SYNTHESIS, STRUCTURE, AND BONDING OF BUTTERFLY CLUSTERS CONTAINING MU(4)-OXO AND MU(4)-SULFIDO LIGANDS - [(PPH(3))(2)N][FE(3)M(CO)(12)(MU(4)-E)] (E=O, S, M=MN, RE)

Metal butterfly clusters that contain quadruply bridging oxo and sulfi de ligands, [PPN][Fe(?)3M(CO)(12)(mu(4)-E)] (PPN = (PPh(3)N+, E = O, S ; M = Mn, Re), were synthesized by condensation reactions between [PPN ](2)[Fe-3(CO)(9)-(mu(3)-E)] (E = O, S) and the electrophilic reagents [Mn(CO)(3)(NCCH3)(3)][PF6] and Re(CO)(5)(OSO2CF3). The structures of [ PPN][Fe3Mn(CO)(12)(mu(4)-O)] ([PPN]2) and [PPN][Fe3Mn(CO)(12)(mu(4)-S) ] ([PPN]5) were determined by single-crystal X-lay diffraction. The di hedral angle between the two wings of the butterfly is 113 degrees for 2 and 130 degrees for 5; presumably, this structural feature arises f rom the larger size of sulfur versus oxygen. The structure of 2 clearl y indicates that the manganese atom occupies a wingtip site in the but terfly array of metal atoms. All of the butterfly clusters were charac terized by variable-temperature C-13 NMR spectroscopy and are assigned structures in which the heterometal occupies a wingtip site. Fenske-H all molecular orbital calculations were performed on 2 and 5 as well a s the parent trinuclear clusters. The electronic structures of [Fe-4(C O)(12)(mu(4)-C)](2-) and [Fe-4(CO)(12)-(mu 4-N)](-), as indicated by F enske-Hall calculations, are compared to those of 2 and 5 to assess th e structural and electronic contributions of oxygen and sulfur to bond ing within the butterfly framework. Crystal data for [PPN]2: monoclini c(P2(1)/c), a = 17.100(2) Angstrom, b = 15.890(1) Angstrom, c = 17.417 (2) Angstrom, beta = 94.90(1)degrees, Z = 4, R (R(w)) 0.037 (0.044). C rystal data for [PPN]5: triclinic (P (1) over bar), a = 11.314(1) Angs trom, b = 18.214(2) Angstrom, c = 11.309(1) Angstrom, alpha a = 90.46( 1)degrees; beta = 90.22(1)degrees, gamma = 89.43(1)degrees, Z = 2, R ( R(w)) = 0.037 (0.056).