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Reactivity at the β-Diketiminate Ligand Nacnac- on Titanium(IV) (Nacnac- = [Ar]NC(CH3)CHC(CH3)N[Ar], Ar = 2,6-[CH(CH3)2]2C6H3). Diimine-alkoxo and Bis-anilido Ligands Stemming from the Nacnac- Skeleton

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posted on 2003-12-01, 00:00 authored by Falguni Basuli, John C. Huffman, Daniel J. Mindiola
The reaction of ketene OCCPh2 with the four-coordinate titanium(IV) imide (L1)TiNAr(OTf) (L1- = [Ar]NC(CH3)CHC(CH3)N[Ar], Ar = 2,6-[CH(CH3)2]2C6H3) affords the tripodal dimine-alkoxo complex (L2)TiNAr(OTf) (L2- = [Ar]NC(CH3)CHC(O)CPh2C(CH3)N[Ar]). Complex (L2)TiNAr(OTf) forms from electrophilic attack of the β-carbon of the ketene on the γ-carbon of the Nacnac- NCCγCN ring. On the contrary, nucleophiles such as LiR (R- = Me, CH2tBu, and CH2SiMe3) deprotonate cleanly in OEt2 the methyl group of the β-carbon on the former Nacnac- backbone to yield the etherate complex (L3)TiNAr(OEt2), a complex that is now supported by a chelate bis-anilido ligand (L32- = [Ar]NC(CH3)CHC(CH2)N[Ar]). In the absence of electrophiles or nucleophiles, the robust (L1)TiNAr(OTf) template was found to form simple adducts with Lewis bases such as CNtBu or NCCH2(2,4,6-Me3C6H2). Complexes (L2)TiNAr(OTf), (L3)TiNAr(OEt2), and the adducts (L1)TiNAr(OTf)(XY) [XY = CNtBu and NCCH2(2,4,6-Me3C6H2)] were structurally characterized by single-crystal X-ray diffraction studies.