N-trimetylsilyl carboxamides RC(O)NHSiMe3 (R = Me, CF3, Ph): X-ray, DFT and FTIR study

• The synthesis of N-trimethylsilyl trifluoroacetamide 2 was described.
• Crystal structures of N-trimetylsilylacetamide 1, trifluoroacetamide 2 and benzamide 3 have been determined.
• Influence of Si atom on intermolecular electron interactions in amides 1–3 was investigated by theoretical methods.
• Self-association processes and types of dimers in inert media (CCl4) of amides 1–3 were studied.

The X-ray single-crystal structures of N-trimetylsilyl acetamide CH3CONHSiMe3 (1), N-trimethylsilyl trifluoroacetamide CF3CONHSiMe3 (2) and N-trimethylsilyl benzamide PhCONHSiMe3 (3) have been determined. Quantum chemical calculations (B3LYP/6-311+G**, NBO analysis) were performed for gas phase optimized structures, proton affinities and N–H bond dissociation energies of amides 1–3 and their isostructural carbon analogs 4–6. The effect of silicon atom on structural features and intermolecular electron interactions was determined. Types of self-associates which can be formed by amides 1–3 in CCl4 solution were studies by infrared spectroscopy.

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