MnBr(CO)(3)(PhSCH2CH2SPh)] is in the meso-2 form in the solid state. Manganese-55 NMR spectroscopic studies show that delta(Mn-55) lies in the range +67 to -567 for these compounds, and shifts to low frequency according to the series X = Cl-->Br-->I. For the compounds involving PhSCH2CH2SPh or MeSCH2CH2CH2SMe pyramidal inversion is rapid on the NMR timescale at 300 K, giving a single broad Mn-55 NMR peak. The Mn-55 NMR spectra of the compounds involving MeSCH2CH2SMe and C6H4(SMe)(2)-o show three distinct resonances indicative of the three NMR distinguishable invertomers, meso-1, meso-2 and DL, the population of the meso-1 form decreasing with increasing halogen size. Reaction of [MnBr(CO)(5)] with 1 molar equivalent of MeSCH2SMe yielded the heterobridged dinuclear complex [Mn-2(CO)(6)(mu-Br)(2)(mu-MeSCH2SMe)]. The crystal structure revealed a pseudo-A-frame complex in which the two manganese(I) octahedra edge-share via two bromides with the dithioether bridging the Mn2Br2 core, giving Mn ... Mn 3.71 Angstrom.