Stepwise construction of manganese-chromium carbonyl chalcogenide complexes: synthesis, electrochemical properties, and computational studies.

When trigonal-bipyramidal clusters, [PPN][E2Mn3(CO)9] (E = S, Se), were treated with Cr(CO)6 and PPNCl in a molar ratio of 1:1:2 or 1:2:2 in 4 M KOH/MeCN/MeOH solutions, mono-Cr(CO)5-incorporated HE2Mn3-complexes [PPN]2[HE2Mn3Cr(CO)14] (E = S, [PPN]2[1a]; Se, [PPN]2[1b]), respectively, were formed. X-ray crystallographic analysis showed that 1a and 1b were isostructural and each displayed an E2Mn3 square-pyramidal core with one of the two basal E atoms externally coordinated with one Cr(CO)5 group and one Mn–Mn bond bridged by one hydrogen atom. However, when the TMBA+ salts for [E2Mn3(CO)9]− were mixed with Cr(CO)6 in a molar ratio of 1:1 in 4 M KOH/MeOH solutions and refluxed at 60 °C, mono-Cr(CO)3-incorporated E2Mn3Cr octahedral clusters [TMBA]3[E2Mn3Cr(CO)12] (E = S, [TMBA]3[2a]; Se, [TMBA]3[2b]), respectively, were obtained. Clusters 2a and 2b were isostructural, and each consisted of an octahedral E2Mn3Cr core, in which each Mn–Mn or Mn–Cr bond of the Mn3Cr plane was semibridged by one carbonyl liga...