87860-07-9Relevant academic research and scientific papers
Synthesis and stereochemistry of mono-, bi-, and tetranuclear manganese thiolates
Costa, Thomas,Dorfman, Jay R.,Hagen, Karl S.,Holm
, p. 4091 - 4099 (2008/10/08)
The first systematic investigation of Mn-thiolate complexes is described. Anaerobic reaction of MnCl2 with 2.5 equiv of NaSPh in methanol affords [Mn4(SPh)10]2-. The compound (Me4N)2[Mn4(SPh)10] crystallizes in triclinic space group P1 with a = 13.184 (3) ?, b = 23.743 (4) ?, c = 12.930 (3) ?, α = 91.63 (2)°, β = 113.76 (1)°, γ = 79.53 (2)°, and Z = 2 The structure was refined to R (Rw) = 4.5% (4.8%) with use of 5787 unique data (I > 3σ(I)). The anion contains an adamantane-like Mn4(μ-S)6 cage composed of a nearly regular Mn4 tetrahedron and an irregularly distorted S6 octahedron and exhibits terminal and bridging Mn-S mean distances of 2.376 (7) and 2.46 (2) ?, respectively. Selected structura features are compared with those of five other M4(μ-S)6 cages. Anaerobic reaction of MnCl2 with 2 equiv of Na2(1,2-S2C2H4) in methanol forms extremely oxygen-sensitive [Mn(S2C2H4)2]2-. The compound (Me4N)2[Mn(S2C2H 4)2]·MeCN crystallizes in monoclinic space group P21/n with a = 9.833 (5) ?, b = 17.325 (7) ?, c = 13.819 (6) ?, β = 93.43 (2)°, and Z = 4 The structure was refined to R (Rw) = 4.4% (4.5%) with use of 1893 unique data (I > 3σ(I)). The anion is tetrahedral with mean dimensions Mn-S = 2.432 (7) ?, chelate ring ∠S-Mn-S = 91.5°, and a 92.3° dihedral angle between MnS2 planes Exposure of a solution of [Mn(S2C2H4)2]2- to air results in the immediate formation of a dark green color and thereafter isolation of salts of [Mn2(S2C2H4)4] 2-. (Et4N)2[Mn2(S2C2H 4)4] crystallizes in monoclinic space group P21/n with a = 12.039 (4) ?, b = 10.699 (2) ?, c = 15.012 (3) ?, β = 110.89 (2)°, and Z = 2. The structure was refined to R (Rw) =44% (4 9%) with use of 2175 unique data (I > 3σ(I)). The centrosymmetric anion exhibits the lateral dimer structure in which bis chelate monomers are joined by two Mn-S bonds of length 2.632 (2) ?. The two Mn-S5 coordination units approach a trigonal-bipyramidal arrangement and are separated by a Mn-Mn distance of 3.596 (3) ?. [Mn2(S2C2H4)4] 2- is the first characterized Mn(III) thiolate. A compilation of the limited set of all known Mn-S bond distances is provided. [Mn(S2C2H4)2]2- and [Mn4(SPh)10]2- contain tetrahedral Mn(II) sites; [Mn(S2C2H4)2]2- remains tetrahedral and high spin in acetonitrile and DMF solutions. Magnetic and spectral properties of solutions prepared from [Mn2(S2C2H4)4] 2- indicate that the dimer partially (acetonitrile) or completely (Me2SO, DMF) dissociates in solution to form monomeric [Mn(S2C2H4)2(solv)2] 2-. Cyclic voltammetry of these species are in accord with an EiCi mechanism, in which the initial reduction product, [Mn(S2C2H4)2(solv)2]2-, rapidly and irreversibly converts to [Mn(S2C2H4)2]2-. This species is irreversibly oxidized to [Mn(S2C2H4)2(solv)2] - at less cathodic potentials. The large ΔEp values (0.52 V (acetonitrile), 0.76 V (DMF)) are consistent with different electroactive orbitals of [Mn(S2C2H4)2]2- and [Mn(S2C2H4)2(solv)2] - required by tetrahedral and six-coordinate structures, respectively. Spectral evidence is presented for Mn(III) species of the type [Mn(S2C2H4)2(py)2] - as the green chromophores formed in an aerobic colorimetric test for vicinal dithiols developed some years earlier.
