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New heterobimetallic tetranuclear complexes of formula [Fe(III){B(pz)(4)}(CN)(2)(μ-CN)Mn(II)(bpy)(2)](2)(ClO(4))(2)·CH(3)CN (1), [Fe(III){HB(pz)(3)}(CN)(2)(μ-CN)Ni(II)(dmphen)(2)](2)(ClO(4))(2)·2CH(3)OH (2a), [Fe(III){B(pz)(4)}(CN)(2)(μ-CN)Ni(II)(dmphen)(2)](2)(ClO(4))(2)·2CH(3)OH (2b), [Fe(III){HB(pz)(3)}(CN)(2)(μ-CN)Co(II)(dmphen)(2)](2)(ClO(4))(2)·2CH(3)OH (3a), and [Fe(III){B(pz)(4)}(CN)(2)(μ-CN)Co(II)(dmphen)(2)](2)(ClO(4))(2)·2CH(3)OH (3b), [HB(pz)(3)(-) = hydrotris(1-pyrazolyl)borate, B(Pz)(4)(-) = tetrakis(1-pyrazolyl)borate, dmphen = 2,9-dimethyl-1,10-phenanthroline, bpy = 2,2'-bipyridine] have been synthesized and structurally and magnetically characterized. Complexes 1-3b have been prepared by following a rational route based on the self-assembly of the tricyanometalate precursor fac-[Fe(III)(L)(CN)(3)](-) (L = tridentate anionic ligand) and cationic preformed complexes [M(II)(L')(2)(H(2)O)(2)](2+) (L' = bidentate α-diimine type ligand), this last species having four blocked coordination sites and two labile ones located in cis positions. The structures of 1-3b consist of cationic tetranuclear Fe(III)(2)M(II)(2) square complexes [M = Mn (1), Ni (2a and 2b), Co (3a and 3b)] where corners are defined by the metal ions and the edges by the Fe-CN-M units. The charge is balanced by free perchlorate anions. The [Fe(L)(CN)(3)](-) complex in 1-3b acts as a ligand through two cyanide groups toward two divalent metal complexes. The magnetic properties of 1-3b have been investigated in the temperature range 2-300 K. A moderately strong antiferromagnetic interaction between the low-spin Fe(III) (S = 1/2) and high-spin Mn(II) (S = 5/2) ions has been found for 1 leading to an S = 4 ground state (J(1) = -6.2 and J(2) = -2.7 cm(-1)), whereas a moderately strong ferromagnetic interaction between the low-spin Fe(III) (S = 1/2) and high-spin Ni(II) (S = 1) and Co(II) (S = 3/2) ions has been found for complexes 2a-3b with S = 3 (2a and 2b) and S = 4 (3a and 3b) ground spin states [J(1) = +21.4 cm(-1) and J(2) = +19.4 cm(-1) (2a); J(1) = +17.0 cm(-1) and J(2) = +12.5 cm(-1) (2b); J(1) = +5.4 cm(-1) and J(2) = +11.1 cm(-1) (3a); J(1) = +8.1 cm(-1) and J(2) = +11.0 cm(-1) (3b)] [the exchange Hamiltonian being of the type Ĥ = -J(Ŝ(i)·Ŝ(j))]. Density functional theory (DFT) calculations have been used to substantiate the nature and magnitude of the exchange magnetic coupling observed in 1-3b and also to analyze the dependence of the exchange magnetic coupling on the structural parameters of the Fe-C-N-M skeleton.

The present study refers to a variety of reduced metal-oxide core-shell hybrids, which are unique with regard to their electronic structure, their geometry, and their formation. They contain spherical {Mo(72)Fe(30)} Keplerate-type shells encapsulating Keggin-type polyoxomolybdates based on very weak interactions. Studies on the encapsulation of molybdosilicate as well as on the earlier reported molybdophosphate, coupled with the use of several physical methods for the characterization led to unprecedented results (see title). Upon standing in air at room temperature, acidified aqueous solutions obtained by dissolving sodium molybdate, iron(II) chloride, acetic acid, and molybdosilicic acid led to the precipitation of monoclinic greenish crystals (1). A rhombohedral variant (2) has also been observed. Upon drying at room temperature, compound 3 with a layer structure was obtained from 1 in a solid-state reaction based on cross-linking of the shells. The compounds 1, 2, and 3 have been characterized by a combination of methods including single-crystal X-ray crystallography, magnetic studies, as well as IR, Mossbauer, (resonance) Raman, and electronic absorption spectroscopy. In connection with detailed studies of the guest-free two-electron-reduced {Mo(72)Fe(30)}-type Keplerate (4) and of the previously reported molybdophosphate-based hybrids (including (31)P NMR spectroscopy results), it is unambiguously proved that 1, 2, and 3 contain non-reduced Keggin ion cores and reduced {Mo(72)Fe(30)}-type shells. The results are discussed in terms of redox considerations (the shell as well as the core can be reduced) including those related to the reduction of "molybdates" by Fe(II) being of interdisciplinary including catalytic interest (the Mo(VI)/Mo(V) and Fe(III)/Fe(II) couples have very close redox potentials!), while also referring to the special formation of the hybrids based on chemical Darwinism.

The synthesis, structure and magnetic properties of the first thiooxoverdazyl metal complex (Cu(hfac) 2 (Svdpy)] [hfac = (1,1,1,5,5,5)-hexafluoroacetylacetonate; Svdpy = 1,5-dimethyl-3-(2-pyridyl)-6-thiooxoverdazyl] is described. The organic radical acts as a bidentate ligand leading to a six-coordinate metal complex. The fit of the thermal variations of the magnetic susceptibility reveal a ferromagnetic intramolecular exchange interaction. This finding is confirmed and analysed by using wavefunction-based methods which indicate that the exchange interaction is governed by the substituent of the radical rather than by its heteroatom.

[(η6-Pentamethylbenzene)Mn(CO)3]+BF4− 1 and [(η6-1,2,4,5-tetramethylbenzene)Mn(CO)3]+BF4− 2 complexes were prepared and reacted with nucleophiles to provide neutral exo-substituted (η5-polymethylcyclohexadienyl)Mn(CO)3 complexes 3−6. To study the regioselectivity of the deprotonation at a “benzylic” position of (η5-methylcyclohexadienyl)Mn(CO)3 complexes, compounds 3−6 were submitted to a lithiation/electrophilic quench sequence, and functionalized complexes 9−18 were obtained in good yields and with a total regioselectivity. A second sequence gave rise to the formation of unprecedented bifunctionalized (η5-1,2,4,5-tetramethylcyclohexadienyl)Mn(CO)3 and (η5-pentamethylcyclohexadienyl)Mn(CO)3 complexes 19−22.

The coordination properties of vacant bisphosphonate derivatives of polyoxometalates, with easily tunable functions, have been explored. The preparation and crystallographic structure of their La(3+) and Zr(4+) complexes are described herein.

A new 1D coordination polymer comprised of [MnIII6O2(Et-sao)6(EtOH)4(H2O)2]2+ units and bithiophene dicarboxylato was synthesized by mixing EtsaoH2 (salicylaldoxime), H2btda (2,2′-bithiophene-5,5′-dicarboxylic acid) and Mn(ClO4)2·6H2O in the presence of NEt4OH. The crystal structure was determined and consists of Mn6 clusters bridged by the bithiophene dicarboxylato ligands coordinated to two of the MnIII ions of the Mn6 polynuclear complex. Direct current magnetic measurements show an overall ferromagnetic interaction between the MnIII ions within the Mn6 cluster leading to an S = 12 ground state for the Mn6 unit. Furthermore, this compound presents single-molecule magnet behaviour. Slow relaxation of the magnetization is observed at low temperature following a thermal activated regime with Ueff≈ 50 K and τ0≈ 2.2 10−10 s. The magnetic measurements do not show any noticeable interaction between the Mn6 clusters through the bithiophene dicarboxylato bridges.