New Arylene–Germylene–Vinylene Compounds: Stereoselective Synthesis, Characterization, and Photophysical Properties

Highly selective α-hydrogermylation of alkynes catalyzed by an in situ generated bulky NHC-cobalt complex

A new catalytic system, based on an octacarbonyl dicobalt(0) complex and bulky ligand, providing a route to α-vinylgermanes is described. The proposed method can be effectively used for Markovnikov-selective hydrogermylation of a number of terminal and internal alkynes. It has been proved that analogous catalytic systems containing less sterically demanding ligands cannot serve as selective catalysts in this transformation.

Ru(0)-catalysed cross-dimerisation and -trimerisation of alkynyl- with butadienylheteroarenes

Ru(0)-catalysed cross-dimerisation and -trimerisation give a series of di- and triheteroaryl compounds cross-linked by π-conjugated trienyl groups. Their photochemical behaviour is studied using UV-visible absorption spectra, fluorescence emission spectra, and TD-DFT calculations. The cross-trimer prepared from 2,5-dialkynylthiophene with 2 equiv. of 2-butadienylpyridine shows a longer wavelength shift in the absorption maximum than the cross-trimer prepared from dialkynylbenzene with 1-phenylbutadiene. The solvent effect and the TD-DFT calculations suggest that the planarity of the π-conjugated system contributes more than spontaneous polarization. Namely, in the 5-membered thiophene ring, the conjugated trienyl group extends in the same plane (dihedral angle: -4.0°) as the thienyl group, whereas in the 6-membered benzene ring, the planarity is reduced due to steric hindrance (dihedral angle: -24.1°). Thus, the cross-trimers with a 5-membered heteroaryl centre contribute to longer wavelengths of absorption and fluorescence emission due to the increased planarity of the conjugated trienyl groups.

Nickel-Catalyzed Reductive C-Ge Coupling of Aryl/Alkenyl Electrophiles with Chlorogermanes

Cross-electrophile coupling has emerged as a promising tool for molecular synthesis; however, current studies have focused mainly on forging C-C bonds. We report a cross-electrophile C-Ge coupling reaction and thereby demonstrate the possibility of constructing organogermanes from carbon electrophiles and chlorogermanes. The reaction proceeds under mild conditions and offers access to both aryl and alkenyl germanes. Electron-rich, electron-poor, and ortho-/meta-/para-substituted (hetero)aryl electrophiles, as well as cyclic and acyclic alkenyl electrophiles, were coupled. Gram-scale reaction, incorporation of the -GeR₃ moiety into complex biologically active molecules, and derivatization of formed organogermanes are demonstrated.