The ethenylation of a pyrazolato gallium dichloride dimer: Synthesis of vinyl pyrazolato gallium complexes

•A well soluble bulky pyrazolato-based gallium dichloride dimer is readily prepared.•The pyrazolato-based gallium dichloride activates terminal silyl acetylenes at 110 °C.•The ethynylation gives unusual chelating (N-alkenyl)pyrazolato gallium dichlorides.•The mechanism of ethynylation is likely via an intramolecular electrophilic process.•The reduction of a chelating gallium dichloride yields a Ga(II) species with Ga–Ga bond.

Several monomeric alkenyl-substituted pyrazolato gallium dichloride [(3,5-tBu2-N–CHC(SiR1R2R3)pz)GaCl2] 2(a–d) (R1 = R2 = R3 = Me (2a); R1 = R2 = R3 = Et (2b); R1 = R2 = Me, R3 = tBu (2c); R1 = R2 = Me, R3 = Ph (2d); 3,5-tBu2pz = 3,5-di-tert-butylpyrazolato) were synthesized in good yields by the reaction of dinuclear gallium compound [(η1,η1-3,5-tBu2pz)GaCl2]2 (1) and two equivalents of substituted ethynes. Compound 2a was further reduced with potassium–sodium alloy to afford a gallium(II) complex [(η1-tBu2pz-N–CHC(SiMe3))ClGa]2 with Ga–Ga single bond (3a).

Graphical abstractA vinyl pyrazolato Ga(II) complex with Ga–Ga bond was prepared.Figure optionsDownload full-size imageDownload as PowerPoint slide