Anomeric Effects in Sulfonyl Compounds: An Experimental and Computational Study of Fluorosulfonyl Azide, FSO2N3, and Trifluoromethylsulfonyl Azide, CF3SO2N3.

Fluorosulfonyl azide, FSO2N3, was characterized by IR (gas phase, Ar matrix), and Raman (liquid) spectroscopy. According to the matrix IR spectrum of 18O-labeled FSO2N3, its two oxygen atoms are nonequivalent. This assumption was confirmed by the X-ray crystal structure of FSO2N3at −123 °C, as only one conformer was observed with one of the SO bonds in synperiplanar position to the N3group (ϕ(OS−NN) = −14.8(3)°) with respect to the S−N bond. The same conformation was found for trifluoromethylsulfonyl azide, CF3SO2N3(ϕ(OS−NN) = −23.74(15)°), in the solid state. The preference of such a synperiplanar configuration between SO and N3was rationalized by a predominant anomeric interaction of nσ(N) → σ*(S−O), as supported by the experiment and quantum chemical calculations. [ABSTRACT FROM AUTHOR]