The dinuclear scandium(III) cyclooctatetraenyl chloride complex di-mu-chlorido-bis[(η~8-cycloocta-tetraene)(tetrahydrofuran-kappaO)scandium(III)]

摘要

Only a few cyclooctatetraene dianion (COT) pi-complexes of lanthanides have been crystallographically characterized. This first single-crystal X-ray diffraction characterization of a scandium(III) COT chloride complex, namely di-mu-chlorido-bis[(η~8-cyclooctatetraene)(tetrahydrofuran-kappaO)scandium(III)], [Sc_2 (C_8H_8)_2Cl_2(C_4H_8O)_2] or [Sc(COT)Cl(THF)]_2 (THF is tetrahydrofuran), (1), reveals a dimeric molecular structure with symmetric chloride bridges [average Sc-Cl = 2.5972 (7) A] and a η~8-bound COT ligand. The COT ring is planar, with an average C-C bond length of 1.399 (3) A. The Sc-C bond lengths range from 2.417 (2) to 2.438 (2) A [average 2.427 (2) A]. Direct comparison of (1) with the known lanthanide (Ln) analogues (La, Ce, Pr, Nd, and Sm) illustrates the effect of metal-ion (M) size on molecular structure. Overall, the M- Cl, M-O, and M- C bond lengths in (1) are the shortest in the series. In addition, only one THF molecule completes the coordination environment of the small ScIII ion, in contrast to the previously reported dinuclear Ln-COT-Cl complexes, which all have two bound THF molecules per metal atom.