Crystal structures and Hirshfeld surface analysis oftrans-bis(thiocyanato-κN)bis{2,4,6-trimethyl-N-[(pyridin-2-yl)methylidene]aniline-κ²N,N′}manganese(II) andtrans-bis(thiocyanato-κN)bis{2,4,6-trimethyl-N-[(pyridin-2-yl)methylidene]aniline-κ²N,N′}nickel(II))

Abstract

Two new mononuclear metal complexes involving the bidentate Schiff base ligand 2,4,6-trimethyl-N-[(pyridin-2-yl)methylidene]aniline (C15H16N2 or PM-TMA), [Mn(NCS)2(PM-TMA)2] (I) and [Ni(NCS)2(PM-TMA)2] (II), were synthesized and their structures determined by single-crystal X-ray diffraction. Although the title compounds crystallize in different crystal systems [triclinic for (I) and monoclinic for (II)], both asymmetric units consist of one-half of the complex molecule, i.e. one metal(II) cation, one PM-TMA ligand, and one N-bound thiocyanate anion. In both complexes, the metal(II) cation is located on a centre of inversion and adopts a distorted octahedral coordination environment defined by four N atoms from two symmetry-related PM-TMA ligands in the equatorial plane and two N atoms from two symmetry-related NCS− anions in a trans axial arrangement. The trimethylbenzene and pyridine rings of the PM-TMA ligand are oriented at dihedral angles of 74.18 (7) and 77.70 (12)° for (I) and (II), respectively. The subtle change in size of the central metal cations leads to a different crystal packing arrangement for (I) and (II) that is dominated by weak C—H...S, C—H...π, and π–π interactions. Hirshfeld surface analysis and two-dimensional fingerprint plots were used to quantify these intermolecular contacts, and indicate that the most significant contacts in packing are H...H [48.1% for (I) and 54.9% for (II)], followed by H...C/C...H [24.1% for (I) and 15.7% for (II)], and H...S/S...H [21.1% for (I) and 21.1% for (II)].