Eric S. Raper

Complexes of heterocyclic thione donors

Major ligand abbreviations 116 A. Introduction 116 B. General aspects of heterocyclic thione donors 117 C. Complexes of nitrogen containing heterocyclic thiones 121 (i) Pyrrolidine-thiones 121 (ii) 1,3-Imidazoline-2-thiones 121 (iii) Triazoline-thiones 134 (iv) Tetrazoline-thiones 137 (v) Piperidine-thiones 139 (vi) Thiomorpholine-3-thione 141 (vii) c-Thiocaprolactam 142 (viii) Pyridine-thiones 143 (ix) Pyrimidine-thiones 145 (x) Thiouracils and thiocytosines 150 (xi) Purine-thiones 153 (xii) Pyridazine-thiones 154 (xiii) 1,3,5-Triazine-2,4,6-trithione 155 (xiv) Quinoline-8-thione 155 (xv) Quinoxazoline-di-thione 155 D. Complexes of nitrogen and sulphur containing heterocyclic thiones 156 (i) Thiazoline-thiones 156 (ii) Benzo-1,3-thiazoline-2-thione 156 (iii) 1,3-Thiazolidine-2-thione 161 (iv) 1,3-Thiazolidine-2-thione-5-one 165 (v) 1,2,4-Dithiazoline-3-amino-5-thione 166 (vi) 1,3,4-Thiadiazoline-thiones 167 E. Complexes of nitrogen and oxygen containing heterocyclic thiones 171 (i) 1,3-Oxazolidine-2-thione 171 (ii) Benz-1,3-oxazoline-2-thione 171 (iii) 1,3,4-Oxadiazoline-2-thione 174 F. Complexes of sulphur containing heterocyclic thiones 174 G. Final comments 175 Acknowledgements 176 References 176

COMPLEXES OF HETEROCYCLIC THIONATES. PART 1. COMPLEXES OF MONODENTATE AND CHELATING LIGANDS

Abstract The monodentate and chelating behaviour of deprotonated heterocyclic thiones, otherwise known as the heterocyclic thionates, with transition and other metals is reported. The range of ligands involved is large and includes pyrimidine, imidazole, triazole, quinoline, purine, thiazole, thiadiazole and oxazole molecules, mostly as their monothionate derivatives. Some dithionate derivatives of mostly pyrimidine, quinoxaline and thiadiazole are also included. The preparation, spectroscopy and, in some cases, the electrochemical properties of the complexes are described. The review emphasizes the resultant geometries and dimensions derived from the crystal structures of the complexes contained in almost 180 references. Heterocyclic thionates are ambidentate monodentate ligands. They are sulphur donating towards organ omercury(11) and aurophosphine(1) cations with supplementary intramolecular attachments to the thioamido nitrogen atoms in many cases. The alternative monodentate nitrogen-donating behaviour is mostly limited to zinc(II) complexes of benzo-1,3-thiazoline2-thionate. Monosubstituted heterocyclic thionates are S,N-chelating and mostly generate four-membered rings. Some quinoline thionate derivatives are also S,N-chelating and generate five-membered rings. The dithionate derivatives are generally S,S-chelating and also generate five-membered rings. The complexes are mostly mononuclear with coordination at the metal ranging from two, for monodentate ligands, to eight for tetrachelates. The effect of deprotonation and coordination on the dimensions of parent heterocyclic thiones, especially those of pyridine-2-thione and benzo-1,3-thiazoline-2-thione, are also reported and discussed.

Complexes of heterocyclic thionates Part 2: complexes of bridging ligands

The bridging behaviour of deprotonated heterocyclic thiones, the heterocyclic thionates, is reported. The anions are effective bridging ligands among binuclear, trinuclear, tetranuclear hexanuclear and polynuclear metallic species. The metals involved are mostly from the second and third series of transition metals together with some from the first transition series. Some examples involving main group metals are also included. The anionic ligands included in the review mostly involve the monothionate derivatives of pyridine, imidazole, triazole, quinoline, thiazole, and thiadiazole derivatives. Dithionate derivatives are few in number and are limited to μ2-S,N bridging pyrimidine and μ2-S,S bridging 1,2,5-thiadiazole bases. Several bridging modes are described. These may involve the exclusive use of the thionate sulphur atom in the rare edge-bridging, μ2-S(η2-S), of two metal centres. Alternatively, both the sulphur and the nitrogen atoms of the thioamide groups may be involved in the formation of either binuclear double-bridging, μ2-(η1-S;η1-N), or binuclear triple-bridgng, μ2-(η2-S;η1-N) systems. Trinuclear face-briding, μ3-(η2-S;η1-N), ligands occur among trinuclear, tetranuclear and octahedral complexes. Relatively rare tetranuclear, μ4 (η3-S;η1-N), bridging ligands generate polymeric and oligomeric complexes. Combinations of similar, or different, bridging arrangements are also involved in the formation of double or multiple bridges among binuclear and polynuclear metal centres. Preparative routes, vibrational and electronic spectra as well as the electrochemistry of the complexes are described and discussed. Isomeric forms of the complexes, arising mostly from a combination of the bifunctional and polydentate character of the bridging ligands towards the metal centres, are also described and discussed. The review emphasises the structures and dimensions derived from the X-ray crystallographic study of a large number of binuclear and polynuclear complexes. The effect of deprotonation and coordination on the dimensions of some of the parent ligands is also reported and discussed. Some structures, as well as some structural changes, derived from solution NMR spectra, are also reported.

Copper complexes of heterocyclic thioamides and related ligands

Abstract The review covers copper complexes of thiazoles, thiadiazoles, thioamides, thiones and imidazole-, thiazole-, pyridine- and quinazoline-thionates. Synthetic and, spectroscopic data are presented but emphasis is placed on detailed discussion of the structural aspects of these species based upon X-ray data.

Copper(I) halide complexes of imidazole thiones: Crystal structure of dimeric monochloro bis(1-methylimidazoline-2-thione) copper(I)

Abstract Copper(I) halides form complexes with imidazole-2-thione imtH2, 1-methylimidazoline-2-thione, imtH and 1,3-dimethylimidazoline-2-thione, dmimt of formula: Cu(imtH2)X (X = Cl, Br, I) and CuL2X (L = mimtH and dmimt; X = Cl, Br, I). These complexes have been characterised by a variety of physical and spectroscopic techniques. The crystal structure of Cu(mimtH)2Cl consists of centrosymmetrically constrained dimers occupying a monoclinic unit cell of space group P21/n with Z = 2. The dimers contain a pair of copper(I) atoms tetrahedrally coordinated by terminal chlorine and terminal S-bonded mimtH together with two S-bridging (μ2) mimtH molecules. The Cu2S2 core of the dimer is lozenge shaped with CuS distances of 2.301(1) and 2.572(1) A, a CuSCu angle of 73.2(1)° and separation distances of 2.914(1) and 3.916(1) A between copper atoms and sulphur atoms, respectively. The final R index for 1937 counter reflections is 0.0308.

tetrahedro-[Tetrakis {(1-methylimidazoline- 2(3H) -thionato) copper(I)}]: electrochemical synthesis, thermal analysis, cyclic voltammetry and crystal structure

Abstract The complex, [{Cu(mimt)} 4 ], has been electrochemically synthesised in acetonitrile using a copper anode, a platinum cathode and the parent ligand, 1-methylimidazoline-2(3 H )-thione (mimtH), with tetrabutylammonium tetrafluoroborate as supporting electrolyte. The colourless diamagnetic complex crystallises in a tetragonal cell, a = b =10.1002(6), c =11.6861(8) A, V =1192.2(1) A 3 , Z =2(tetramers), space group P 4 2 / n , final conventional R =0.043, from 721 observed reflections with F >4σ c ( F ). The tetranuclear complex possesses a crystallographically imposed four-fold inversion axis ( 4 ) and a slightly flattened Cu 4 tetrahedron with CuCu distances of 2.671(2) A, along four of the edges, and 3.132(2) A along the remaining two opposing edges of the tetrahedron; internal, CuCuCu angles, between the shorter CuCu distances, are 71.8(1)°. The deprotonated ligands form μ 2 -S, N bridges with three copper(I) atoms on each of the isosceles triangular faces of the Cu 4 tetrahedron. The exocyclic thionato-S atom bridges two copper(I) atoms (CuS br =2.307(2) and 2.233(2) A) and the hetero-N atom bonds to a third metal atom (CuN=1.995(6) A). Consequently, each copper(I) atom has a S 2 N-donor set and irregular, trigonal-planar coordination with angles at the metal ranging from 109.3(2)–129.9(1)°. The complex exhibits ligand centred, irreversible redox behaviour in acetonitrile and is stable to aerial oxidation at room temperature. Thermal degradation to the metal occurs in flowing air (275–750 °C) with endothermic decomposition in flowing dinitrogen.

Tris-(1-methylimidazoline-2(3H)-thione)copper(I) nitrate: Preparation, thermal analysis and crystal structure

Abstract The preparation of a complex of 1-methylimidazoline-2(3H)-thione) (mimtH) with copper(II) nitrate is described. A combination of elemental and thermal analysis has shown the formula to be, Cu(mimtH)3(NO3). Magnetic measurements, infrared spectroscopy and a single crystal X-ray study have established the presence of copper(I) in distorted trigonal planar, Cu(mimtH)3+, cations. Averaged dimensions within the coordination sphere are: 2.249(A) (CuS), 119.6° (SCuS) and 107.3° (CuSC). The nitrate ions form hydrogen bonds (NH O) with the imido groups of the ligands.

Complexes of imidazoline (1,3H)-2-thione with Co(II) and Zn(II) salts

Abstract Complexes of imidazoline-2(1,3H)-thione (ImT,L), have been prepared with Co(II) and Zn(II) salts. Stoichiometries of the complexes, ML2X2, for the halides and ML4X2 for the nitrates and perchlorates, have been established by chemical analysis. Thermal analysis has revealed the extent of hydration among the cobalt complexes. The solid complexes have been further characterised by means of magnetic susceptibility data, infrared and visible spectral measurements. The soluble complexes have been studied by means of electrolytic conductance measurements and their visible spectra have also been recorded. Ligand field parameters have been determined and probable structures assigned. The ligand coordinated by means of its exocyclic sulphur atom and one of its ring nitrogen atoms in the solid complexes. For the soluble complexes coordination involves the sulphur atom only.

trans-Bis[(thiocyanato-S)(1-methylimidazoline-2(3H)-thione)-μ2-(1-methylimidazoline-2(3H)-thione)copper(I)]: preparation, thermal analysis and crystal structure

Abstract 1-Methylimidazoline-2(3 H )-thione (mimtH) and copper(I) thiocyanate in refluxing ethanolacetonitrile produce a colourless, diamagnetic complex, [Cu 2 (mimtH) 4 (SCN) 2 ], which crystallises in an orthorhombic cell ( a =8.0724(3), b =15.9545(6), c =21.3357(8) A), space group= Pbca , Z =4, final R =0.0319 from 2427 observed reflections F >4σ c (F)). In the dimeric complex the copper(I) atoms are pseudo-tetrahedrally coordinated by pairs of, respectively, asymmetrically μ 2 -S bridging mimtH, terminal monodentate-S mimtH, (CuS=2.290(1) A), and terminal monodentate-S thiocyanate, (CuS=2.332(1) A). Each pair of ligands is trans -related to its partner across crystallographic centres of symmetry, consequently, each copper(I) atom has an identical S 4 donor set with angles at the metal ranging from 95.9(1)° to 121.8(1)°. The centro-symmetric Cu 2 S 2 core is rhomboid with CuS=2.377(1) and 2.457(1) A, CuS br Cu=72.6(1)° and CuCu, S br S br separation distances of 2.861(1) and 3.897(2) A, respectively. Thermal decomposition of the complex in flowing air, (133–1000 °C), involves de-sulfurisation of mimtH and thiocyanate with concomitant production of copper(II) sulfide followed by oxidation to copper(II) oxide.

Complexes of heterocyclic thiones and Group 12 metals: Part four. Preparation and characterisation of 1:1 complexes of mercury(II) halides with 1,3-thiazolidine-2-thione and 1,3-benzothiazoline-2-thione. Crystal structure of the discrete trans dimer [(μ-dibromo)bis(trans{(bromo)(1,3-thiazolidine-2-thione)}mercury(II))]

Abstract The addition of 1,3-thiazolidine-2-thione (tzdSH) or 1,3-benzothiazoline-2-thione (bztzSH) to mercury(II) halides in equimolar quantities in ethanolic solutions resulted in the formation of the 1:1 complexes LHgX2 (L=tzdSH, bztzSH; X=Cl, Br, I) which were characterised by elemental analysis. Spectroscopic evidence confirmed the exocyclic sulphur to be the donor atom in the thione form of the ligand and that the complexes were halogen bridged dimers. The X-ray structure of [(tzdSH)HgBr2]2 shows the molecule to be a centrosymmetric double halogen bridged dimer with distorted tetrahedral coordination geometry for Hg; secondary Hg⋯Br interactions link the molecules together into chains, and there are intramolecular N–H⋯Br hydrogen bonds between the heterocyclic ligands and the bridging bromides.