INDUCED INTERNAL ELECTRON-TRANSFER CHEMISTRY IN RHENIUM SULFIDE SYSTEMS

This paper demonstrates the proclivity with which high-valent rhenium sulfur complexes undergo internal electron transfer. Specifically, rea ction of [Et(4)N][ReS4] with 1.5 molar equiv of tetraalkylthiuram disu lfide in acetonitrile gives the dinuclear Re(TV) complexes, Re-2(mu-S) (2)(S(2)CNR(2))(4), 1, in very high yield. This dimer reacts with an a dditional equivalent of tetraalkylthiuram disulfide in the presence of excess Lewis acids, or with 0.5 molar equiv of tetraalkylthiuram disu lfide and 1 molar equiv of [Cp(2)Fe][PF6], to give the dinuclear Re(II I) species [Re-2(mu-S-S(2)CNR(2))(2)(S(2)CNR(2))(3)](+), 2, in high yi eld. The reaction of [ReS4](-) with 3 molar equiv of tetraalkylthiuram disulfide in a mixture of dichloromethane and acetonitrile gives the mononuclear Re(V) species [Re(S2CN(R)(2))(4)]-[Cl], 3, in high yield. Each of these reactions involves induced internal electron transfer in which the formal oxidation state of the metal center is reduced by th e addition of an oxidant (i.e., tetraalkylthiuram disulfide). The boun d sulfide is the reductant both for the metal and the external oxidant . The reformation of 1 from 2, in which the metal is oxidized, can be effected using reductants such as H-2. Electrochemical properties and chemical reactivities of the complexes are presented. The Re-2(mu-S)(2 )(S(2)CNR(2))(4) dimer undergoes a reversible one-electron oxidation t o produce Re-2(mu-S)(2)(S(2)CNR(2))4(+), 1(+) This species can be gene rated chemically and, in the presence of excess sulfur, forms a novel Re(TV) sulfur-bridged dicationic dimer-of-dimers, [(Re-2(mu-S)(S(2)CNR (2))(4))(2)S-4](2+), 4. The reaction of 1(+) with tetraalkylthiuram di sulfide give 2, which can be reconverted to 1 electrochemically via an EEC reaction. Single crystal X-ray diffraction studies of 1-i-Bu (P2( 1)/c (No. 14), a = 11.084(2) Angstrom, b = 13.815(3) Angstrom, c = 19. 945(4) Angstrom, beta = 92.23(2)degrees, V = 3052(2) Angstrom(3)), [2- Me][O3SCF3] (P ($) over bar 1 (No. 2), a = 14.238(4) Angstrom, b = 11. 476(4) Angstrom, c = 14.977(5) Angstrom, alpha = 112.28(2)degrees beta = 117.70(2)degrees gamma = 89.14(2)degrees, V = 1966(1) Angstrom(3)), [3-Me][Cl] (C2/e (No. 15), a = 13.174(4) Angstrom, b = 18.736(6) = An gstrom, c = 9.826(3) Angstrom, beta = 96.46(2)degrees, V = 2410(1) Ang strom(3)), and [4-i-Bu][PF6](2) (P2(1) (No. 4), a = 15.754(3) Angstrom , b = 22.505(5) Angstrom, c = 20.278(6) Angstrom, beta = 115.12(2)degr ees, V = 6510(3) Angstrom(3)), are described where the symbols after t he number designate the alkyl group, R, of the particular complex.