Synthesis and Structure of a 1,3-alternate-Thiacalix[4]arene diamide Derivative

A novel receptor possessing two complexation sites and bearing 1,3-alternate conformation based on thiacalix[4]arene, confirmed by single crystal X-ray analysis, was prepared. The tetrathiacalix[4]arene diamide shows strong intramolecular hydrogen bonding. The binding behavior towards K⁺ and halides has been examined by ¹H NMR titration experiments.     

Reactions of [(Cp)2Ti(NCS)2] as a potential metalloligand; synthesis and physico-chemical investigations of novel heterobimetallic complexes

Summary Bis(cyclopentadienyl)titanium(IV) diisothiocyanate [(Cp)₂-Ti(NCS)₂] reacts with MCl₂ (M = Cu, Pd or Pt), [CuCl(PPh₃)₃], [RuCl₂(PPh₃)₃] and [RuCl₂(DMSO)₄] (DMSO = dimethylsulphoxide) giving solid compounds of stochiometry [(Cp)₂Ti(-NCS)₂MCl₂] (M = Cu, Pd or Pt), [(Cp)₂Ti(-NCS)₂CuCl(PPh₃)], [(Cp)₂Ti(-NCS)₂-RuCl(PPh₃)₂]Cl and [(Cp)₂Ti(-NCS)₂RuCl₂(DMSO)2]. These products have been characterized by physicochemical and spectroscopic methods.     

Mononuclear nitrogen/sulfur-ligated zinc methoxide and hydroxide complexes: investigating ligand effects on the hydrolytic stability of zinc alkoxide species

The synthesis and properties of mononuclear zinc methoxide ([(ebnpa)Zn-OCH3]ClO4) (1) and hydroxide ([(ebnpa)Zn-OH]ClO4) (2) complexes of a new mixed nitrogen/sulfur ligand (ebnpa = N-2-(ethylthio)ethyl-N,N-bis(6-neopentylamino-2-pyridylmethyl)amine) are reported. The structures of 1 and 2 were determined by X-ray diffraction. Each possesses a single zinc-coordinated anion (methoxide or hydroxide) and exhibits an overall trigonal bipyramidal geometry. Structural and spectroscopic studies indicate the presence of two hydrogen-bonding interactions involving the oxygen atom of the zinc-bound anion in each complex. Treatment of [(ebnpa)Zn-OH]ClO4 with CH3OH results in the formation of an equilibrium mixture of 1 and 2. 1H NMR spectroscopic methods were used to examine the equilibrium as a function of temperature, yielding KMe (304 K) = 0.30(8), DeltaHMe = -0.9(1) kcal/mol, and DeltaSMe = -5(1) eu. The negative enthalpy indicates that spontaneous zinc alkoxide formation from a hydroxide precursor occurs in this system at low temperature. Using the experimentally determined DeltaHMe value, we found the homolytic Zn-O bond dissociation energy (BDE) in the Zn-OCH3 unit to be approximately -14 kcal/mol relative to the Zn-O BDE in the Zn-OH unit.     

Self-assembly of flexible supramolecular metallacyclic ensembles: structures and adsorption properties of their nanoporous crystalline frameworks

The syntheses, structures, and N2 adsorption properties of six new supramolecular metallacycles are reported. Flexible ditopic linkers, 1-4, with systematically varied lengths and conformational degrees of freedom were synthesized utilizing ester linkages. They were used in combination with (dppp)M(OTf)2, where M = Pt(II) and Pd(II), and cis-(Me3P)2Pt(OTf)2 to form flexible supramolecular metallacycles 5-10 in 88-98% isolated yields. Their structures were characterized via multinuclear NMR and X-ray crystallography. The metallacycles stack to form porous structures in the crystalline state. The pore dimensions depend on both the phosphorus ligands attached to the metals and the flexible linkers. Adsorption studies on the porous materials show that 5a, 6, 8, and 9 held 11.7, 16.5, 5.7, and 6.8 cm3/g STP of N2 at 77 K, respectively. A guest-exchange study with nitromethane and toluene reveals that the nanopore in 5 is flexible, a property which was transferred from the linker to the supramolecular structure in the solid state.     

Isolation, characterization, and theoretical study of La2@C78

A new metallofullerene, La2@C78, has been synthesized by DC arc discharge method, isolated by high-performance liquid chromatography, and characterized by laser desorption time-of-flight mass spectrometry, UV-vis-NIR absorption, differential pulse voltammetry, 13C NMR spectroscopy, and theoretical calculations. The La2@C78/CS2 solution is dark violet and presents several characteristic absorption features at 647, 561, 533, and 386 nm, with an onset around 1000 nm. With respect to empty D3-C78, the capability of La2@C78 as an electron acceptor or donor is stronger. Addition of 1,1,2,2-tetrakis(2,4,6-trimethylphenyl)-1,2-disirane to La2@C78 photochemically, as well as thermally, affords bis- and mono-adducts. Theoretical studies and 13C NMR spectroscopic analysis of La2@C78 indicate that it possesses a D3h-C78 cage (78:5).     

Reversible carboxylation of N-heterocyclic carbenes

Spectroscopic analysis, thermogravimetric analysis, and crossover experiments performed on a series of imidazolium carboxylates revealed carboxylation was reversible with N-aryl substituted adducts.