Synthesis, structures, and reactivity of the first silylene-linked cyclopentadienyl-phosphido lanthanide complexes

Reaction of KPHAr (Ar = (C6H2Bu3)-Bu-t-2,4,6) with 1 equiv of Me2SiCl(C5Me4H) in THF afforded Me2Si(C5Me4H)(PHAr) (1) in 92% isolated yield. Metalation of 1 with 2 equiv of BuLi in THF followed by metathesis reaction with (BuOK)-Bu-t gave the corresponding potassium complex [Me2Si(C5Me4)(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 Me2Si(C5Me4)(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 [Me2Si(C5Me4)(PAr)Sm(thf)] (3'). Treatment of 3 with hexamethylphosphoric triamide (hmpa) or dimethoxyethane (dme) yielded the corresponding hmpa- or dme-coordinated complex Me2Si(C5Me4)(PAr)Sm(hmpa)(2) (5) or Me2Si(C5Me4)(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 [Me2Si(C5Me4)(PAr)Sm(thf)(2)(mu-eta (2)-OCPh2) (7). Treatment of 3 or 3' with ICH2CH2I in toluene easily afforded the corresponding samarium(III) iodide complex [Me2Si(C5Me4)(PAr)Sm(mu -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, epsilon -caprolactone, and 1,3-butadiene under appropriate conditions.