Structural chemistry and magnetism of dicyclopentadienidehalides of lanthanides. Part 6. Ytterbiumdicyclopentadienidechloride and -bromide, [Yb(C5H5)2Cl]2 and [Yb(C5H5)2Br]2

Abstract The crystal structures of ytterbiumdicyclopentadienidechloride and -bromide, [Yb(C 5 H 5 ) 2 Cl] 2 ( I ) and [Yb(C 5 H 5 ) 2 Br] 2 ( II ), have been determined from X-ray diffraction data. I crystallizes in the [Er(C 5 H 5 ) 2 Cl] 2 -type structure, space group P 2 1 / c , with a =11.021(4), b =7.998(2), c =12.123(4) A, β=110.37(3)°, V =1002(1) A 3 , D c =2.244 g cm −3 and Z =2 dimers. II is isotypic to [Sc(C 5 H 5 ) 2 Cl] 2 (space group P 2 1 / c ) with a =13.968(3), b =16.346(5), c = 13.662(3) A, β=93.78(2)°, V =3112(2) A 3 , D c = 2.452 g cm −3 and Z =6 dimers. The structures have been refined by full matrix least-squares techniques to conventional R factors of 0.037 for 1556 ( I )and 0.031 for 1935 ( II ) reflections (with I >3σ( I )). Magnetic susceptibility data (3.7 T 3+ free ion ground state 2 F 7/2 (idealized symmetry: D 2d ) and a small negative molecular field parameter.