title: A second monoclinic polymorph of 2-(diformyl-methyl-idene)-3,3-dimethyl-2,3-dihydro-1H-indole.
abstract: The crystal structure of the title compound, C(13)H(13)NO(2), is a polymorph of the structure first reported by Helliwell et al. [Acta Cryst. (2006), E62, o737-o738]. It is also monoclinic (space group P2(1)/c), but with completely different cell constants. The mol-ecular conformations of these polymorphs differ by a 180° rotation of one formyl group. The present mol-ecule is planar [maximum deviation 0.089 (2) Å] with the exception of the two methyl groups which lie on either side of the plane. There are strong intra- and inter-molecular N-H⋯O hydrogen bonds. The latter link pairs of mol-ecules across crystallographic centers of symmetry. Two aldehyde O atoms are brought close together [2.896 (4) Å in this arrangement but are not hydrogen bonded. In the earlier polymorph, one formyl group is rotated by 180° to yield inter-molecular hydrogen bonding and an infinite polymeric chain. The other formyl group is involved in the same intra-molecular hydrogen bonding as has been found here.
authors.forename: Hamid
authors.initials: H
authors.lastname: Khaledi
authors.forename: Siti Munirah
authors.initials: SM
authors.lastname: Saharin
authors.forename: Hapipah
authors.initials: H
authors.lastname: Mohd Ali
authors.forename: Ward T
authors.initials: WT
authors.lastname: Robinson
authors.forename: Mahmood A
authors.initials: MA
authors.lastname: Abdulla