Heavier Chalcogenate-Bridged Manganese Carbonyl Complexes: Synthesis, Reactivity, and Electrochemical Investigation

The chemistry and electrochemical properties of heavier chalcogen-supported (Se or Te) dimanganese complexes have been described. The photolytic reaction of [Mn₂(CO)₁₀] with NaER [E = S, R = Ph; E = Se, R = Ph; E = Te, R = Ph; E = Se, R = ─C₆H₄-p-NMe₂], followed by [(n-Bu)₄NI] led to the formation of [(n-Bu)₄N]⁺[(CO)₃Mn(μ-ER)₃Mn (CO)₃]¯ [E = S, R = Ph (1); E = Se, R = Ph (2); E = Te, R = Ph (3); E = Se, R = ─C₆H₄-p-NMe₂ (4)] complexes. Complexes 1 and 2 were employed for electrocatalytic hydrogen evolution in the presence of HBF₄. The reported complexes were found to be catalytically inefficient. Complexes 1-4 showed quasi-reversible oxidation peaks, and the reaction of 2 and 3 with dry oxygen resulted in the formation of dichalcogenides. This illustrates, in particular, how these complexes' oxygen tolerance differs owing to the chalcogen identity. The reaction of these trichalcogenate-bridged dimanganese complexes 2 and 4 with HBF₄, resulted in the formation of cubane-type structure [(CO)₃Mn(μ-SeR)]₄ [E = Se, R = Ph (VII); E = Se, R = ─C₆H₄-p-NMe₂ (5)]. The photolytic reaction of [Mn₂(CO)₁₀] with NaER [E = Se, R = ─C₆H₄-p-NMe₂], followed by (Cp*CoCl)₂ resulted in the formation of a heterobimetallic triselenolate-bridged complex (6). These complexes were characterized by employing different multinuclear NMR, IR spectroscopies, single-crystal X-ray diffraction analyses, and mass spectrometry.