Reactions and effect of N-sulfonylpyrrole yielding metal complexes: Crystal structural studies Winston Nxumalo a,⇑ , Andrew Dinsmore b , Richard M. Mampa a , Bernard Omondi c a Department of Chemistry, University of Limpopo Turfloop Campus, Limpopo, Private Bag X1106, Sovenga, 0727, South Africa b School of Chemistry, University of the Witwatersrand, PO Wits, Johannesburg 2050, South Africa c Department of School of Chemistry and Physics, University of Kwazulu-Natal, Westville Campus, Private Bag X01, Scottsville, 3209, South Africa article info Article history: Received 21 February 2017 Accepted 25 March 2017 Available online 6 April 2017 Keywords: Pyrrole Schiff base ligands X-ray determination structure Anticancer activity Coordination N-Sulfonylpyrrole abstract The reaction of N-toluenesulfonylpyrrole with benzonitrile at room temperature afforded 4-methyl-N- [phenyl(1H-pyrrol-2yl)methylene]toluenesulfonamide (L). The ligand (L) was reacted with selected first, second and third row transition metal salts in low oxidation states, in a basic medium, to afford com- plexes in different coordination modes ranging from three to five coordinated systems. Complexes of the type NiL 2 (2), CuL 2 (3), CuL[P(pH 3 )] (7), AgL[P(pH 3 )] 2 (8), AgL[P(Ph) 3 ](9), and PtL(COD) (10) with unu- sual g 2 ,g 2 to g 2 ,g 1 rearrangement, following double bond migration to form 1,2-g 2 -r-cycloocta-1,4-dienyl r/p coordinating bidentate ligand, were achieved. The reaction of L in the presence of excess DBU afforded a bis-coordinated complexes of the type CoL 2 (DBU) (4) and ZnL 2 (DBU) (5). All compounds were structurally characterised by different techniques including 1 H and 13 C NMR, UV–Vis, IR, Mass spectrom- etry and elemental analysis. The molecular structures of the ligand L and complexes 4, 7, 8, 9 and 10 were determined by X-ray diffraction analysis. In all metal complexes, L behaved as a bidentate chelating ligand through the sulfonylimine nitrogen and the pyrrole nitrogen. Complexes 6, 8 and 9 exhibited mod- erate activity against HeLa cell lines, with 8 showing the highest activity with IC 50 of 3.6 lM, 9 (4.3 lM) and 10 (5.43 lM). Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction The success of Cisplatin as an anti-cancer drug stimulated research in finding new metal-complexes that are less toxic, more efficient and active against a number of diseases. Over the past 5 decades, a number of metal complexes with anti-bacterial [1,2], anti-fungal [3,4], anti-malarial [5,6] and anti-cancer [7–10] proper- ties, have been developed. Transition metals coordinated with nitrogen donor ligands, account for the majority of known active metal complexes. Schiff base ligands have been widely used as coordinating ligands to transition and main group metals [11,12]. Most recently, metal complexes containing pyrrole Schiff base ligands have been shown to possess a wide spectrum of biological activities which include anti-cancer and anti-microbial [12–14]. We recently reported the synthesis of pyrrole. Schiff base sulfonamide ligand, via the reaction of magnesiated pyrrole and benzonitrile [15]. The ligand is a potential bi-dentate ligand to a number of transition metals. Sulfonamides and their derivatives have received much attention due to their excellent activity against bacterial diseases, low toxicity and relatively low cost [16]. A number of sulfonamide metal complexes have been shown to possess catalytic activity [17] and good to excellent bio- logical activities [16–22]. In this paper, we report the complexation of a new pyrrole Schiff base sulfonamide ligand with Cu, Ni, Zn, Ag, Pt and Co, and their anti-cancer properties. 2. Experimental 2.1. Materials and methods Metal salts, organic chemicals such as 1,8-Diazabicyclo[5.4.0] undec-7-ene (DBU), cyclooctadiene (COD), and solvents were com- mercially available (Aldrich and Fluka) in high purity and used as received. 1 H and 13 C NMR spectra were recorded at 300.139 MHz and 75.035 MHz, respectively, on Bruker Avance-300 spectrometer. Infrared spectra were obtained on Bruker Tensor 27 spectrometer. Samples were placed on a diamond tip. The absorptions are reported on the wavenumber (cm 1 ) scale, in the range 400–4000 cm 1 . High-resolution, low-resolution and fast atom bombardment (FAB) mass spectra were recorded on a VG70-SEQ http://dx.doi.org/10.1016/j.poly.2017.03.051 0277-5387/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Fax: +27 015 268 2432. E-mail address: Winston.nxumalo@ul.ac.za (W. Nxumalo). Polyhedron 129 (2017) 240–245 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly