A NEW CONVENIENT PREPARATION OF MONOCYCLOOCTATETRAENYL-LANTHANIDE COMPLEXES FROM METALLIC LANTHANIDES AND OXIDANTS

Treatment of lanthanide metals with cyclooctatetraene in the presence of an equimolar amount of iodine afforded cyclooctatetraenyl-iodolanth anide(III) complexes, LnI(eta8-cot)(thf)n (cot = cyclooctatetraenyl; 1 a: Ln -La, n = 3; 1b: Ln - Ce, n = 3; 1c: Ln = Pr, n = 3; 1d: Ln = Nd, n = 2; 1e: Ln = Sm, n = 1), in modest yields. Bromo and chloro-bridge d dinuclear complexes of samarium, [Sm(mu-X)(cot)(thf)]2 (2: X = Br; 3 : X = Cl), are also prepared by the reaction of samarium metal with cy clooctatetraene in the presence of 1,2-dibromoethane or Ph3PCl2, respe ctively. The reaction of metallic samarium with cyclooctatetraene and diaryl disulfide or diphenyl diselenide in THF afforded cyclooctatetra enyl-thiolate or -selenolate complexes of samarium(III), [Sm(mu-EAr)(e ta8-cot)(thf)n]2 (4a: EAr = SPh, n = 2; 4b: SC6H2Me3-2,4,6, n = 2; 4c: SC6H2iPr3-2,4,6, n = 1; 5: SePh, n - 2). The dimeric structure of 5 w as revealed by X-ray crystallography [monoclinic, space group P2(1)/n with a = 8.500(5), b - 21.805(6), c = 12.042(5) angstrom, beta = 105.9 8(4)degrees, V = 2145(1) angstrom3, Z = 2, R = 0.055 for 2061 reflecti ons with I > 3sigma(I) and 235 parameters]. A samarium(II) complex, [S m(eta8-cot)(thf)]n (6), was also obtained by the direct reaction of sa marium metal with cyclooctatetraene in THF with a catalytic amount of iodine. Reaction of 6 with iodine and diphenyl disulfide afforded 1e a nd 4a, respectively.