Carbenoids spectra

The synthesis and X-ray crystal structure determination of the cationic acyl complex Cp2Ti(772-COPr1)-[NC-B(C6H5)3] has been described. In the 13C NMR spectrum, the acyl carbon exhibits an unusual highly deshielded chemical shift of S 340.4, consistent with carbenoid character. The complex is pentacoordinated and zwitterionic, with the nitrogen atom of the [NC-B(C6H5)3] anion bound to titanium. (Figure 29).1576... 

A systematic study of the structures of thirteen lithiated hydrocarbons and of eighteen a-halolithium carbenoids in donor solvent (R20, R3N) mixtures down to — 150 °C has been performed by Seebach and coworkers 149,150,151). At room temperature no 13C—6Li coupling was observed in the 13C nmr spectrum because of fast inter- and intra-aggregate exchange processes. At lower temperatures (<—70 °Cj these reactions freeze out thus allowing a correlation of the multiplicities of the signals with the... 

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