Synthesis, Structures, and Reactivity of the First Silylene-Linked Cyclopentadienyl-Phosphido Lanthanide Complexes

Reaction of KPHAr (Ar = C 6 H 2 t Bu 3 -2,4,6) with 1 equiv of Me 2 SiCl(C 5 Me 4 H) in THF afforded Me 2 Si(C 5 Me 4 H)(PHAr) ( 1 ) in 92% isolated yield. Metalation of 1 with 2 equiv of BuLi in THF followed by metathesis reaction with t BuOK gave the corresponding potassium complex [Me 2 Si(C 5 Me 4 )(PAr)K 2 (thf) 4 ] 2 ( 2 ) in 88% isolated yield. Reactions of 2 with 2 equiv of LnI 2 (thf) 2 in THF afforded the corresponding lanthanide(II) complexes Me 2 Si(C 5 Me 4 )(PAr)Ln(thf) 3 (Ln = Sm ( 3, 66%), Yb ( 4, 81%)). Two of the three thf ligands in 3 could be removed under vacuum to give [Me 2 Si(C 5 Me 4 )(PAr)Sm(thf)] ( 3 ‘). Treatment of 3 with hexamethylphosphoric triamide (hmpa) or dimethoxyethane (dme) yielded the corresponding hmpa- or dme-coordinated complex Me 2 Si(C 5 Me 4 )(PAr)Sm(hmpa) 2 ( 5 ) or Me 2 Si(C 5 Me 4 )(PAr)Sm(dme) 2 ( 6 ), respectively. The reaction of 2 equiv of 3 or 3 ‘ with benzophenone in THF afforded the corresponding disamarium(III) benzophenone-dianion complex [Me 2 Si(C 5 Me 4 )(PAr)Sm(thf)] 2 ( μ - η 2 -OCPh 2 ) ( 7 ). Treatment of 3 or 3 ‘ with ICH 2 CH 2 I in toluene easily afforded the corresponding samarium(III) iodide complex [Me 2 Si(C 5 Me 4 )(PAr)Sm( μ -I)(thf)] 2 ( 8 ). The solid structures of all of these compounds, 1 − 8, have been determined by X-ray analyses. The mono(thf)-coordinated Sm(II) complex 3 ‘ was active for the polymerization of ethylene, ε -caprolactone, and 1,3-butadiene under appropriate conditions.