Metal halide coordination compounds with quinazolin-4(3 H)-one

Abstract

Three coordination compounds of quinazolin-4(3H)-one (quinoz; C₈H₆N₂O) with divalent group 12 halides are reported. In all complexes, coordination occurs via the nitro-gen atom ortho to the quinazolinone carbonyl group. In the two chain polymers with composition [MX ₂(quinoz)], viz. (M = Cd, X = Br), catena-poly[[[quinazolin-4(3H)-one-κN ³]cadmium(II)]-di-μ-bromido], [CdBr₂(C₈H₆N₂O)]_n (I), and M = Hg, X = Cl, catena-poly[[[quinazolin-4(3H)-one-κN ³]mercury(II)]-di-μ-chlorido], [HgCl₂(C₈H₆N₂O)]_n (II), the divalent cations are five-coordinate, with four bridging halide and one terminal quinoz ligand. The Cd^II atom in (I) has an almost trigonal-bipyramidal coordination environment, whereas the Hg^II atom in (II) has a more distorted coordination environment. Likewise, the halide bridges in (II) are significantly more asymmetric than in (I). In both (I) and (II), quinoz ligands at adjacent cations along each strand are oriented in opposite directions, and the organic ligands of neighboring strands inter-digitate with resulting π-π inter-actions. In contrast to the halide-bridged chain polymers (I) and (II), the adduct of quinoz with CdI₂ is the tetra-hedral complex [CdI₂(quinoz)₂], di-iodido-bis-[quinazolin-4(3H)-one-κN ³]cadmium(II), [CdI₂(C₁₆H₁₂N₄O₂)], (III). The Cd^II atom in this discrete complex is located on a twofold rotation axis. Disorder in (III) is reflected in an alternative minority orientation of the mol-ecules for which the iodine sites closely match the position of the majority orientation. In view of the low site occupancy of only 0.0318 (8) Å, only the Cd^II position for this alternative orientation was taken into account during refinement. In all three compounds, classical N-H⋯O hydrogen bonds with donor-acceptor distances of ca 2.9 Å occur; they link the polymer chains in (I) and (II) into di-periodic networks and connect adjacent discrete complexes in (III) to mono-periodic strands.

Keywords: cadmium(II) coordination polymer; crystal structure; halide-bridged coordination polymers; mercury(II) coordination polymer; quinazolinone coordination; tetra­hedral cadmium(II) complex..