Papers by Fezile Siphiwe Wiseman Potwana
The aim of the study was the synthesis and characterization of new mixed ligand saccharinato comp... more The aim of the study was the synthesis and characterization of new mixed ligand saccharinato complexes of various groups 9, 10, 11 and 12 metals, i.e. M = Cd(II), Co(II), Zn(II), Hg(II), Cu(II), and Ni(II) using dimethyl sulfoxide (DMSO) and amine-based ligands such as ethylenediamine (en), N-methyldiethanolamine (MDEA) and 2-(methylamino)ethanol (MEA) from the precursor [M(C 7 H 5 SO 3 N) 2 (H 2 O) 4 ]•2H 2 O. The new complexes were characterized by elemental analyses, solution Nuclear Magnetic Resonance (NMR), UV-Vis spectroscopy, IR ATR spectroscopy, thermal analysis and single crystal X-ray diffraction. All complexes are mononuclear except complex (9) which is a dinuclear Cu(II) complex. A number of the saccharinato complexes are diamagnetic, i.e. trans-[Cd(sac) 2 (dmso) 2 (H 2 O) 2 ] (1), cis-[Zn(sac) 2 (dmso) 2 ] (3), [Hg(sac) 2 (dmso)(H 2 O)] (4) and trans-[Cd(sac) 2 (en) 2 ] (11) and were characterised by NMR. Some of the complexes are paramagnetic, including trans-[Co(sac) 2 (dmso) 2 (H 2 O) 2 ] (2), [Cu(sac) 2 (dmso)(H 2 O) 2 ] (5), [Cu(sac) 2 (N,O,O-mdea) 2 ] (7), [Co(sac) 2 (N,O,O-mdea) 2 ] (8) and [Ni(sac) 2 (en) 2 ] (10). All complexes containing the DMSO ligand were successfully analysed by single crystal X-ray diffraction, i.e. complexes (1) to (5). The complexes crystallized in the monoclinic P21/c space group together with complex (11). Complexes [Ni(N,O,O-mdea)]•2(sac) (6), [Cu 2 (µ-O) 2 (mea) 4 ]•2(sac) (9), and [Co 2 (en) 4 (CO 3) 2 ]•2(sac)3H 2 O (12) were found to crystallize in the triclinic P-1 space group. In DMSO complexes, the metal ion is positioned at the centre of symmetry and complexes (1) and (2) are octahedrally coordinated by two monodentate DMSO ligands which are trans to each other and two aqua-ligands which are also trans to each other. The ligands in complex (3) are tetrahedrally coordinated to the Zn(II) ion in the cis position and in complex (4) a distorted trigonal bipyramidal complex was found whereby the DMSO groups are disordered over two places and the site occupancy factors were refined to 0.504(4) and 0.496(4), respectively. Complex (5) consisted of Cu(II) ions in a trigonal bipyramidal geometry. Complexes (6) and (12) have an octahedral coordination geometry with the metal ion positioned at the centre of symmetry. Complex (9) is a centrosymmetric binuclear complex containing two strongly distorted square-pyramidal coordinated copper(II) ions bound together by two alkoxo bridges. The bridging oxygen is a deprotonated oxygen of the ethanolic group of MDEA. The MDEA ligand also coordinates to the copper(II) ions through its nitrogen, while the other ethanolic group is not involved in the coordination. For complexes (6), (9) and (12) the saccharin acts as a weak counter ion and complex (12) has a v lattice containing three water molecules of crystallization held together by a hydrogenbonded network. xi
Acta Crystallographica Section E Structure Reports Online, 2011
Acta Crystallographica Section E Structure Reports Online, 2011
Bis(dimethyl sulfoxide-κO)bis(saccharinato-κN)zinc(II) Fezile S. W. Potwana, Bongakonke E. Shandu... more Bis(dimethyl sulfoxide-κO)bis(saccharinato-κN)zinc(II) Fezile S. W. Potwana, Bongakonke E. Shandu and Werner E. Van Zyl S1. Comment Saccharin (o-sulfobenzimide; 1,2-benzothiazole-3(2H)-one 1,1-dioxide; Hsac) is a widely used artificial sweetening agent. The imino hydrogen is acidic and can be readily deprotonated. The coordination chemistry of this anion is versatile due to the different coordination sites to metallic centers it can accommodate, i.e., one N, one O (carbonylic) and two O (sulfonic) atoms. These donor atoms of the anion can thus readily generate either Nor O-monodentate or bidentate (N, O) coordination. Saccharin is normally used as the sodium or calcium salt which dramatically improves water solubility. Most metal complexes contain the deprotonated form of saccharin, and this saccharinate anion (sac) is commercially available as the sodium salt, used in the present study. The reaction of sodium saccharinate with a variety of divalent transition metal ions results in coordination complexes with general formula [M(sac) 2 (H 2 O) 4 ].2H 2 O, (M = V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd), which all show a clear preference to bind through the deprotonated anionic N-atom (Baran and Yilmaz, 2006). These octahedral complexes contain two N-bonded sac ligands in trans positions, and complexes of the type [M(sac) 2 (H 2 O) 4 ].2H 2 O are thus commonly used as precursors in the synthesis of mixed-ligand saccharinate supporting information sup-6
Acta Crystallographica Section E Structure Reports Online, 2011
The title compound, [Cd(C 7 H 4 NO 3 S) 2 (C 2 H 6 OS) 2 (H 2 O) 2 ], contains a Cd 2+ cation in ... more The title compound, [Cd(C 7 H 4 NO 3 S) 2 (C 2 H 6 OS) 2 (H 2 O) 2 ], contains a Cd 2+ cation in an octahedral coordination environment. The metal atom is surrounded by the two different neutral ligands dimethyl sulfoxide (DMSO) and water, each coordinating through the O atom. The anionic saccharinate (sac; 1,1,3-trioxo-2,3-dihydro-1 6 ,2-benzothiazol-2-ide) ligand coordinates through the N atom. Each of the three similar ligand pairs is in a trans configuration with respect to each other. The Cd atom lies on a crystallographic center of symmetry. The DMSO ligand coordinates through the lone pair of electrons on the O atom, as can be seen from the Cd-O-S bond angle of 123.96 (9) .
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Papers by Fezile Siphiwe Wiseman Potwana