| 摘 要： | Reactions of potassium molybdate with racemic malic acid (H3mal = C4H6O5) result in the isolation of two mesomeric molybdenum malate complexes Ks(MoO2)2O(R-mal)2](MoO2)2O(S- mal)2]·4H2O 1 and (Him)2K6(MoO2)4O3(R-mal)2](MoO2)4O3(S-mal)2]·8H2O 2. Complex 1 belongs to the monoclinic system, space group C2/c with a = 14.8637(3), b = 6.9544(1), c = 19.6783(5) A, β = 100.081(2)°, V= 2002.70(7)A3, Mr = 1452.88, Z= 2, F(000) = 1416, T= 173 K, Dc = 2.409 g/cm3, μ(MoKa) = 2.167, R = 0.0283 and wR = 0.0733.2 is of triclinic system, space group P1 with a = 8.7707(2), b = 9.3310(3), c = 17.9093(7) A, α = 83.781(3), β = 85.626(2), γ= 84.822(2)°, V = 1447.84(8) A3, Mr = 2160.68, Z = 1, F(000) = 1048, T= 173 K, Dc = 2.478 g/cm3, μ(MoKα) = 2.230, R = 0.0234 and wR = 0.0584.1 is the first isolated dinuclear molybdenum(Ⅵ) malato complex in 1:1 molar ratio. The molybdenum atoms in the two complexes are six-coordinated in an approximately octahedral geometry. Two malates coordinate tridentately with the Mo atom via their α-alkoxy, α-carboxy and α-carboxy groups in 1 and 2. β-Carboxy group in 2 further links with the other two Mo atoms to give a tetrameric unit. The solution 1H and 13C NMR spectra indicate that dimeric malate molybdenum in 1 dissociates partly in solution and exists in an equilibrium with tetrameric species, while 2 is stable and retains its tetrameric structure without any dissociation.
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