Tetranuclear Mo2Rh2 complexes obtained from reactions between triple cubane-type oxide cluster [(CP*Rh)(4)Mo4O16] (Cp* = eta(5)-C-5(CH3)(5)) and methanethiol: [{Cp*Rh(mu-SCH3)(3)MoO2}(2)(mu-O)] and [{Cp*Rh(mu-SCH3)(3)MoO}(2)(mu-X)(mu-Y)] (X, Y = O and X = O, Y = S). Synthesis, X-ray structures, anddynamic behavior in nonaqueous media

A new series of linear-type Mo2Rh2 tetranuclear complexes, [{Cp*Rh-III(mu-S CH3)(3)MoVIO2}(2)(mu-O)] (1), [{Cp*Rh-III(mu-SCH3)(3)(MoO)-O-V}(2)(mu-O)(2) ] (2), and [{Cp*Rh-III(mu-SCH3)(3)(MoO)-O-V}(2)(mu-O)(mu-S)] (3), has been prepared from reactions of the triple cubane-type oxide cluster [(Cp*Rh)(4) Mo4O16]. 2H(2)O with CH3SH. These tetranuclear complexes have been characte rized by elemental analysis, infrared, electronic, and H-1, C-13, and O-17 NMR spectroscopies as well as X-ray analysis. Complex 1 crystallizes in the monoclinic space group P2(1)/n (No. 14) with a = 15.348(3), b = 14.059(3), c = 17.879(3) Angstrom, beta = 107.11(2)degre es, V = 3690(1) Angstrom(3), and Z = 4. Complex 2 crystallizes in the monoc linic space group C2/c (No. 15) with a = 25.334(4), b = 21.271(2), c = 17.8 31(3) Angstrom, beta = 129.70(5)degrees, V = 7393(2) Angstrom(3), and Z = 8 . Complex 3 crystallizes in the orthorhombic space group Pcab (No. 61) with a = 16.902(3), b = 26.631(3), c = 16.855(2) Angstrom, V = 7587(3) Angstrom (3), and Z = 8. Complex 1 involves a nearly linear "O2MoVI(mu-O)(MoO2)-O-VI " framework, to which two Cp*Rh-III units are linked by mu-SCH3 ligands. Co mplexes 2 and 3 have an analogous tetranuclear (Mo2Rh2III)-Rh-V structure i n which the Mo-V and Rh-III atoms are bridged by three mu-SCH3 ligands. Com plex 2 contains a doubly-bridged "OMoV(mu-O)(2)(MoO)-O-V" framework with an Mo-Mo distance of 2.564(1) Angstrom, while 3 contains a "OMoV(mu-O)(mu-S)( MoO)-O-V" framework with an Mo-Mo distance of 2.666(1) Angstrom. Complexes 2 and 3 retain the tetranuclear structure but are fluxional in solution. Th e fluxional behaviors are due to intramolecular rotations of the "Cp*Rh(mu- SCH3)" moieties on the trigonal planes of the octahedral Mo centers. Linesh ape analyses of variable-temperature H-1 NMR spectra measured in C6D5Cl yie ld activation parameters of Delta H double dagger = +80.2 kJ mol(-1), Delta S double dagger = +22.1 J K-1 mol(-1), and Delta G(298 K)double dagger = 73.6 kJ mol(-1) for the rotation in 2 and Delta H double dagger = +76.8 kJ mol(-1), Delta S double dagger = +21.1 J K-1 mol(-1), and Delta G(298 K)dou ble dagger = +70.5 kJ mol(-1) for that in 3.