HoClTe2O5:: A telluriumdioxide-rich holmium(III) chloride oxotellurate(IV)

While attempting to synthesize anionically derivatized holmium oxotellurates by reacting holmium chloride (HoCl3) with tellurium oxide (TeO3; molar ratio 1 : 3, 800 degreesC 10 d) in evacuated silica ampoules, transparent, greenish yellow and coarse single crystals of holmium(III) chloride oxotellurate(IV) HoClTe2O5 (triclinic, P (1) over bar; a = 762.07(6), b = 796.79(6), c = 1010.36(8) pm, alpha = 100.987(4), beta = 99.358(4), gamma = 91.719(4)degrees; Z = 4) were obtained. The crystal structure contains eightfold coordinated (Hol)(3+) (only surrounded by oxygen atoms) and sevenfold coordinated (Ho2)(3+) cations (surrounded by one chloride and six oxide anions). Each sort of holmium polyhedra convenes independently to chains along [100] by edge-sharing which again combine alternately via O6 and O9 to form if (2)(infinity){[Ho2O10(Cl1)](15-)} layers parallel (001). Each of the four crystallographically different Te4+ cations are surrounded by three close oxygen atoms (d(Te-O) = 188 - 195 pm) and always one more situated further away. The stereochemical activity of the non-bonding electron pairs ("lone pairs") leads to psi(l)-trigonal bipyramidal coordination figures. The psi(1)-tetrahedral [TeO3](2-) basic units form discrete [Te2O5](2-) doubles with ecliptic conformation which are arranged in a fish-bone pattern parallel to (001) on both sides of the (2)(infinity){[Ho2O10Cl](15-)} layers. The coherence of the (2)(infinity){[Ho-2(Cl1)Te4O10](+)} layers is exclusively maintained via Cl2-Tel contacts with an extraordinary long distance of 335 pin. As (Cl1)(-) belongs to the coordination sphere of (Ho2)(3+) and (Cl2)(-) is only surrounded by Te4+, the compound should be correctly named holmium(III) chloride oxochlorotellurate(IV) Ho2Cl[Te4O10Cl] (Z = 2).