Synthesis and properties of Fischer carbene complexes of N,N-dimethylaniline and anisole π-coordinated to chromium tricarbonyl

Publication date: 15 August 2018 Source:Journal of Organometallic Chemistry, Volume 869 Author(s): Nora-ann Weststrate, Shalane Bouwer, Christopher Hassenrück, Nina A. van Jaarsveld, David C. Liles, Rainer F. Winter, Simon Lotz The reaction of lithiated N,N-dimethylaniline π-coordinated to Cr(CO)3 with W(CO)6 and alkylation with [Et3O][BF4] afforded the o-, m- and p-isomers of the σ,π-bimetallic complexes {η6-Me2NC6H4C(OEt)W(CO)5}Cr(CO)3 (o-, 1, m-, 2 and p-isomer, 3). A by-product of the reaction is found by the substitution of a carbonyl ligand in 1 by the aniline nitrogen atom to give {η6-C,N-o-Me2NC6H4C(OEt)W(CO)4}Cr(CO)3 (4). As a result, the W-chelate ring dominates the HOMO rather than the{η6-arene Cr(CO)3} fragment, affecting the site of the first oxidation. Enhanced activation of anisole by π-coordination to Cr(CO)3, and subsequent reactions with nBuLi, W(CO)6 and [Et3O][BF4] gave only o-substituted products {μ,η6:1-o-MeOC6H4C(OEt)W(CO)5}Cr(CO)3 (5), the monocarbene chelate {μ,η6:2-C,O-o-MeOC6H4C(OEt)W(CO)4}Cr(CO)3 (6) by carbonyl substitution, and by reaction of two molar equivalents of these reagents, the unique σ,π-heterotrimetallic biscarbene complex {μ3,η6:1:1-o,o-MeOC6H3(C(OEt)W(CO)5)2}Cr(CO)3 (7). Attempts to synthesise the m- and p-isomers of 5 were unsuccessful due to transmetallation of the lithiated precursors. NMR data confirmed that lithiation and subsequent reactions of m- or p-bromoanisole chromiumtricarbonyl afforded only the ...

Source: Journal of Organometallic Chemistry - June 18, 2018 Category: Chemistry Source Type: research