The reaction of SeO2 with Mn2(CO)10/KOH in methanol solution forms a trigonal bipyramid cluster anion [Se2Mn3(CO)9]- (Ia). Cluster la can also be synthesized from the treatment of Se powder with Mn2(CO)10/KOH in 2:1 molar ratio in methanol solution. If Se is reacted with Mn2(CO)10/KOH in a molar ratio of 8:1, the deoxygenation occurs to produce a novel cluster [Se8C2Mn2(CO)6]2- (IIa). Cluster IIa can readily transform into a new octahedral cluster [Se8C2Mn4(CO)12]2- (IIIa) by further treatment with Mn2(CO)10/KOH in CH2C12/ MeOH solutions, and the use of a molar ratio of 1:1 of Se powder to Mn2(CO)10/KOH in methanol also can yield complex IIIa. In the sulfur-manganese system, the synthesis of the analogous complexes [S2Mn3(CO)9]- (Ib), [S8C2Mn2(CO)6]2- (IIb), and [S2Mn4(CO)12]2- (IIIb) also can be accomplished from the reactions of S powder with Mn2(CO)10/KOH in similar fashions. Clusters Ia-IIIa and Ib-IIIb are fully characterized by spectroscopic methods or/and X-ray analyses. The novel clusters [E8C2Mn2(CO)6]2- (E = Se, IIa; E = S, IIb) each consist of two separate Mn(CO)3 groups which are doubly bridged by two CE4 fragments. Clusters Ia and Ib each display a trigonal bipyramid framework with two chalcogen atoms in the axial positions, while clusters IIIa and IIIb each exhibit an octahedral metal skeleton.
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