Half‐Sandwich Complexes [Cp′₄Ln₄I₈]₄ (Ln=Ce, Pr):Emergence of Donor‐Free Organolanthanide Nanowheels

Abstract

Dedicated to Professor Rinaldo Poli on the occasion of his 65th birthday. Slow diffusion of Me3 SiI into an n-hexane solution of lanthanide half-sandwich complexes [Cp'Ln(AlMe 4 ) 2 ] (Ln=Ce, Pr; Cp'=C 5 H 4 SiMe 3 ) gives access to the hexadecalanthanide ringcluster hybrids [Cp' 4 Ln 4 I 8 ] 4 , along with the cyclopentadienylbridged {Ce 8 } cluster [Cp' 4 Ce 4 I 7 (μ 2 -Cp)] 2 . On the contrary, direct addition of the halogenating reagent to complex [Cp'Ce-(AlMe 4 ) 2 ] in solution affords the spherical dodecanuclear cluster [Cp'CeI 2 ] 12 in addition to [Cp' 4 Ln 4 I 8 ] 4 . The isostructural bromide and chloride clusters [Cp'LnX 2 ] 12 (X=Cl, Br) were isolated via the same solution synthesis protocol, using the mild halogenido transfer reagents Me 3 GeX (X=Cl, Br). The reaction [Cp'Ce-(AlMe 4 ) 2 ]/Me 3 GeCl yielded the decanuclear heteroaluminato derivative [Cp' 5 Ce 5 Cl 9 (AlCl 2 Me 2 )] 2 as a coproduct. Attempts to isolate any intermediate species by performing the reaction at low temperature resulted in incomplete AlMe 4 /iodido exchange, affording the hexanuclear homoaluminate cluster [Cp' 6 Pr 6 I 8 (AlMe 4 ) 4 ]. All cerium clusters show bright photoluminescence under UV light. The luminescence properties of the dodecanuclear clusters [Cp'CeX 2 ] 12 (X=Cl, Br, I) were closer investigated.