Synthesis and structure of trinuclear clusters (Et(4)N)(2)[(mu(3)-Se)Fe-3(CO)(9)], [(mu-H)(2)Fe-3(mu(3)-Se)(CO)(9)], and [(mu(3)-Se)FeMo2(eta(5)-C5H5)(2)(Co)(7)]

The cluster anion [Fe-3(mu(3)-Se)(CO)(9)](2-) (I) was isolated as a salt (Et(4)N)(2)(I) by the reaction of Fe(CO)(5) with Na2Se in isopropanol. The protonated form, (mu-H)(2)Fe-3(mu(3)-Se)(CO)(9) (II), was obtained by acidifying the reaction mixture and used for the synthesis of the heterometallic cluster FeMo2(mu-Se)(CO)(7)Cp(2) (III), Cp=eta(5)-C5H5. The structure of I and III was established by X-ray diffraction analysis. Crystals I are monoclinic, a=14.210(3), b=11.547(3), c=19.831(2) Angstrom, beta=90.92(2)degrees, V-cell=3254(1) Angstrom(3), space group P2/c, Z=4, d(calc)=1.550 g/cm(3), Syntex p2(1), lambda CuKalpha, R(F)=0.1333 for 1264 F-hld>6 sigma(F-hkl). Crystals III are monoclinic, a=20.440(5), b=12.771(3), c=16.342(4) Angstrom, beta=113.80(2)degrees, V-cell=3903(2) Angstrom(3), space group P2(1)/c, Z=8, d(calc)=2.222 g/cm(3), Syntex P2(1), lambda CuKalpha, R(F)=0.0734 for 116 F-hld>4 sigma(F-hkl). The structure of II was inferred from the Mossbauer, IR, and H-1 and Se-77 NMR spectroscopy data.