Gd10I16(C-2)(2) and Gd10Br15B2/Tb10Br15B2 cluster compounds with M-10 twinoctahedra

The compound Gd10I16(C-2)(2) can be prepared from Gd metal, GdI3 and C at 9 50 degrees C. It crystallizes in P (1) over bar with a = 10.463(4) Angstrom , b = 16.945(6) Angstrom, c = 11.220(4) Angstrom, alpha = 99.15(3)degrees, beta = 92.68(3)degrees und gamma = 88.06(3)degrees Gd10Br15B2 is formed bet ween 900 und 950 degrees C, Tb10Br15B2 between 900 und 930 degrees C from s toichiometric amounts of the rare earth metals, tribromide and boron. Both compounds crystallize in the space group P (1) over bar for Gd10Br15B2 with a = 8.984(2) Angstrom, b = 9.816(2) Angstrom, c = 10.552(5) Angstrom, alph a = 91.14(3)degrees, beta = 114.61(3)degrees and gamma = 110.94(3)degrees a nd for Tb10Br15B2 with a = 8.939(4) Angstrom, b = 9.788(3) Angstrom, c = 10 .502(2) Angstrom, alpha = 91.19(3)degrees, beta = 114.51(3)degrees and gamm a = 111.10(2)degrees. In the crystal structures of all three compounds the rare earth metals form edge-shared Ln(10) twin octahedra. In Gd10I16(C-2)(2 ) the Gd octahedra are centered with C-2 groups (d(C-C) = 1.43(7) Angstrom) . In Ln(10)Br(15)B(2) (Ln = Gd, Tb) the octahedra contain single boron atom s. The clusters are connected through halide atoms to chains [Ln(10)(Z)(2)( X4X4/2i-iX2i-a)-X-i]. Adjacent chains are fused threedimensionally via I2i- aI6i-a for the Gd iodide carbide and via Br2/2i-iBr6i-a for the bromide bor ides of Gd und Tb. It is interesting to see an identical pattern of connect ion between the chains for the reduced oxomolybdates, e. g. PbMo5O8.