Copper complexes of arylselenolate-based ligands: synthesis and catalytic activity in azide–alkyne cycloaddition reactions.

[CuCl₂(PPh₃)₂] reacts with the sodium salt of arylselenolates to yield tetrahedral [CuCl(SeAr)(PPh₃)₂] ((Ar = Ph, 1a; C₅H₄N, 1b; C₄H(4,6-Me)₂N₂), 1c). During crystallization, the pyridyl nitrogens of the latter complexes 1b and 1c were protonated. However, the similar reaction with CuCl₂·2H₂O resulted in the formation of the polymeric complex of composition [Cu(SeAr)₂]_n (Ar = Ph, 2a; C₅H₄N, 2b). The latter complex 2b yielded the mono nuclear [CuCl(SeC₅H₄N)(PPh₃)₂] (1b) on treatment with excess phosphine. All complexes were characterized by elemental analysis, ¹H NMR, IR and mass spectroscopy. The molecular structure of [CuCl(SeC₅H₄N⁺H)(PPh₃)₂] (1b′) was investigated by single crystal X-ray diffraction analysis. The copper(ii) complexes of arylselenolates efficiently catalyzed azide–alkyne cyclo-addition reactions (click reactions) in water to give 1,4-substituted 1,2,3-triazoles in good to moderate yields. [ABSTRACT FROM AUTHOR]