James R. Creighton

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.

Complexes of heterocyclic thiones and group twelve metals Part 1. Preparation and characterisation of 1:1 complexes of mercury(II) halides with 1-methylimidazoline-2(3H)-thione: the crystal structure of [(μ2-dibromo) bis(trans{(bromo) (1-methyl-imidazoline-2(3H)-thione)}mercury(II))] at 160 K

Abstract Stoichiometric (1:1) addition of aqueous alcoholic solutions of 1-methylimidazoline-2(3H)-thione (meimz2SH) to a similar series of mercury(II) halides produced crystalline complexes of empirical formula [HgX 2 (meimz2SH)] (X = Cl, Br, l). The chemical formulae of the complexes have been characterised by elemental chemical analysis. IR and 11 C NMR spectra indicated the presence of the thione form of the heterocyclic ligands in the complexes, as well as their thione-sulphur ligating character. The crystal structure of [HgBr 2 (meinz2SH)] 2 ] has been determined by single crystal X-ray diffraction methods. The complex crystallises in a monoclinic unit cell with a = 7.7063(13), b = 14.471(3), c = 25.705(4) A , β = 95.114(9)°, Z = 6 (dimers) and space group P 2 1 / n . The asymmetric unit consists of one general dimeric complex and half of a dimeric molecule on an inversion centre. Weak intermolecular secondary contacts occur between terminal bromine and mercury(II) atoms (Hg⋙Br=3.587−3.791 A). These contacts link the bromo-bridged dimers into weakly associated polymeric sheets, Consequently, the mercury(II) atoms have distorted trigonal-bipyramidal coordination in this complex. The apical sites of the trigonal-bipyramidal polyhedra are occupied by terminal bromine (HgBr terminal = 2.489(2)−2.532(2) A) and terminal thione-sulphur (HgS = 2.405(4) − 2.419(4) A) atoms. Equatorial bromine atoms consist of the long intermolecular bromine contacts and the bridging bromine atoms (HgBr bridging = 2.659(2) − 2.859(3) A). The latter arre also involved in the central, binuclear asymmetric Hg 2 (μ-Br) 2 cores. These cores also contain long Hg⋙Hg′ contacts (3.901 and 4.041 A) and narrow bridgingangles (HgBrHg = 89.90(5)−90.62(5)°). Further intermolecular contacts between the ligand amide (NH) groups and some of the bridging and terminal bromine atoms (NH…Br = 2.555−2.683 A) generate an extensive H-bonded network.

Tetrakis(1-methylimidazoline-2-thione)-μ2-bis(1-methylimidazoline-2-thione)-di-copper(I) tetrafluoroborate: Preparation, thermal analysis and crystal structure

Abstract Reaction between copper(II) tetrafluoroborate and 1-methylimidazoline-2-thione (mimtH) in acetone-acetonitrile solution and a dinitrogen atmosphere produced a compound of empirical formula, Cu(mimtH)3(BF4), which has been characterised by a variety of physical techniques. The crystal structure of the compound contains centrosymmetrically constrained dimeric cations, [Cu2(mimtH)6]2+, in a monoclinic unit cell (a= 14.499(1), b=16.195(2), c=8.433(1) A, β=93.377(8)°, space group P21/c and Z=2), together with disordered tetrafluoroborate anions. The dimeric cations contain a pair of copper(I) atoms tetrahedrally coordinated by a pair of terminal S-bonded mimtH molecules (CuS (averaged)=2.328 A) and a pair of asymmetrically S-bridging (μ2) mimtH molecules. The Cu2S2 core of the dimer is lozenge shaped with CuS distances of 2.358(1) and 2.459(1) A, and a CuSCu angle of 77.2°. Distances of 3.003 and 3.766 A separate the copper atoms and the sulphur atoms within the Cu2S2 core, respectively. The final R index for 3786 observed reflections is 0.0497. Thermal decomposition of the complex in air (145–1000 °C), involves evolution of mimtH, desulphurisation of mimtH and copper(I,II) sulphide production followed by conversion of the mixed sulphides to copper(II) oxide.

Complexes of heterocyclic thiones and Group 12 metals: Part 3. Preparation and characterisation of 1:2 complexes of mercury(II) halides with 1-methylimidazoline-2(3H)-thione: the crystal structures of [(HgX2)(1-methylimidazoline-2(3H)-thione)2] (X=Cl, Br, I) at 160 K

Abstract The stoichiometric addition (1:2 metal–ligand) of aqueous alcoholic solutions of the metal salts to similar solutions of 1-methyl-imidazoline-2(3 H )-thione (1-meimz2SH) generated crystalline complexes of general formula, [HgX 2 (1-meimz2SH) 2 ] (X=Cl, Br, I), in good yield. The chemical formulae of the complexes have been characterised by elemental chemical analysis. Infrared and 13 C NMR spectra indicated the presence of the thione form of the heterocyclic ligands in the complexes, as well as their thione–sulfur ligating character. X-ray crystal structure analyses have been performed on the three complexes. The metal in the chloro complex occupies a crystallographic two-fold axis which bisects the SHgS angle. The bromo and iodo complexes occupy general positions, but one of the ligands is disordered in the bromo complex. All of the complexes are mononuclear with the four-coordinate metals possessing distorted tetrahedral geometry. The extent of the distortion is indicated by the angles at the metal which range from 93.71(7) to 127.73(7)°. Metal–sulfur distances range from 2.4514(14) to 2.571(3) A. Metal–halogen distances range from 2.5984(13) A (chloro) through 2.641(3) and 2.647(3) A (bromo) to 2.7866(11) and 2.8047(9) A (iodo). Hydrogen bonds, involving the thioamide hydrogen (NH) and halogen atoms are exclusively intramolecular in the chloro complex, but both intramolecular and intermolecular in the bromo and iodo complexes.

Preparation, characterisation and crystal structure of dichloro tetrakis-(1-methylimidazoline-2(3H)-thione)palladium(II) dihydrate

Abstract The preparation of a complex of 1-methylimidazoline-2(3H)-thione (MImt) with palladium dichloride in acid solution is described. The stoichiometry, Pd(MImt)4Cl2·2H2O has been established by chemical and thermal analysis. The compound has been characterised by means of infrared spectroscopy and a single crystal X-ray study. The latter has confirmed the presence of uncoordinated water molecules, ionic chloride ions and square-planar [PdS4]2+ units bridged by H-bonds.

Complexes of heterocyclic thiones and Group 12 metals: Part 2: The chemical and electrochemical synthesis of mercury(II) complexes of 1-methylimidazoline-2(3H)-thionate. The crystal structure of trans-[bis-{(η1-S-1-methylimidazoline-2(3H)-thione)(η1-S-1-methylimidazoline-2(3H)-thionate)(μ2-S,N-1-methylimidazoline-2-thionate)mercury(II)}] at 160 K

Abstract Two complexes of mercury(II) and the anion of 1-methylimidazoline-2(3H)-thione (1-meimz2SH) have been prepared and characterised. The addition of an aqueous solution of mercury(II) acetate to an aqueous solution of 1-methylimidazoline-2(3H)-thione and triethylamine produced [Hg(1-meimz2S)2], as a colourless and intractable precipitate. The electrochemical oxidation of elemental mercury, in the presence of a saturated acetonitrile solution of 1-methylimidazoline-2(3H)-thione and a supporting electrolyte, produced two crystalline products, a pale-yellow microcrystalline complex, [Hg(1-meimz2S)2] and a colourless crystalline complex, [Hg(1-meimz2S)2(1-meimz2SH)]. An X-ray crystal structure analysis of [Hg(1-meimz2S)2(1-meimz2SH)] showed that the complex consists of discrete, centrosymmetrically constrained, mercury(II) dimers. Each dimer contains a pair of bifunctional, binuclear bridging, μ2-S,N(η1-S;η1-N), 1-methylimidazoline-2(3H)-thionate anionic ligands (HgSbridging=2.5196(6), HgN=2.325(2) A, NCSexo=126.0(2)°). The bridging ligands adopt a ‘head-to-tail’ configuration. This arrangement generates a central eight-membered ring, Hg2S2C2N2, in the complex. The ring adopts a chair conformation. Distorted, pseudo-tetrahedral four-coordination at each metal is completed by a pair of monodentate, sulfur donating, 1-methyl-imidazoline-2(3H)-thione neutral and anionic ligands (HgSthione=2.5735(7) and HgSthionate=2.4829(7) A). NH ⋯ N hydrogen bonds (N ⋯ N=2.701 A) effectively link the terminal ligands into eight-membered chelates.

Polymeric cyano(1-methylimidazoline-2-thione)copper(I), [Cu(mimtH)CN]n: preparation, spectroscopy, thermal analysis and crystal structure

The addition of 1-methylimidazoline-2-thione (mimtH) to a solution of CuCN in aqueous (0.1 M) KCN produced a colourless crystalline solid of empirical composition Cu(mimtH)CN. The compound crystallises in a monoclinic unit cell a =7.6042(4) b =7.2155(4) c =13.6004(4) A, β=98.233(6)° space group Pc and Z =2. The cyano groups bridge pairs of copper( I ) atoms in a virtually linear manner (CuCN(mean) 175.0°; CuNC(mean) 175.3°; Cu…Cu 5.027 A). Pairs of mimtH ligands asymmetrically bridge pairs of copper( I ) atoms with the production of essentially planar Cu 2 S 2 cores (CuS(mean), 2.355 and 2.561 A; CuSCu(mean) 79.4°; Cu…Cu 3.145 A; S…S 3.729 A). Each copper atom is tetrahedrally coordinated by a S 2 CN donor set with angles at the metal ranging from 98.4(1) to 120.2(1)°. The effective structural unit consists of six copper( I ) atoms, four cyano and four mimtH ligands, extended into a two-dimensional polymeric array. The copper atoms and the cyano groups form the essentially planar component of the polymer which extends along the b and c axes of the unit cell with the a axis representing the separation distance between adjacent planar layers. The μ 2 -S bridging ligands occupy space on both sides of the planar section of the polymer. Final conventional R =0.0275 for 2493 observed data (F>4 σ(F)). The compound is diamagnetic and appears to be indefinitely stable to aerial oxidation at room temperature. An absorption band at 190 cm −1 in the Raman spectrum is tentatively assigned to a bridging stretching frequency, v (CuSCu). The compound thermally decomposes to Cu(II)O in air in the temperature range 145 to 800 °C and involves desulphurisation of mimtH ligands cyanogen evolution production of Cu(II)S and conversion of the latter to Cu(II)O.

Bis(imidazolidine-2-thione)(thiocyanato-N)copper(I): preparation, thermal analysis and crystal structure

Abstract Reaction between copper(I) thiocyanate and imidazolidine-2-thione (imdtH 2 ) in ethanol-acetonitrile solution produced a compound of formula [Cu(imdtH 2 ) 2 (NCS)], which has been characterised by a combination of spectroscopic thermal and crystal structure analysis. [p ]The crystal structure of the compound consists of neutral mononuclear molecules in which the central metal and the thiocyanate atoms occupy crystallographic mirror planes in the monoclinic unit cell ( a =6.081(3) b =14.583(7) c =7.351(2) A, β=103.46(4)° space group P 2 1 / m , Z =2). The complex contains a CuS 2 N arrangement formed from two monodentate S-donating imdtH 2 ligands (CuS=2.221(1) A) and an N-donating thiocyanate anion (CuN=1.956(4) A). Angles at the Cu(I) atom (119.2(1); 121.6(1)°) are consistent with a relatively undistorted trigonal arrangement at the metal. The CuS 2 N arrangement in the complex is further stabilised by NH…N(thiocyanate) H bonds (N…N=3.060 A; NH…N=160°). The final conventional R index is 0.057 for 1308 observed reflections (F⩾4σ(F)). The IR spectrum of the complex is indicative of a CuS 2 N arrangement with v (CuS) at 245 cm −1 . Thermal decomposition of the complex in air (150- 740 °C) involves desulphurisation of the imdtH 2 ligands and thiocyanate anions together with in situ copper sulphide production (150–560 °C) followed by degradation to copper(II) oxide (620–740 °C).

Preparation, spectroscopy and crystal structure of a novel tetranuclear copper(I) benzimidazoline-2-thione complex: cyclo-hexakis-μ2-(benzimidazoline-2-thione) tetrakis[benzimidazoline-2-thione copper(I)] perchlorate quatrodeca hydrate

Abstract Reaction between copper(II) perchlorate and benzimidazole-2-thione (bzimztH) in aqueous ethanol produced a pale green crystalline solid of empirical formula [Cu2(bzimztH)5](ClO4)2·7H2O. The compound is diamagnetic at room temperature and possesses no d-d absorption in its electronic spectrum. The crystal structure of the compound contains centrosymmetrically constrained tetranuclear cations [Cu4(bzimztH)10]4+, perchlorate anions and water molecules in a monoclinic unit cell [a = 14.960(2), b = 25.863(3), c = 14.031(2) A, β = 110.331(8)°, space group P21/c, Z = 2]. The tetranuclear cations contain a planar centrosymmetric array of copper(I) atoms, Cu4, with edge dimensions of 2.681(2) and 4.216(3) A and an internal angle of 85.8(1)°. Each copper(I) atom is tetrahedrally coordinated by four S-donating ligands. The ten ligands in the cation consists of four terminal S-donating, one asymmetric μ2-S bridging ligand along each of the long edges of the Cu4 array and four asymmetric μ2-S bridging ligands arranged in pairs along each of the short edges of the Cu4 array. The latter generate pairs of Cu2S2 units narrow angles at the bridging S atoms, 69.1(1)° and 66.8(1)°. The remaining bridging angle is much larger, 124.9(1)°. CuS distances are in the range 2.262(2) to 2.499(3) A with the terminal distances somewhat shorter than the bridging ones. An alternating sequence of long and short CuS distances, created by the μ2-S bzimztH ligands, links the copper atoms of the Cu4 array. The final R index for 4672 observed reflections is 0.092.