Authors: Subhi A. Al‐Jibori | Ahmed A. Irzoqi | Ahmed S. Al‐Janabi | Amenah I. A. Al‐Nassiry | Sucharita Basak-Modi | Shishir Ghosh | Christoph Wagner | Graeme Hogarth
Source: Dalton Transactions (article, 2022-01-01)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Synthesis, structure and reactivity with phosphines of Hg(<scp>ii</scp>)<i>ortho</i>-cyano-aminothiophenolate complexes formed<i>via</i>C–S bond cleavage and dehydrogenation of 2-aminobenzothiazoles Addition of 2-aminobenzothiazole (abt) and substituted derivatives to Hg(OAc)<sub>2</sub> leads to the high yield formation of <i>ortho</i>-cyano-aminothiophenolate (ocap) complexes [Hg{SC<sub>6</sub>H<sub>3</sub>XN(CN)}]<sub><i>n</i></sub> (X = H, Me, Cl, Br, NO<sub>2</sub>) resulting from dehydrogenation and C-S bond cleavage. The reaction appears to be unique to Hg(OAc)<sub>2</sub> and with HgCl<sub>2</sub> the product [HgCl<sub>2</sub>(abt)]<sub><i>n</i></sub> contains an intact abt ligand, but reacts with acetate to afford the ocap complex [Hg{SC<sub>6</sub>H<sub>4</sub>N(CN)}]<sub><i>n</i></sub>. Binding of abt to Hg(II) has previously been probed in molecular structures of [Hg(sac)<sub>2</sub>(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)<sub>2</sub> was carried out at low temperatures the intermediate [Hg(κ<sup>2</sup>-OAc)(EtOH)(μ-HNCNSC<sub>6</sub>H<sub>4</sub>)]<sub>2</sub> was isolated resulting from a single ligand deprotonation thus allowing a mechanism for ring-opening to be proposed. Reactions of [Hg{SC<sub>6</sub>H<sub>3</sub>XN(CN)}]<sub><i>n</i></sub> 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 <i>via</i> 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<sub>3</sub> two different binding modes are seen in complexes [Hg{SC<sub>6</sub>H<sub>3</sub>XN(CN)}(PPh<sub>3</sub>)]<sub>2</sub> being dependant upon the nature of the arene-substituent, while addition of excess PPh<sub>3</sub> affords mononuclear [Hg{SC<sub>6</sub>H<sub>3</sub>XN(CN)}(PPh<sub>3</sub>)<sub>2</sub>]. With dppm, binuclear [Hg{SC<sub>6</sub>H<sub>3</sub>XN(CN)}(κ<sup>1</sup>-dppm)]<sub>2</sub> result in which the diphosphine binds in a monodentate fashion. With the more flexible diphosphines, dppe and dppb, coordination polymers [Hg{SC<sub>6</sub>H<sub>3</sub>XN(CN)}(κ<sup>1</sup>,κ<sup>1</sup>-diphosphine)]<sub><i>n</i></sub> result in which ocap binds in a simple chelate fashion. Somewhat unexpectedly, with dppp, binuclear complexes [Hg<sub>2</sub>{SC<sub>6</sub>H<sub>3</sub>XN(CN)}<sub>2</sub>(μ,κ<sup>1</sup>,κ<sup>1</sup>-dppp)] result in which two diphosphines bridge the Hg<sub>2</sub> 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 <i>ortho</i>-cyano-aminothiophenolate complexes, being shown to be a highly versatile ligand that can adopt a number of different coordination modes. Dehydrogenation ; Cleavage (geology) ; Chemistry ; Bond cleavage ; Reactivity (psychology) ; Medicinal chemistry ; Stereochemistry ; Organic chemistry ; Catalysis ; Materials science Organic and Molecular Conductors Research ; Magnetism in coordination complexes ; N-Heterocyclic Carbenes in Organic and Inorganic Chemistry