OXIDATIVE DECARBONYLATION OF DIMANGANESE DECACARBONYL BY POLYSELENIDE ANIONS - MOLECULAR-STRUCTURE OF [(C6H5)4P]2[MN2(SE2)2(CO)6].C4H10O, [(C6H5)4P]2[MN2(SE4)2(CO)6], AND [(C6H5)4P]2[MN(SE4)2]

A series of three manganese polyselenide anions has been isolated and characterized. They are all derived from the reaction of Mn2(CO)10 and polyselenide anions in DMF solution. The reaction of Mn2(CO)10 with 1 equiv of K2Se3 in DMF generates [Mn2(Se2)2(CO)6]2- (Ia). Reaction of Mn2(CO)10 with 2 equiv of K2Se3 produces [Mn2(Se4)2(CO)6]2- (IIa), which can also be obtained by reaction of Ia with red selenium. Thermolysis of Iia in DMF leads to [Mn(Se4)2]2- (IIIa), which is the final product of oxidative decarbonylation. Thermolysis of Ia does not appear to lead to IIIa, suggesting that IIa is a necessary intermediate in the oxidative decarbonylation reaction. All three products have been structurally characterized as their [(C6H5)4P]+ salts (I-III). Structural data are as follows. For I: formula = [(C6H5)4P]2[Mn2(Se2)2(CO)6]·C4Hl0O, space group [formula omited], Z = 1, a = 11.120 (6) Å, = 11.319(5) Å, c= 13.062 (7) Å, α = 114.90 (4)°, β = 107.64 (4)°, γ = 90.57 (4)°, V = 1403 (1) Å3, R(Fo) = 0.0688, = 0.0684. For II: formula = [(C6H5)4P]2[Mn2(Se4)2(CO)6], space group P21/n, Z = 2, a = 12.022 (5) Å, b = 14.542 (7) Å, c = 16.251 (8) Å, β = 98.46 (4)°, V = 2810 (1) Å3, R(Fo) = 0.0554, Rw(Fo) = 0.0580. For III: formula = [C6H5)4P]2[Mn(Se4)2], space group P21, Z = 4, a = 10.048 (3) Å, b = 13.394 (4) Å, c = 33.969 (1 1) Å, β = 92.11 (2)°, V = 4756 (1) Å3, R(Fo) = 0.0624, RwFo) = 0.0613. Both carbonyl containing anions, la and Iia, consist of two manganese tricarbonyl fragments chelated by a Sen2- chain (n = 2, 4). One of the terminal selenium atoms on each manganese also bridges to the second metal center, completing its 18-electron count. Thus each metal center is pseudooctahedrally coordinated by three Se atoms and three carbonyl ligands. The monomer IIIa has two Se42- chains chelating to a manganese(II) center in a tetrahedral fashion. © 1990, American Chemical Society. All rights reserved.