First Example of a Cu^II Polymeric Complex Having a Tetranuclear Repeating Unit with a <i>S</i> = 2 Ground State. Crystal Structure of [Cu₄(dpk·CH₃O)₂Cl₆]<i>_n</i> (dpk·CH₃OH = Unimethylated Diol of Di-2-pyridyl Ketone)

The synthesis, crystal structure and properties of the compound [Cu4(dpk·CH3O)2Cl6]n (dpk·CH3OH = unimethylated diol of di-2-pyridyl ketone) (1), the first example of a copper(II) polymer having a tetrameric repeating unit with S = 2 ground state is reported. The synthesis of compound 1 has been achieved via the reaction of CuCl2 with dpk in methanol. The base-catalyzed addition results in the formation of a unimethylated diol which may deprotonated. Crystal structure data:  [C12H11N2O2Cl3Cu2], Mr = 448.68; triclinic; space group P1̄; a = 7.800(1) (Å); b = 8.946(1) (Å); c = 13.383(1) (Å); α = 118.964(3)°; β = 92.693(3)°; γ = 66.824(3)°; Z = 2. Variable temperature magnetic susceptibility measurements indicate the presence of a ferromagnetic behavior with antiferromagnetic coupling below 15 K. The best fit parameters obtained from this model are J1 = 71.32 cm-1, J2 = 1.43 cm-1, J3 = 0.07 cm-1, J4 = 0 (fixed), zJ = −0.553 cm-1, and g = 2.1 (fixed). The energy levels obtained from the fitting procedure show a S = 2 ground state. The polycrystalline powder EPR spectra at 4.1 K, show an intense broad signal spread over 3900 G with g = 2.34, indicative of a bulk concentration of copper ions having strong ferromagnetic interaction

Methanolysis as a Route to Gallium(III) Clusters: Synthesis and Structural Characterization of a Decanuclear Molecular Wheel

Treatment of a methanolic solution of gallium(III) nitrate with lithium hydroxide in the presence of benzilic acid resulted in the decanuclear cluster [Ga(OMe)2{O2CC(OH)Ph2}]10 (1). The metal and the organic components have assembled to form a cyclic molecule that adopts the structure of a wheel. The 10 GaIII ions are approximately coplanar and are coordinated in a distorted octahedral manner by six oxygen atoms. The integrity of the molecular wheel is retained in solution, as evidenced by the 1NMR spectrum of 1 in DMSO-d6, while no signal in the 71Ga NMR could be detected

Methanolysis as a Route to Gallium(III) Clusters: Synthesis and Structural Characterization of a Decanuclear Molecular Wheel

Treatment of a methanolic solution of gallium(III) nitrate with lithium hydroxide in the presence of benzilic acid resulted in the decanuclear cluster [Ga(OMe)2{O2CC(OH)Ph2}]10 (1). The metal and the organic components have assembled to form a cyclic molecule that adopts the structure of a wheel. The 10 GaIII ions are approximately coplanar and are coordinated in a distorted octahedral manner by six oxygen atoms. The integrity of the molecular wheel is retained in solution, as evidenced by the 1NMR spectrum of 1 in DMSO-d6, while no signal in the 71Ga NMR could be detected

Convenient Route Leading to Neutral <i>fac</i>-M(CO)₃(NNO) Complexes (M = Re, ^99mTc) Coupled to Amine Pharmacophores

The synthesis and characterization of three neutral tricarbonyl fac-M(CO)3(NNO) (M = Re, 99mTc) complexes based on the picolylamine N,N-diacetic acid (PADA) ligand is reported. One of the two carboxylate groups of the PADA ligand is efficiently and conveniently derivatized with an amine nucleophile through the use of the PADA anhydride. In this work, aniline, benzylamine and pyrrolidine were used as model amine nucleophiles. The rhenium complexes were synthesized using the [NEt4]2[Re(CO)3Br3] precursor and fully characterized by elemental analysis, spectroscopic methods, and X-ray crystallography. The analogous technetium-99m complexes were also prepared quantitatively using the [99mTc(CO)3(H2O)3]+ precursor. The reaction scheme presented for the synthesis of the fac-M(CO)3(NNO) (M = Re, 99mTc) complexes can be applied to the development of target-specific radiopharmaceuticals because, in principle, any bioactive pharmacophore bearing an amine group can be used in the place of the model amine nucleophiles

Reactions of Copper(I) Halides with Tertiary Phosphines. The Unique Structure of [Cu(tribenzylphosphine)₂][CuBr₂]

Reactions of Copper(I) Halides with Tertiary Phosphines. The Unique Structure of [Cu(tribenzylphosphine)2][CuBr2

Reactions of Copper(I) Halides with Tertiary Phosphines. The Unique Structure of [Cu(tribenzylphosphine)₂][CuBr₂]

Reactions of Copper(I) Halides with Tertiary Phosphines. The Unique Structure of [Cu(tribenzylphosphine)2][CuBr2

From Monomer Zinc−Oxamato Complexes to Tetranuclear Inverse 12-Membered and Octanuclear 12-Membered Metallacrowns

Interaction of ZnCl2 with Hpko (Hpko, di-2-pyridyl-ketonoxime) results in the formation of a uninuclear Zn(Hpko)Cl2 (1) compound or in a 12-membered tetranuclear metallacrown (OH)2[inv12-MCZn(II)N(pko)-4]Cl2 (2) depending on the pH of the mother solution. The addition of H3shi (H3shi, salicylhydroxamic acid) leads to the formation of the octanuclear 12-membered tetranuclear metallacrown [Zn2]{[Zn2(pko)4][12-MCZn(II)N(shi)-4](CH3OH)2} (3). The metallacrown core of 2 is characterized as “inverse” because the zinc atoms, rather than oxygen atoms, are oriented toward the central cavity. Two triply bridging hydroxides are accommodated in the center of the metallacrown ring. The pko- ligands form a propeller configuration that imposes absolute stereoisomerism with Λ and Δ chirality. Each hydroxo oxygen bridges two octahedral zinc atoms and a tetrahedral one. The octanuclear cluster Zn8(shi)4(pko)4(CH3OH)2 contains a 12-membered tetranuclear metallacrown core constructed by four Zn metal atoms and four shi3- ligands. So, a part of the cluster can be described as having the formally anionic [12-MCZn(II)N(shi)-4]4- core. Two of the zinc atoms are in octahedral coordination environment while for the other two the geometry is best described as distorted trigonal bipyramidal. The metallacrown core accommodates a binuclear compound with the formula [Zn2(pko)4]. Two of the ring metal ions create binuclear units with two zinc ions, respectively, with two oxamato oxygens, and two phenolato oxygens, of the four interlinked shi3- ligands acting as bridging atoms

Methanolysis as a Route to Gallium(III) Clusters: Synthesis and Structural Characterization of a Decanuclear Molecular Wheel

Treatment of a methanolic solution of gallium(III) nitrate with lithium hydroxide in the presence of benzilic acid resulted in the decanuclear cluster [Ga(OMe)2{O2CC(OH)Ph2}]10 (1). The metal and the organic components have assembled to form a cyclic molecule that adopts the structure of a wheel. The 10 GaIII ions are approximately coplanar and are coordinated in a distorted octahedral manner by six oxygen atoms. The integrity of the molecular wheel is retained in solution, as evidenced by the 1NMR spectrum of 1 in DMSO-d6, while no signal in the 71Ga NMR could be detected

A Two-Dimensional Manganese(II) Carboxylato Polymer. Structure, Magnetism, and EPR Study

The synthesis, crystal structure, and properties of [MnII(MCPA)2(H2O)2]n (MCPA = 2-methyl-4-chlorophenoxyacetic acid), 1, a 2-D manganese carboxylato polymer is reported. The synthesis of 1 has been achieved via the reaction of MCPA with MnCl2·2H2O and NaHCO3 in methanol. Crystal structure data:  [C18H20Cl2O8Mn]; orthorhombic; space group Pbca; a = 7.811(6) Å; b = 34.67(3) Å; c = 7.481(6) Å; Z = 4. The compound has a two-dimensional structure with Mn2+ atoms in an octahedral environment and mixed water/carboxylate coordination. The metal atoms are segregated in planes which are perpendicular to the b axis and are spaced 17.73 Å apart. Variable-temperature magnetic susceptibility measurements indicate the presence of antiferromagnetic behavior. The EPR spectra of polycrystalline samples at 4 K show that the intensity of the signal decreases significantly with decreasing temperature and below ∼4 K becomes EPR silent

Novel Mixed-Valence Manganese Cluster with Two Distinct Mn₃(II/III/II) and Mn₃(III/II/III) Trinuclear Units in a Pseudocubane-like Arrangement

The reaction between Mn(ClO4)2 and di-(2-pyridyl)-ketone in the presence of the sodium salt of propanediol as a base in MeOH leads to the formation of a hexanuclear manganese cluster. This cluster has been characterized by the formula [Mn(II)3Mn(III)3O(OH)(CH3pdol)3(Hpdol)3(pdol)](ClO4)4 (1). Molecular conductance measurements of a 10−3 M solution of compound 1 in CH3CN, DMSO, or DMF give Λm = 529, 135, or 245 μS/cm, respectively, which suggests a 1:4 cation/anion electrolyte. The crystal structure of hexanuclear manganese cluster 1 consists of two distinct trinuclear units with a pseudocubane-like arrangement. The trinuclear units show two different valence distributions, Mn(II)/Mn(III)/Mn(II) and Mn(III)/Mn(II)/Mn(III). Additional features of interest for the compound include the fact that (a) two of the Mn(III) ions show a Jahn−Teller elongation, whereas the third ion shows a Jahn−Teller compression; (b) one bridge between Mn(III) atoms is an oxo (O2−) ion, whereas the bridge between Mn(II) and Mn(III) is a hydroxyl (OH−) group; and (c) the di-(2-pyridyl)-ketone ligand that is methanolyzed to methyl-Hpdol and R2pdol (R = CH3, H) acts in three different modes: methyl-pdol(−1), Hpdol(−1), and pdol(−2). For magnetic behavior, the general Hamiltonian formalism considers that (a) all of the interactions inside the two “cubanes” between Mn(II) and Mn(III) ions are equal to the J1 constant, those between Mn(II) ions are equal to the J2 constant, and those between the Mn(III) ions are equal to the J3 constant and (b) the interaction between the two cubanes is equal to the J4 constant. The fitting results are J1 = J2 = 0.7 cm−1, J3 ≈ 0.0, J4 = −6.2 cm−1, and g = 2.0 (fixed). According to these results, the ground state is S = 1/2, and the next excited states are S = 3/2 and 5/2 at 0.7 and 1.8 cm−1, respectively. The EPR spectra prove that the spin ground state at a low temperature is not purely S = 1/2 but is populated with the S = 3/2 state, which is in accordance with the susceptibility and magnetization measurements