Mixed Allyl–Borohydride Lanthanide Complexes: Synthesis of Ln(BH₄)₂(C₃H₅)(THF)₃ (Ln = Nd, Sm), Characterization, and Reactivity toward Polymerization

New mixed allyl–borohydrido lanthanide complexes Ln­(BH₄)₂(C₃H₅)­(THF)₃ (Ln = Nd (<b>1</b>), Sm (<b>2</b>)) could be prepared in good yield by reacting Ln­(BH₄)₃(THF)₃ (Ln = Sm, Nd) with 1/2 equiv of Mg­(C₃H₅)₂(THF)_<i>x</i>. X-ray structure analysis revealed monomeric structures with two terminal BH₄ ligands, one π-allyl ligand, and three THF molecules. In an assessment of isoprene polymerization, <b>1</b> afforded <i>trans</i>-1,4-polyisoprene in good yield, as a single component or in combination with Mg cocatalyst. Both <b>1</b> and <b>2</b> were found to be extremely active toward ε-caprolactone polymerization

Synthesis of a Fe^IISH Complex Stabilized by an Intramolecular N–H···S Hydrogen Bond, Which Acts as a H₂S Donor

Through use of the reversible protonation of an iron­(II) complex containing a deprotonated carboxamido moiety, we prepared and fully characterized the first hydrogen­(sulfido)­iron­(II) complex stabilized by an intramolecular hydrogen bond, which acts as a H₂S donor in solution

Characterization of Cobalt(III) Hydroxamic Acid Complexes Based on a Tris(2-pyridylmethyl)amine Scaffold: Reactivity toward Cysteine Methyl Ester

Six Co­(III) complexes based on unsubstituted or substituted TPA ligands (where TPA is tris­(2-pyridylmethyl)­amine) and acetohydroxamic acid (<b>A</b>), <i>N</i>-methyl-acetohydroxamic acid (<b>B</b>), or <i>N</i>-hydroxy-pyridinone (<b>C</b>) were prepared and characterized by mass spectrometry, elemental analysis, and electrochemistry: [Co­(III)­(TPA)­(A-2H)]­(Cl) (<b>1a</b>), [Co­(III)­((4-Cl₂)­TPA)­(A-2H)]­(Cl) (<b>2a</b>), [Co­(III)­((6-Piva)­TPA)­(A-2H)]­(Cl) (<b>3a</b>), [Co­(III)­((4-Piva)­TPA)­(A-2H)]­(Cl) (<b>4a</b>) and [Co­(III)­(TPA)­(B–H)]­(Cl)₂ (<b>1b</b>), and [Co­(III)­(TPA)­(C–H)]­(Cl)₂ (<b>1c</b>). Complexes <b>1a</b>–<b>c</b> and <b>3a</b> were analyzed by ¹H NMR, using 2D (¹H, ¹H) COSY and 2D (¹H, ¹³C) HMBC and HSQC, and shown to exist as a mixture of two geometric isomers based on whether the hydroxamic oxygen was <i>trans</i> to a pyridine nitrogen or to the tertiary amine nitrogen. Complex <b>3a</b> exists as a single isomer that was crystallized. Its crystal structure revealed the presence of an H-bond between the pivaloylamide and the hydroximate oxygen. Complexes <b>1a</b>, <b>2a</b>, and <b>4a</b> are irreversibly reduced beyond −900 mV versus SCE, while complexes <b>1b</b> and <b>1c</b> are reduced at less negative values of −330 and −190 mV, respectively. The H-bond in <b>3a</b> increased the redox potential up to −720 mV. Reaction of complex <b>1a</b> with l-cysteine methyl ester CysOMe was monitored by ¹H NMR and UV–vis at 2 mM and 0.2 mM in an aqueous buffered solution at pH 7.5. Complex <b>1a</b> was successively converted into an intermediate [Co­(III)­(TPA)­(CysOMe-H)]²⁺, <b>1d</b>, by exchange of the hydroximate with the cysteinate ligand, and further into Co­(III)­(CysOMe-H)₃, <b>5</b>. An authentic sample of <b>1d</b> was prepared and thoroughly characterized. A detailed ¹H NMR analysis showed there was only one isomer, in which the thiolate was <i>trans</i> to the tertiary amine nitrogen

Novel 1,2,4-Thiadiazole Derivatives: Crystal Structure, Conformational Analysis, Hydrogen Bond Networks, Calculations, and Thermodynamic Characteristics of Crystal Lattices

The results of X-ray crystallographic and computational studies of twelve 1,2,4-thiadiazole derivatives are reported. The effect of orientation of different parts of the molecules on crystal organization and hydrogen bond network were studied. DFT calculations were carried out in order to explore conformational preferences of the molecules inside and outside of crystal environment. The role of hydrogen bonds was found to be essential for the stabilization of conformationally strained molecules as well as for the packing density of such molecules in a crystal. Thermodynamic aspects of sublimation processes of the studied compounds were analyzed using temperature dependencies of their vapor pressure. Thermophysical characteristics of the molecular crystals were obtained and compared with the sublimation enthalpy and the structural parameters. The influence of crystal structure features on the sublimation enthalpy and on the melting temperature was analyzed

Base-Promoted Expedient Access to Spiroisatins: Synthesis and Antitubercular Evaluation of 1<i>H</i>‑1,2,3-Triazole-Tethered Spiroisatin–Ferrocene and Isatin–Ferrocene Conjugates

The use of sodium hydride provides a convenient access to the synthesis of C-5-functionalized spiroisatins with the absence of the typical drawbacks associated with conventional protocols. The synthesized precursors, viz. <i>N</i>-alkylazido spiroisatins and their unprotected counterparts, were explored in Cu-mediated azide–alkyne cycloaddition reactions to probe the antitubercular structure–activity relationships (SAR) within the isatin–ferrocene–triazole conjugate family. The antitubercular evaluation studies of the synthesized conjugates revealed an improvement in the minimal inhibitory concentration (MIC) with the introduction of ferrocene nucleus, as evidenced by spiroisatin–ferrocene and isatin–ferrocene hybrids

Characterization of Cobalt(III) Hydroxamic Acid Complexes Based on a Tris(2-pyridylmethyl)amine Scaffold: Reactivity toward Cysteine Methyl Ester

Six Co­(III) complexes based on unsubstituted or substituted TPA ligands (where TPA is tris­(2-pyridylmethyl)­amine) and acetohydroxamic acid (<b>A</b>), <i>N</i>-methyl-acetohydroxamic acid (<b>B</b>), or <i>N</i>-hydroxy-pyridinone (<b>C</b>) were prepared and characterized by mass spectrometry, elemental analysis, and electrochemistry: [Co­(III)­(TPA)­(A-2H)]­(Cl) (<b>1a</b>), [Co­(III)­((4-Cl₂)­TPA)­(A-2H)]­(Cl) (<b>2a</b>), [Co­(III)­((6-Piva)­TPA)­(A-2H)]­(Cl) (<b>3a</b>), [Co­(III)­((4-Piva)­TPA)­(A-2H)]­(Cl) (<b>4a</b>) and [Co­(III)­(TPA)­(B–H)]­(Cl)₂ (<b>1b</b>), and [Co­(III)­(TPA)­(C–H)]­(Cl)₂ (<b>1c</b>). Complexes <b>1a</b>–<b>c</b> and <b>3a</b> were analyzed by ¹H NMR, using 2D (¹H, ¹H) COSY and 2D (¹H, ¹³C) HMBC and HSQC, and shown to exist as a mixture of two geometric isomers based on whether the hydroxamic oxygen was <i>trans</i> to a pyridine nitrogen or to the tertiary amine nitrogen. Complex <b>3a</b> exists as a single isomer that was crystallized. Its crystal structure revealed the presence of an H-bond between the pivaloylamide and the hydroximate oxygen. Complexes <b>1a</b>, <b>2a</b>, and <b>4a</b> are irreversibly reduced beyond −900 mV versus SCE, while complexes <b>1b</b> and <b>1c</b> are reduced at less negative values of −330 and −190 mV, respectively. The H-bond in <b>3a</b> increased the redox potential up to −720 mV. Reaction of complex <b>1a</b> with l-cysteine methyl ester CysOMe was monitored by ¹H NMR and UV–vis at 2 mM and 0.2 mM in an aqueous buffered solution at pH 7.5. Complex <b>1a</b> was successively converted into an intermediate [Co­(III)­(TPA)­(CysOMe-H)]²⁺, <b>1d</b>, by exchange of the hydroximate with the cysteinate ligand, and further into Co­(III)­(CysOMe-H)₃, <b>5</b>. An authentic sample of <b>1d</b> was prepared and thoroughly characterized. A detailed ¹H NMR analysis showed there was only one isomer, in which the thiolate was <i>trans</i> to the tertiary amine nitrogen

Isolation of the Large {Actinide}₃₈ Poly-oxo Cluster with Uranium

By controlling the water content, a new poly-oxo-metalate species containing 38 uranium centers has been solvothermally synthesized in the presence of benzoic acid in tetrahydrofuran (THF). The {U₃₈} motif contains a distorted UO₂ core of fluorite type, stabilized by benzoate and THF molecules. This compound is analogous to the {Pu₃₈} motif and was characterized by X-ray photoelectron spectroscopy and magnetic analyses

Base-Promoted Expedient Access to Spiroisatins: Synthesis and Antitubercular Evaluation of 1<i>H</i>‑1,2,3-Triazole-Tethered Spiroisatin–Ferrocene and Isatin–Ferrocene Conjugates

The use of sodium hydride provides a convenient access to the synthesis of C-5-functionalized spiroisatins with the absence of the typical drawbacks associated with conventional protocols. The synthesized precursors, viz. <i>N</i>-alkylazido spiroisatins and their unprotected counterparts, were explored in Cu-mediated azide–alkyne cycloaddition reactions to probe the antitubercular structure–activity relationships (SAR) within the isatin–ferrocene–triazole conjugate family. The antitubercular evaluation studies of the synthesized conjugates revealed an improvement in the minimal inhibitory concentration (MIC) with the introduction of ferrocene nucleus, as evidenced by spiroisatin–ferrocene and isatin–ferrocene hybrids

Novel 1,2,4-Thiadiazole Derivatives: Crystal Structure, Conformational Analysis, Hydrogen Bond Networks, Calculations, and Thermodynamic Characteristics of Crystal Lattices

The results of X-ray crystallographic and computational studies of twelve 1,2,4-thiadiazole derivatives are reported. The effect of orientation of different parts of the molecules on crystal organization and hydrogen bond network were studied. DFT calculations were carried out in order to explore conformational preferences of the molecules inside and outside of crystal environment. The role of hydrogen bonds was found to be essential for the stabilization of conformationally strained molecules as well as for the packing density of such molecules in a crystal. Thermodynamic aspects of sublimation processes of the studied compounds were analyzed using temperature dependencies of their vapor pressure. Thermophysical characteristics of the molecular crystals were obtained and compared with the sublimation enthalpy and the structural parameters. The influence of crystal structure features on the sublimation enthalpy and on the melting temperature was analyzed

Novel 1,2,4-Thiadiazole Derivatives: Crystal Structure, Conformational Analysis, Hydrogen Bond Networks, Calculations, and Thermodynamic Characteristics of Crystal Lattices

The results of X-ray crystallographic and computational studies of twelve 1,2,4-thiadiazole derivatives are reported. The effect of orientation of different parts of the molecules on crystal organization and hydrogen bond network were studied. DFT calculations were carried out in order to explore conformational preferences of the molecules inside and outside of crystal environment. The role of hydrogen bonds was found to be essential for the stabilization of conformationally strained molecules as well as for the packing density of such molecules in a crystal. Thermodynamic aspects of sublimation processes of the studied compounds were analyzed using temperature dependencies of their vapor pressure. Thermophysical characteristics of the molecular crystals were obtained and compared with the sublimation enthalpy and the structural parameters. The influence of crystal structure features on the sublimation enthalpy and on the melting temperature was analyzed