Crystal structure of (4R,5S,6R)-6-azido-5-benz­yloxy-3,3,4-tri­fluoro­azepan-1-ium 2,2,2-tri­fluoro­acetate from synchrotron data

The structure of the title compound, C(15)H(16)F(6)N(4)O(3), was determined using synchrotron radiation on an extremely small crystal (0.015 × 0.01 × 0.01 mm). Although the diffraction was weak, leading to high residuals and a poor data-to-parameter ratio, the data allowed ready solution and refinement to reveal the entire structure. The solid-state structure is in accordance with the absolute configuration assigned based on that of the known starting material. The compound comprises a highly substituted seven-membered N-heterocyclic cation and a tri­fluoro­methane­sulfonate counter-anion. The title compound crystallizes with two independent cations (A and B) and anions (C and D) in the asymmetric unit. Two geminal F atoms, a single F atom, a benzyl ether and an azide group are substituted on consecutive C atoms between the NH(2) and CH(2) units of the azepan-1-ium ring system. The seven-membered rings adopt different conformations with the principal differences occurring in the CF(2)CHFCH(2) segments of the ring systems. The geminal F atoms on the quaternary C atom exhibit essentially identical bond angles [109 (2) and 106 (2)°] in the two independent mol­ecules. The two mol­ecules associate as a dimeric unit via two C—H⋯F inter­actions. An extensive series of N—H⋯O, N—H⋯F, C—H⋯O, C—H⋯N, C—H⋯F and C—H⋯π contacts generate a three-dimensional network with cations and anions linked into ABCD repeat columns along a.