Ligand dependence of pi-complex character in disilene-palladium complexes

The synthesis and structures of new 16-electron disilene palladium complexes with 2,6-dimethylphenyl isocyanide and phenyldimethylphosphine ligands [L(1)L(2)Pd{(t-BuMe(2)Si)(2)Si=Si(SiMe(2)Bu-t)(2)}, where L(1) = L(2) = PhMe(2)P; L(1) = (cyclohexyl)(3)P, L(2) = 2,6-dimethylphenyl isocyanide; L(1) = L(2) = 2,6-dimethylphenyl isocyanide] are described. Comparison of the X-ray structural parameters around the disilene moiety among these complexes and related bis(trimethylphosphine)(disilene)palladium and 14-electron (tricyclohexylphosphine)(disilene)palladium revealed that the pi-complex character is sensitive to the residual ligands and increases with decreasing the strength of sigma-donation from the ligands.     

Modular Bidentate Hybrid NHC‐Thioether Ligands for the Stabilization of Palladium Nanoparticles in Various Solvents

The synthesis of four different bidentate hybrid NHC‐thioether ligands is presented. The corresponding palladium nanoparticles are stable in various solvents, depending on the ligand used, and show high chemoselectivity in the hydrogenation of olefins. The solubility of the nanoparticles can be switched multiple times depending on the pH value of the solvent. XPS analysis (which shows a subtle shift in the binding energy) was identified as a convenient tool to establish the binding mode of NHC ligands.     

Design of 2′-phenylethynylpyrene excimer forming DNA/RNA probes for homogeneous SNP detection: The attachment manner matters

1-Phenylethynylpyrene fluorophore (1-PEPy) has long-wavelength shifted emission and higher photostability compared to pyrene, retaining, however, pyrene's ability to form excimers. Here we report the synthesis of 2′-O-[3(and 4)-(pyren-1-ylethynyl)benzyl]-uridines and their tandem incorporation into deoxyribo- and 2′-O-Me-ribo-oligonucleotide probes. Excimer forming probes of type NN … NNXXNN … NN (X = 2′-O-[meta(or para)-(pyren-1-ylethynyl)-benzyl]uridine) containing two adjacent fluorescent nucleosides within an oligonucleotide are available in four types (meta-meta; para-meta; meta-para; para-para). Both DNA (N = deoxyribonucleotides) and 2′-O-Me-RNA (N = 2′-O-Me-ribo-nucleotides) probes were synthesized and their hybridization with complementary and singly mismatched DNA and RNA was studied. Several probes show a dramatic response of their excimer-to-monomer intensity ratio upon hybridization. Remarkably, most spectacular fluorescence changes were demonstrated for probes with para-meta and meta-para combination within 2′-O-Me-ribo-oligonucleotides. Using excimer forming probes, three natural SNP in Helicobacter pylori 23S RNA gene (A2144G, A2143G, A2143C) and the wild type gene can be distinguished.     

Radical anion of isolable dialkylsilylene

By the reduction of an isolable dialkylsilylene, 2,2,5,5-[tetrakis(trimethylsilyl)]-1-silacyclopentane-1,1-diyl (1), with cesium, rubidium, potassium, sodium, and lithium 4,4'-di(tert-butyl)biphenylide in DME at low temperatures, the corresponding silylene radical anion 2 was generated as the first persistent silylene radical anion in solution and characterized by ESR spectroscopy. Radical anion 2 is rather stable at -70 degrees C in DME but decomposes rapidly at room temperature with a half-life time of ca. 20 min. The g-factor and 29Si hyperfine splitting constants (hfs's) of 2 are almost independent of the countercations, indicating that 2 exists as a free ion or a solvent-separated ion pair in a polar DME solution. A very small hfs due to the 29Si nucleus of the divalent silicon (3.0 mT) as well as a very large g-factor (2.0077) indicates that an unpaired electron is accommodated in the vacant 3ppi orbital of silylene 1.     

A stable fused bicyclic disilene as a model for silicon surface

We synthesized the first fused bicyclic disilene 1 representing topologically a partial structure of the Si(001) surface up to the third layer. In the solid state, the five-membered rings adopt the envelope conformation, and the Si=Si double bond in 1 exists in the slightly cis-bent form (bent angle theta is 3.6 degrees ) compared to that of the highly cis-bent dimer on the Si(001) surface. Highly symmetric 1H NMR spectral pattern of 1 remains even at -80 degrees C, indicating the facile ring flipping of the bicyclic skeleton in solution. While syn-adduct was obtained in the reaction of 1 with water, anti-addition of chlorine atoms across the Si=Si double bond in 1 was observed in the reaction with carbon tetrachloride. The structural characteristics of the 9,10-phenanthrenequinone adduct 7 are in good accord with those of the proposed structure of the 9,10-phenanthrenequinone molecule adsorbed on the Si(001) surface.