Synthesis, structure and reactivity with phosphines of Hg(II) ortho -cyano-aminothiophenolate complexes formed via C-S bond cleavage and dehydrogenation of 2-aminobenzothiazoles

• Published in: Dalton transactions : an international journal of inorganic chemistry 2022-05, Vol.51 (20), p.7889-7898
• Main Authors: Al-Jibori, Subhi A, Irzoqi, Ahmed A, Al-Janabi, Ahmed S M, Al-Nassiry, Amenah I A, Basak-Modi, Sucharita, Ghosh, Shishir, Wagner, Christoph, Hogarth, Graeme
• Format: Article
• Language: English
• Subjects: Aminobenzothiazoles; Binding; Chelates; Cleavage; Coordination polymers; Crystallography; Dehydrogenation; Ligands; Low temperature; Mercury (metal); Mercury compounds; Molecular structure; Nitrogen dioxide; Perturbation; Phosphines; Ring opening; Substitutes
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d2dt00391k

Addition of 2-aminobenzothiazole (abt) and substituted derivatives to Hg(OAc) leads to the high yield formation of -cyano-aminothiophenolate (ocap) complexes [Hg{SC H XN(CN)}] (X = H, Me, Cl, Br, NO ) resulting from dehydrogenation and C-S bond cleavage. The reaction appears to be unique to Hg(OAc) and with HgCl the product [HgCl (abt)] contains an intact abt ligand, but reacts with acetate to afford the ocap complex [Hg{SC H N(CN)}] . Binding of abt to Hg(II) has previously been probed in molecular structures of [Hg(sac) (abt)L] (L = MeOH, DMSO) and these have been reexamined to understand the perturbation of abt upon coordination. When the reaction of abt and Hg(OAc) was carried out at low temperatures the intermediate [Hg(κ -OAc)(EtOH)(μ-HNCNSC H )] was isolated resulting from a single ligand deprotonation thus allowing a mechanism for ring-opening to be proposed. Reactions of [Hg{SC H XN(CN)}] with mono- and bidentate phosphines have been studied, affording a series of complexes in which the ocap ligands adopt four different binding modes in the solid state, as shown by a number of crystallographic studies. In all, the ligand chelates to a single mercury centre but spans to the second either: (i) a simple S,N-chelate, (ii) coordination through nitrogen of the CN group, (iii) the sulfur acting as a thiolate-bridge, (iv) both thiolate bridging and cyanide coordination. With PPh two different binding modes are seen in complexes [Hg{SC H XN(CN)}(PPh )] being dependant upon the nature of the arene-substituent, while addition of excess PPh affords mononuclear [Hg{SC H XN(CN)}(PPh ) ]. With dppm, binuclear [Hg{SC H XN(CN)}(κ -dppm)] result in which the diphosphine binds in a monodentate fashion. With the more flexible diphosphines, dppe and dppb, coordination polymers [Hg{SC H XN(CN)}(κ ,κ -diphosphine)] result in which ocap binds in a simple chelate fashion. Somewhat unexpectedly, with dppp, binuclear complexes [Hg {SC H XN(CN)} (μ,κ ,κ -dppp)] result in which two diphosphines bridge the Hg centre, while with dppf mononuclear chelates are proposed to result. Thus, the simple and high-yielding ring-opening of 2-aminobenzothiazole and substituted derivatives by mercuric acetate provides ready access to a range of novel -cyano-aminothiophenolate complexes, being shown to be a highly versatile ligand that can adopt a number of different coordination modes.