Abstract: The title complex Na₄H[Cu(H₂TcO₆)₂]·17H₂O has been obtained from alkaline aqueous solution and its crystal struture was determined by four-cycle X-ray diffractometry. The complex is triclinic and has space group P₁^- with a=0.5930(2)nm, b=0.8957(3)nm, c=0.12555(3)nm, α=98.49(2)°, β=98.98(2), γ=93.94(2)°, V=0.6495(3)nm³, M=913.7, Dc=2.34g/cm³, Z=1. The copper(Ⅲ) ion is chelated by two groups of distorted octahedral TeO₄(OH)₂ to configurate CuO₄ square planar of quasi-D_2h symmetry. The distances of Cu-O is 0.1830 and 0.1844 nm respectively.The UV absorption spectrum of the complex solution shows two bands at 270 nm and 405 nm which are attributed to ligand-metal charge transfer transitions.

Key words: copper(Ⅲ) complex, crystal structure, UV absorption spectrum