SYNTHESIS AND CHARACTERIZATION OF 4 CONSECUTIVE MEMBERS OF THE 5-MEMBER [FE6S8(PET(3))(6)](N-4) CLUSTER ELECTRON-TRANSFER SERIES() (N=0)

The clusters [Fe6S8(PEt(3))(6)](+,2+) have been shown by other investi gators to be formed by the reaction of [Fe(OH2)(6)](2+) and H2S, to co ntain face-capped octahedral Fe6S8 cores, and to be components of the five-membered electron transfer series [Fe6S8(PEt(3))(6)](n+) (n = 0-4 ) established electrochemically. We have prepared two additional serie s members. Reaction of [Fe6S8(PEt(3))(6)](2+) with iodine in dichlorom ethane affords [Fe6S8(PEt(3))(6)](3+), isolated as the perchlorate sal t (48%). Reduction of [Fe6S8(PEt(3))(6)](2+) With Na(Ph(2)CO) in aceto nitrile/THF produces the neutral cluster [Fe6S8(PEt(3))(6)] (65%). The structures of the four clusters with n = 0, If, 2+, 3+ were determine d at 223 K. The compounds [Fe6S8(PEt(3))(6)](ClO4)(3), [Fe6S8(PEt(3))( 6)] crystallize in trigonal space group R(3) over barc$ with a = 21.69 1(4), 16.951(4) Angstrom, c = 23.235(6), 19.369(4) Angstrom, and Z = 6 , 3. The compounds [Fe6S8(PEt(3))(6)](BF4)(2), [Fe6S8(PEt(3))(6)](BF4) . 2MeCN were obtained in monoclinic space groups P2(1)/c, C2/c with a = 11.673(3), 16.371(4) Angstrom, b = 20.810(5), 16.796(4) Angstrom, c = 12.438(4), 23.617(7) Angstrom, beta = 96.10(2), 97.98(2)degrees, and Z = 2, 4. [Fe6S8(PEt(3))(6)](BPh(4))(2) occurred in trigonal space gr oup P (1) over bar with a = 11.792(4) Angstrom, b = 14.350(5) Angstrom , c = 15.536(6) Angstrom, alpha = 115.33(3)degrees, beta = 90.34(3)deg rees, gamma = 104.49(3)degrees, and Z = 1. Changes in metric features across the series are slight but indicate increasing population of ant ibonding Fe6S8 core orbitals upon reduction. Zero-field Mossbauer spec tra are consistent with this result, isomer shifts increasing by ca. 0 .05 mm/s for each electron added, and indicate a delocalized electroni c structure. Magnetic susceptibility measurements together with previo usly reported results established the ground states S = 3/2 (3+), 3 (2 +), 7/2 (1+), 3 (0) The clusters [Fe6S8(PEt(3))(6)](n+) possess the st ructural and electronic features requisite to multisequential electron transfer reactions. This work provides the first example of a cluster type isolated over four consecutive oxidation states. Note is also ma de of the significance of the [Fe6S8(PEt(3))(6)](n+) cluster type in t he development of iron-sulfur-phosphine cluster chemistry.