SUBSTITUTION AND REDOX CHEMISTRY OF [BU4N](2)[TA6CL12(OSO2CF3)(6)]

Two sequential electrochemical reductions occur for the cluster anion [Ta6Cl12(OSO2CF3)(6)](2-) at 0.89 and 0.29 V vs Ag/AgCl, with the gene ration [Ta6Cl12(OSO2CF3)(6)](3-) and [Ta6Cl12(OSO2CF3)(6)](4-). Chemic al reduction of [Ta6Cl12(OSO2CF3)(6)](2-) by ferrocene produces [Ta6Cl 12(OSO2CF3)(6)](3-) With the concomitant shift of the v(SO2) stretch f rom 1002 to 1018 cm(-1). Reaction of [Bu4N](2)[Ta6Cl12(OSO2CF3)(6)] (1 ) With [Bu4N]X (X = Cl, Br, I, NCS) occurs by reduction and substituti on, yielding [Bu4N](3)[Ta6Cl12X6], where the clusters with X = Br, I, and NCS are new. Spectroscopic (IR and UV-vis) evidence indicates that the reduced cluster core {Ta6Cl12}(2+) is produced in reaction mixtur es of 1 with the halide and pseudohalide ions. Concomitant substitutio n of the triflate ligands of 1 by X- occurs nd the rates for the overa ll reduction and substitution increase in the order X- = Cl- < Br- < N CS- < I- < CN-. Reduction of 1 with ferrocene followed by addition of [Bu4N]O2CCH3 produces the new cluster [Ta6Cl12(O2CCH3)(6)](3-) isolate d as the tetrabutylammonium salt. Cyclic voltammetry and UV-vis spectr oscopy on the new clusters [Bu4N](3)[Ta6Cl12X6] (X = Br, I, NCS, and O 2CCH3) are reported. Crystal data for [Bu4N](3)[Ta6Cl12(NCS)(6)]. CH2C l2: monoclinic, space group, P2(1)/c(No. 14); a = 25.855(6) Angstrom, b = 21.843(6) Angstrom, c = 16.423(3) Angstrom; beta = 100.03(2)degree s; V = 9133(3)Angstrom(3); Z = 4.