SYNTHESIS AND CRYSTAL-STRUCTURE OF COMPOU NDS OF THE TYPE CUM[B5O10] (M=TM3+, LU3+)

Single crystals of the compounds CuM[B5O10] (M = Tm3+(I), Lu3+(II) hav e been obtained by a B2O3 flux technique. Their structures are isotypi c with CuTb[B5O10]. X-ray investigations on single crystals led to the space group C-2v(21) - Iba2 (Nr. 45); I: a = 622,0(2) pm: b = 844,7(1 ) pm; c = 1266,3(4)pm: Z = 4 and II: a = 618,4(1) pm; b = 845,9(2) pm; c = 1260,9(4) pm; Z = 4. The structure contains (1)(infinity)[B5O10]( 5-) chains that include twelve membered rings of boron and oxygen. Eac h ring consists of two tetrahedral BO4 and two planar B2O5 groups and is connected with neighboring rings via the BO4 units. M(3+) (M = Tm3, Lu3+) is eight-coordinated, while Cu2+ is hexa-coordinated by oxygen .