Contact and solvent-separated ion pair aluminium “ate” complexes on a titanium oxide molecular model

Abstract

Treatment of [{Ti(η⁵-C₅Me₅)(μ-O)}₃(μ₃-CR)] [R = H (1), Me (2)] with AlPh₃ or AlMe₃ gives adducts [R′₃Al(μ₃-O)(μ-O)₂{Ti(η⁵-C₅Me₅)}₃(μ₃-CR)] [R = H, R′ = Ph (3), Me (4); R = Me, R′ = Ph (5), Me (6)] that react with LiNMe₂ to give the contact ion pair complexes [Ph₃Al(μ-NMe₂)Li(μ₃-O)₃{Ti(η⁵-C₅Me₅)}₃(μ₃-CR)] [R = H (7), Me (8)] or the solvent-separated ion pair compounds [Li{(μ₃-O)₃Ti₃(η⁵-C₅Me₅)₃(μ₃-CR)}₂][(Me₃Al)₂(μ-NMe₂)] [R = H (9), Me (10)]. Reactions of 1 or 2 with a mixture of AlPh₃ and LiCH₂SiMe₃ lead to the solvent-separated ion pair complexes [Li{(μ₃-O)₃Ti₃(η⁵-C₅Me₅)₃(μ₃-CR)}₂][Al(CH₂SiMe₃)Ph₃] [R = H (11), Me (12)], presumably by evolution of redistribution intermediates containing the lithium dicubane cation [Li{(μ₃-O)₃Ti₃(η⁵-C₅Me₅)₃(μ₃-CR)}₂]⁺ and [Li{Al(μ-Ph)₂Ph(CH₂SiMe₃)}₂]⁻ anionic units. Surprisingly, reaction of 4 with p-tolyl lithium gives the complex [{Me₂Al(μ-Me)Li(p-MeC₆H₄)}{(μ₃-O)₂(μ-O)Ti₃(η⁵-C₅Me₅)₃(μ₃-CH)}] 13 in which the aryl lithium species is incorporated showing interactions with both the trialkyl aluminium unit and the organometallic oxide 1. X-ray diffraction studies were performed on 8, 12 and 13.