A new set of covalent atomic radii has been deduced from crystallographic data for most of the elements with atomic numbers up to 96. The proposed radii show a well behaved periodic dependence that allows us to interpolate a few radii for elements for which structural data is lacking, notably the noble gases. The proposed set of radii therefore fills most of the gaps and solves some inconsistencies in currently used covalent radii. The transition metal and lanthanide contractions as well as the differences in covalent atomic radii between low spin and high spin configurations in transition metals are illustrated by the proposed radii set.
A new family of functionalized ligands derived from norborn-5-ene-2,3-dicarboxylic anhydride has been used in Suzuki C-C cross-couplings between aryl boronic acids and aryl bromide derivatives in [BMI][PF(6)] (BMI=1-n-butyl-3-methyl-imidazolium), using palladium acetate as catalytic precursor. High conversions and yields are obtained when amine ligands containing hydroxy groups are involved. TEM analyses after catalysis show the formation of small nanoparticles, in contrast to the agglomerates observed when nanoparticles are intentionally preformed, with a consequent decrease in the catalytic activity in the latter case. Some tests, including the correlation effect between solvent and ligand, are carried out to try to identify the true nature of the catalyst. All the results obtained suggest that formation of nanoparticles is required to lead to a catalytically active system.
Control of the dimensionality and nuclearity in pyraziloximatocopper(II) chemistry has been achieved by tuning of the donor properties of the counteranions.
Assembly of triangular {Mn(III)(3)(O)(salox)(3)}(+) fragments mediated by azido ligands, results in the dodecanuclear [Mn(12)O(4)(salox)(12)(N(3))(4)(MeOH)(4)(H(2)O)(2)] complex with S = 8 ground state and SMM response.
Series of manganese clusters derived from 2-pyridylcyanoxime with Mn3(II) (1), Mn4(II) (2a, b), Mn(II)4Mn(III)4 (3), Mn(II)2Mn(III)6Mn(IV)2 (4) and Mn(II)3Mn(III)6Mn(IV) (5) cores have been characterized. Dc magnetic measurements reveal antiferromagnetic coupling for 1-4 and dominant ferromagnetic interactions for 5 which shows the largest ground state reported to date in pyridyloximate chemistry (S = 14).
Reactions of 2,6-diacetylpyridine dioxime (dapdoH₂) with Mn(NO₃)₂ or Mn(SO₃CF₃)₂ under a variety of conditions or co-ligands yield compounds with the formula [Mn₆O₂(OMe)₂(dapdo)₂(dapdoH)₄](X)₂ in which X = NO₃⁻ (1) or SO₃CF₃⁻ (2), [Mn₈O₂(dapdo)₆(NO₃)₂]·H₂O (3) and [Mn(dapdoH₂)(N₃)₂](n) (4). Compounds 1, 3 and 4 were structurally characterized and equivalent structures for 1 and 2 were inferred from spectroscopic and analytical results. Compounds 1 and 2 consist of hexanuclear Mn₂(II)Mn₄(III) complexes whereas 3 consists of an octanuclear Mn₆(II)Mn₂(III) cluster in which the manganese atoms exhibit a rare bicapped elongated octahedral topology. Compound 4 consists of a 1D system bridged by double end-on azido ligands. Variable temperature magnetic studies were performed between 2-300 K, confirming the ground state S = 5 for 1 and 2, S = 0 for 3 and ferromagnetic response for 4.
The systematic exploration of the reactivity of [Mn(hfacac) 2 ] with R-salicyloximes (R-saloxH 2 : R = H, Me, Et) yielded a family of clusters with nuclearities ranging from Mn 4 to Mn 12 . The compounds with formula [Mn 6 (O) 2 (salox) 6 -(CF 3 COO) 2 (EtOH) 4 ] (1) and [Mn 12 (salox) 12 (O) 4 (N 3 ) 4 (H 2 O) 2 -(MeOH) 6 ] (4) show two or four linked {Mn(μ 3 -O)(salox) 3 } + triangular subunits. Magnetic measurements revealed spin [a]
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