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The anionic syn-/anti-[Fe(μ-SEt)(NO)2]2- (2a) were synthesized and characterized by IR, UV-vis, EPR, and X-ray diffraction. The geometry of the [Fe(μ-S)2Fe] core is rearranged in going from [{Fe(NO)2}9-{Fe(NO)2}9J Roussin's red ester [Fe(μ-SEt)(NO)2]2 (la) (Feߪ Fe distance of 2.7080(5) Å) to the [{Fe(NO)2}9-{Fe(NO)2}10] complex 2a (Fe ߪ Fe distance of 2.8413(6) Å) to minimize the degree of Fe ߪ Fe interaction to stabilize complex 2a. On the basis of X-ray absorption (Fe K- and L-edge), EPR and SQUID, complex 2a is best described as the anionic [{Fe(NO)2}9-{Fe(NO)2}10] Roussin's red ester with the fully delocalized mixed-valence core. The complete bridged- thiolate cleavage yielded DNIC [(EtS)2Fe(NO)2]- (3a) in the reaction of 2 equiv of [EtS]- and complex 1a, whereas reaction of 2 equiv of [tBuS]- with [Fe(μ-StBu)(NO)2]2 (1b) gave DNIC [(tBuS)2Fe(NO)2]- (3b) and the anionic Roussin's red ester [Fe(μ-StBu)(NO)2]2- (2b) through bridged-thiolate cleavage in combination with reduction. In contrast to the inertness of DNIC 3b toward complex 1b, nucleophile DNIC 3a induces the reduction of complex la to produce the anionic Roussin's red ester 2a. Interestingly, dissolution of complex 3a in MeOH at 298 K finally led to the formation of a mixture of complexes 2a and 3a, in contrast to the dynamic equilibrium of complexes 3b and lb observed in dissolution of complex 3b in MeOH. These results illustrate the aspect of how the steric structures of nucleophiles ([EtS]- vs [tBuS]- and [(EtS)2Fe(NO)2]- vs [(tBuS)2Fe(NO)2]-) function to determine the reaction products. [ABSTRACT FROM AUTHOR]

Two new isostructural complexes [M(H2biim)3][M(btc)(Hbiim)]•2H2O (M = Co, (1); M = Ni, (2)) (btc = 1,3,5-benzenetricarboxylate; H2biim = 2,2′-biimidazole) have been synthesized and characterized by single-crystal X-ray diffraction. They present a unique structure consisting of two distinct units: the monomeric cations [M(H2biim)3]2+ and the two-dimensional (2D) anionic polymer [M(Hbiim)(btc)]2-. In the anionic moiety, the Hbiim monoanion is simultaneously coordinated to one metal atom in a bidentate mode and further to another metal atom in a monodentate mode. The imidazolate groups bridge the two adjacent metal ions into a helical chain which is further arranged in left- and right-handed manners. These chains are bridged by btc ligands into a 2D brick wall structure. The most interesting aspect is that the [M(H2biim)3]2+ cations act as pillars and link the anionic layers via robust heteromeric hydrogen-bonded synthons R²2(9) and R¹2(7) formed by the uncoordinated oxygen atoms of carboxylate groups and the H2biim ligands, resulting in a microporous metal-organic framework with one-dimensional (1D) channels (ca. 11.85 Å ⊗ 11.85 Å for 1 and 11.43 Å ⊗ 11.43 Å for 2). Magnetic properties of these two complexes have also been studied in the temperature range of 2–300 K, and their magnetic susceptibilities obey the Curie-Weiss law in the temperature range of 20–300 K (for 1) and 2–300 K (for 2), respectively, showing anti-ferromagnetic coupling through imidazolate bridging. Taking into consideration the Heisenberg infinite chain model as well as the possibility of chain-to-chain and chain-to-cation interactions, the anti-ferromagnetic exchange of 2 is analyzed via a correction for the molecular field, giving the values of gcat = 2.296, gNi = 2.564, J = -13.30 cm-1, and zJ′ = -0.017 cm-1. The microporous frameworks are stable at ca. 350 °C. They do not collapse after removal of the guest water molecules in the channels, and they adsorb methanol molecules selectively. [ABSTRACT FROM AUTHOR]