Treatment of 1,3-bis(3'-butylimidazolyl-1'-yl)benzene diiodide with elemental sulfur in the presence of a base produced a bis(N-heterocyclic thione) (NHT) pincer ligand precursor. Its reaction with PdCl2(CH3CN)2 produced chloro[1,3-bis(3'-butylimidazole-2'-thione-κ-S)benzene-κ-C]palladium(ii), a 6,6-fused ring SCS-NHT palladium pincer complex. This air stable compound is, to our knowledge, the first SCS pincer complex that utilizes N-heterocyclic thione (NHT) donor groups. The molecular structures of the ligand precursor and the palladium complex were determined by X-ray crystallography and computational studies provided insight into the interconversion between its rac and meso conformations. The photophysical properties of the complex were established, and its catalytic activity in Suzuki, Heck, and Sonogashira cross-coupling reactions was evaluated.

In this paper, we report the synthesis of a series of novel aliphatic-bridged bisphenol-based benzoxazine monomers comprising four to ten methylene unit spacers (BZ(n)BA). Cationic ring-opening polymerization of these monomers provides flexible polybenzoxazine thermosets with good film forming characteristics under solvent-free processing conditions. The effects of aliphatic bisphenol chain length on polymerization behavior, thermomechanical transitions, and mechanical properties of the polybenzoxazine thermosets are reported. Fourier transform-infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) show the ring-opening polymerization proceeds to high conversion with minimal dependence on spacer chain length. Thermomechanical properties of the pBZ(n)BA thermosets, such as rubbery storage modulus and glass transition temperature (T g ), show a strong dependence on the length of the aliphatic-bridged bisphenol linker where both properties decrease with increasing linker length. In particular, changing the length of the aliphatic-bridged bisphenol linker enables tailoring the T g of the pBZ(n)BA series from 67 C to 101 C, as determined by dynamic mechanical analysis (DMA). Tensile properties of the pBZ(n)BA series exhibit similar trends with Young's modulus decreasing and elongation at break increasing with increasing aliphatic-bridged bisphenol linker length. The pBZ(n)BA materials all show a similar three mode degradation process by thermogravimetric analysis (TGA) consistent with other bisphenol based polybenzoxazines, and additionally exhibit a decrease in char yield with increasing aliphatic chain length owing to a decrease in aromatic content in the thermoset network.

1,3-Bis(3'-butylimidazol-1'-yl)benzene diiodide (2a), 1,3-bis(3'-but-3''-enyl-imidazolium-3'-yl)benzene diiodide (2b), 1,3-bis(3'-pent-4''-enyl-imidazolium-3'-yl)benzene diiodide (2c), 1,3-bis(4'-butyl-1',2',4'-triazolium-1'-yl)benzene diiodide (2d), or 1,3-bis(4'-butyl-1',2',4'-triazolium-1'-yl)benzene dibromide (2e) was reacted with Ag2O yielding unprecedented tetra-N-heterocyclic carbene-Ag(I)-X cubane-type clusters. These were characterized by (1)H and (13)C NMR spectroscopy, ESI-TOF MS, elemental analysis, and X-ray crystallography. Results from VT (13)C NMR spectroscopy and cross-over experiments are consistent with intramolecular exchange suggesting that the Ag(I) complexes are molecular rotors.