Synthesis, characterization, and the role of counterion in stabilizing trigonal pyramidal copper(I)/2,2′bipyridine complexes containing electron-poor methyl acrylate

Copper(I)/2,2′-bipyridine complexes, [Cu^I(bpy)(π-CH₂CHCOOCH₃)][A] have been synthesized and characterized. These complexes are used in copper(I) mediated cyclopropanation and aziridination reactions of methyl acrylate and represent the first class of trigonal pyramidal copper(I) complexes with π-coordinated electron poor olefins. In the case of 1 and 3, weak coordination of the counterion was observed. The counterion was noncoordinating in complex 2, which was dimeric in the solid state with the oxygen atoms of the carbonyl moieties in methyl acrylate bridging two copper(I) centers.     

Structural characterization and ferroelectric ordering in (C3N2H5)5Sb2Br11

A ferroelectric crystal (C₃N₂H₅)₅Sb₂Br₁₁ has been synthesized. The single crystal X-ray diffraction studies (at 300, 155, 138 and 121 K) show that it is built up of discrete corner-sharing bioctahedra and highly disordered imidazolium cations. The room temperature crystal structure has been determined as monoclinic, space group, P2₁/n with: , and and β=96.19^°. The crystal undergoes three solid-solid phase transitions: ) discontinuous, continuous and discontinuous. The dielectric and pyroelectric measurements allow us to characterize the low temperature phases III and IV as ferroelectric with the Curie point at 145 K and the saturated spontaneous polarization value of the order of along the a-axis (135 K). The ferroelectric phase transition mechanism at 145 K is due to the dynamics of imidazolium cations.     

Synthesis of trifluoromethylated pyrazoles from trifluoromethylenaminones and monosubstituted hydrazines

Cyclocondensation of monosubstituted hydrazines 2a-c with trifluoromethylenaminones 1a-c afforded 3-CF₃ and (or) 5-CF₃ pyrazoles 3-6. Addition of N-methylhydrazine to enaminone led to 3-CF₃ pyrazole as the major product, whereas phenylhydrazine gave regiospecific formation of 5-CF₃ pyrazole.Structural assignment of regioisomers is based on NMR chemical shifts, long-range carbon-fluorine and hydrogen-fluorine coupling constants and - NOE.The pyrazole 4ac was characterized by X-ray diffraction analysis.     

Low-temperature flux syntheses and characterizations of two 1-D anhydrous borophosphates: Na3B6PO13 and Na3BP2O8

Two new anhydrous sodium borophosphates with one-dimensional structure, Na₃B₆PO₁₃(1) and Na₃BP₂O₈(2), were synthesized by low-temperature molten salts techniques using boric acid and sodium dihydrogen phosphate as flux, respectively. The crystal structures were solved by means of single-crystal X-ray diffraction (1, orthorhombic, Pnma (no. 62), , , , Z=4; 2 , monoclinic, C2/c (no. 15), , , , β=92.492(5)°, Z=8). Compound 1 is characterized by an infinite chain of containing eight-membered rings in which all vertexes of borate groups contribute to interconnection. Compound 2 reveals an infinite straight chain built of vertex-sharing four-membered rings, and chains in neighboring layers arranged along different orientations. The relations between structures and the synthetic conditions with only traced water are discussed.     

Crystal growth, characterization and physical properties of PrNiSb3, NdNiSb3 and SmNiSb3

The crystal structures of three new intermetallic ternary compounds in the LnNiSb₃ (Ln=Pr, Nd and Sm) family have been characterized by single crystal X-ray diffraction. PrNiSb₃, NdNiSb₃ and SmNiSb₃ all crystallize in an orthorhombic space group, Pbcm (No. 57), Z=12, with , , , and ; , , , and ; and , , , and , for Ln=Pr, Nd and Sm, respectively. These compounds consist of rare-earth atoms located above and below layers of nearly square, buckled Sb nets, along with layers of highly distorted edge- and face-sharing NiSb₆ octahedra. Resistivity data indicate metallic behavior for all three compounds. Magnetization measurements show antiferromagnetic behavior with (PrNiSb₃), 4.6 K (NdNiSb₃), and 2.9 K (SmNiSb₃). Effective moments of 3.62 μ_B, 3.90 μ_B and 0.80 μ_B are found for PrNiSb₃, NdNiSb₃ and SmNiSb₃, respectively, and are consistent with Pr³⁺ (f ²), Nd³⁺ (f ³), and Sm³⁺ (f ⁴).     

Ruthenium (II) complexes of the chelating phosphine borane H2ClB · dppm

Reaction of H₂ClB · PPh₂CH₂PPh₂ (H₂ClB · dppm) with results in displacement of all three acetonitrile ligands and the formation of (1), which has been characterised crystallographically. Reaction with carbon monoxide results in a change from η² to η¹ of the borane ligand to afford (2). Compound 1 undergoes H/D exchange under a D₂ atmosphere to afford , while 2 does not.     

Synthesis and characterization of the rare-earth dicyanamides Ln[N(CN)2]3 with Ln=La, Ce, Pr, Nd, Sm, and Eu

The rare-earth dicyanamides Ln[N(CN)₂]₃ (Ln=La, Ce, Pr, Nd, Sm, Eu) were obtained via ion exchange in aqueous medium and subsequent drying: The crystal structures were solved and refined based on X-ray powder diffraction data and they were found to be isotypic: Ln[N(CN)₂]₃; Cmcm (no. 63), Z=4, Ln=La: , , ; Ce: , , ; Pr: , , ; Nd: , , ; Sm: , , ; Eu: , , ). The compounds represent the first dicyanamides with trivalent cations. The Ln³⁺ ions are coordinated by three bridging N atoms and six terminal N atoms of the dicyanamide ions forming a three capped trigonal prism. The structure type is related to that of PuBr₃. The novel compounds Ln[N(CN)₂]₃ have been characterized by IR and Raman spectroscopy (Ln=La) and the thermal behavior has been monitored by differential scanning calorimetry (Ln=Ce, Nd, Eu).     

Layered metal phosphonates containing pyridyl groups: Syntheses and characterization of Mn2(2-C5H4NPO3)2(H2O) and Zn(6-Me-2-C5H4NPO3)

This paper reports the syntheses and characterization of two phosphonate compounds with layered structures, namely, Mn₂(2-C₅H₄NPO₃)₂(H₂O) (1) and Zn(6-Me-2-C₅H₄NPO₃) (2). In compound 1, double chains are found in which the {Mn₂O₂} dimers are linked by both aqua and O-P-O bridges. These double chains are connected through corner-sharing of {MnO₅N} octahedra and {CPO₃} tetrahedra, forming an inorganic layer. The pyridyl groups fill the inter-layer spaces. In compound 2, each {ZnO₃N} tetrahedron is vertex-shared with three {CPO₃} tetrahedra and vice versa, hence forming an inorganic honeycomb layer. The pyridyl groups reside between the layers. Magnetic studies show that weak antiferromagnetic interactions are mediated between the manganese ions in compound 1. Crystal data for 1: monoclinic, space group C2/c, , , , β=107.3(1)°. For 2: orthorhombic, space group Pbca, , , .     

Design and synthesis of four coordination polymers generated from 2,2′-biquinoline-4,4′-dicarboxylate and aromatic bidentate ligands

Four coordination polymers [Zn(bqdc)(phen)]_n (1), [Zn(bqdc)(bpy)(H₂O)]_n (2), [Mn(bqdc)(bpy)(H₂O)₂]_n (3) and [Mn(bqdc)(phen)(H₂O)₂]_n (4) (H₂bqdc=2,2′-biquinoline-4,4′-dicarboxylic acid, phen=1,10-phenanthroline and bpy=2,2′-bipyridyl) have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. Crystal data for 1: monoclinic system, C2/c, , , , β=103.78(3)°, , Z=4. Crystal data for 2: monoclinic system, p2₁/n, , , , β=107.13(7)°, , Z=4. Crystal data for 3: monoclinic system, C2/c, , , , β=116.8010(11)°, , Z=4. Crystal data for 4: monoclinic system, C2/c, , , , β=117.04(3)°, , Z=4. Single helix-like chains exist in 1. The supramolecular structure of 1 exhibits extended two-dimensional network while 2-4 display extended three-dimensional architectures based on interchain hydrogen bonding and π-π interactions. Compounds 1 and 2 show blue photoluminescence under UV light suggesting that they may be employed to develop luminescent materials. Compounds 3 and 4 show interesting magnetic behaviors.     

Syntheses and crystal structures of three new borates templated by transition-metal complexes in situ

Three new cobalt borate compounds, [Co(DIEN)₂][B₅O₆(OH)₄]₂ (DIEN=diethylenetriamine) (1), [B₅O₇(OH)₃Co(TREN)] (TREN=tris(2-aminoethyl)amine) (2), and [Co₂(TETA)₃][B₅O₆(OH)₄]₄ (TETA=triethylenetetramine) (3) have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, IR, elemental analysis and thermogravimetry. The structures exhibit interesting 3D supramolecular hydrogen-bonded architectures, involving the similar borate polyanion [B₅O_6+n(OH)_4−n]⁽ⁿ⁺¹⁾⁻(n=0 for 1 and 3, and n=1 for 2) and the templating transition metal complexes which are generated in situ under mild solvothermal conditions. Crystal data: 1, monoclinic, space group C2/m (No. 12), , , , β=93.601(4)°, , Z=2; 2, monoclinic, P2₁/c (No. 14), , , , β=99.926(4)°, , Z=4; 3, triclinic, space group P-1 (No. 2), , , , α=77.009(5)°, β=80.095(2)°, γ=82.334(3)°, , Z=2.     

Quaternary ammonium salt-based chromogenic and fluorescent chemosensors for fluoride ions

Chemosensors 5-7 possessing a quaternary ammonium cation (for electrostatic interactions) and an N-H group(s) (for H-bonding) as recognition sites and an anthracene-9,10-dione as both a chromogenic and fluorescent moiety exhibit absorption and emission changes with fluoride ions only. No significant response to other anions such as Cl⁻, Br⁻, I⁻, , CH₃COO⁻, , and is observed. The dual emission at λ_max 580 nm (free 5/6) and λ_max 510 and 540 nm (5/6 + F⁻) in chemosensors 5 and 6 enables ratiometric analysis of fluoride ions.     

ipso-and para-Functionalization of meta-terphenyl ligands with substituted methyl groups: Unusual head-to-tail coupling of terphenyl moieties

The synthesis and characterization of several ipso-functionalized derivatives of the bulky terphenyl group are described. These include the primary alcohol Ar′CH₂OH (1), the bromo derivative Ar′CH₂Br (2), and the terphenyl formate Ar′CH₂OC(O)H (3). The alcohol 1 was obtained by treatment of LiAr′ with formaldehyde, and 1 was readily converted to the bromo derivative 2 using HBr. The reaction of 1 with formic acid afforded 3 in good yield. Attempts to form the Grignard derivative of 1, i.e., Ar′CH₂MgBr, resulted in a head-to-tail reaction of the terphenyl benzyl units to yield an unusual coupled product 4. An approach to the avoidance of this coupling involved the synthesis of the terphenyl derivatives and , bearing methyl groups in the para positions of the central aryl ring, which could be prepared in good yield, and converted to their respective lithium salts 7 and 8 without complication . The compounds were characterized by ¹H and ¹³C NMR spectroscopy, IR spectroscopy (1) and X-ray crystallography (2, 4, 5 and 6).     

The variety of reactions of radical cations derived from 2-diphenylaminothiophene oligomers

ESR spectroelectrochemical measurements of 2-diphenylamino-substituted oligothiophenes 8_m proved the existence of radical cations upon oxidation. Their stability and dimerization depend significantly on the number m of thiophene units. The radical cations and are very reactive and dimerize spontaneously to yield either 2,5-bis(diphenylamino)-2,2′-bithiophene 10₂ or 2,5-bis(diphenylamino)-5,5′-bis(2-thienyl)-3,3′-bithiopene 11₂, respectively. In contrast, the radical cations are highly stable and do not dimerize at all.