Weak inter­actions in the crystal structures of two indole derivatives

We describe the syntheses and crystal structures of two indole derivatives, namely a second monoclinic polymorph of ethyl 5-chloro-1H-indole-2-carboxyl­ate C(11)H(10)ClNO(2), (I), and ethyl 5-chloro-3-iodo-1H-indole-2-carboxyl­ate, C(11)H(9)ClINO(2), (II). In their crystal structures, both compounds form inversion dimers linked by pairs of N—H⋯O hydrogen bonds, which generate R (2) (2)(10) loops. The dimers are linked into double chains in (I) and sheets in (II) by a variety of weak inter­actions, including π–π stacking, C—I⋯π, C—Cl—π inter­actions and I⋯Cl halogen bonds.