1-Ethyl-5-iodo­indoline-2,3-dione

There are two independent mol­ecules in the asymmetric unit of the title compound, C₁₀H₈INO₂, which differ in the degree of planarity. The iodo­indoline-2,3-dione skeleton of mol­ecule 1 is essentially planar [mean deviation = 0.003 (2) Å for the nine non-H atoms of the indoline core, with a maximum deviation of 0.033 (1) Å for the I atom]. The I atom and O atom in the 3-position of mol­ecule 2 deviate by 0.195 (1) and 0.120 (2) Å, respectively, from the least-squares plane through the nine non-H atoms of the indoline core. Mol­ecules 1 and 2 are roughly coplanar, the mean planes through their cores making a dihedral angle of 6.84 (1)°. This coplanarity results in a layer-like structure parallel to (6,11,17) in the crystal, the distance between adjacent least-squares planes through the cores of mol­ecules 1 and 2 being 3.37 (1) Å. In such a layer, mol­ecules 1 and 2 are linked by C—H...O hydrogen bonds, forming chains along [11-1]. The chains are further coupled to construct a kind of double-chain structure via I...O inter­actions [3.270 (2) Å].