The polyselenidoarsenates [Fe(phen)(3)][As2Se6] (1), [Zn-(phen)(dien)][As2Se6]center dot 2phen (2), [{Mn(phen)(2)}(2)(mu-eta(2),eta(2)-AsSe4)](2)-[As2Se6]center dot H2O (3), and [Ni(phen)(3)][As2Se2(mu-Se-3)(mu-Se-5)] (4) (dien = diethylenetriamine and phen = 1,10-phenanthroline) were prepared by the reaction of As2O3, Se, dien, and phen in the presence of transition metals in a methanol solvent under solvothermal conditions. Compounds 1-3 consist of [As2Se6](2-) anions with [Fe(phen)(3)](2+), [Zn(phen)(dien)](2+), and [{Mn-(phen)(2)}(2)(mu-eta(2),eta(2)center dot AsSe4)](+) complex counter cations, respectively. The [As2Se6](2-) anion is formed from two (AsSe3)-Se-III trigonal pyramids linked through two Se Se bonds. Compound 3 is the first example of a mixed-valent selenidoarsenate(III,V) and exhibits the coexistence of (AsSe3)-Se-III trigonal pyramidal and (AsSe4)-Se-V tetrahedral units. Compound 4 is composed of a helical chain of [As2Se2(mu-Se-3)(mu-Se-5)(2-)](infinity) and octahedral [Ni(phen)(3)](2+) cations. The [As2Se2(mu-Se-3)(mu-Se-5)(2-)](infinity) chain is constructed from AsSe+ units alternatively linked by mu-Se-3(2-) and mu-Se-5(2-) bridging ligands. When the structures of compounds 1-4 are compared, the transition metal ions show different structural directing effects during the synthesis of arsenic polyselenides in methanol. Compounds 1, 2, 3, and 4 exhibit semiconducting properties with band gaps of 1.88, 2.29, 1.82, and 2.01 eV, respectively.