Co-ordination chemistry of higher oxidation states. Part 26. Spectroscopic studies of tellurate complexes of the trivalent Group 1B metals. X-Ray structure of Na5[Cu{TeO4(OH)2}2]·16H2O

Abstract

The structure of Na₅[Cu{TeO₄(OH)₂}₂]·16H₂O has been determined by X-ray structure analysis. It crystallises in the triclinic space group P with a= 5.922(4), b= 8.939(2), c= 12.528(2)Å, α= 98.45(1), β= 99.11(3), γ= 93.82(4)°, and Z= 1. The structure was refined to R= 0.040 for 2 131 observed reflections [F > 3σ(F)]. The composition of the crystal examined was deficient in sodium leading to a proposed formula Na_5–xH_x[Cu{TeO₄(OH)₂}₂]·16H₂O (x= 0.64). The discrete centrosymmetric anion contains Cu^III with approximately square-planar CuO₄ groups linked by trans edges to TeO₄(OH)₂ octahedra [Cu–O 1.833(4) and 1.839(4)Å]. The [M{TeO₄(OH)₂}₂]^5– ions (M = Cu, Ag, or Au) have been studied by i.r., u.v.–visible, and n.m.r. (¹²⁵Te, ¹⁰⁹Ag, and ¹⁷O) spectroscopy. For [Ag{TeO₄(OH)₂}₂]^5– the ¹²⁵Te n.m.r. signal (+774 p.p.m.) is a doublet [²J(^107,109Ag–¹²⁵Te)= 73 Hz]. For the silver(III) ions [Ag{TeO₄(OH)₂}₂]^5– and [Ag{IO₅(OH)}₂]^5– the ¹⁰⁹Ag n.m.r. signals occur at ca.+2 800 p.p.m. from Ag⁺(aq).