A reaction between nickel(II) sulfate and hydrazine in aqueous solution yields blue crystals of [Ni-6(N2H4)(6)(SO4)(4)(OH)(2)(H2O)(8)] (SO4)(H2O)(10). The compound has been characterized by single, crystal and powder X-ray diffraction, vibrational spectroscopy, as well as variable-temperature magnetic susceptibility. This is the first reported crystal structure of the nickel(II) complex with hydrazine. The complex cation in the compound has a remarkable structure with unusual diversity of bridging groups including hydrazine molecules, sulfate ions, and hydroxo groups. Hydrazine molecules bridge nickel ions into trimers, which are further linked into hexamers through bridging sulfates. The magnetic susceptibility study of the compound reveals antiferromagnetic interaction between nickel(II) ions in the polynuclear complex.

The synthesis of thallium(III) chloride and bromide was performed in solution by chlorination and bromination, respectively, of the suspensions of the corresponding thallium(I) halides in acetonitrile. Crystalline compounds TlX3(CH3CN)(2) (X = Cl , Br) were prepared from the acetonitrile solutions. Thallium(III) chloride and bromide in dimethylsulfoxide solution were obtained by dissolving the corresponding solid compounds TlX3(CH3CN)(2) (Cl, Br) in DMSO. Both acetonitrile and dimethylsulfoxide solutions of thallium(III) chloride were studied by UV-Vis and Tl-205 NMR spectroscopy. The UV-Vis study of the TlCl3-CH3CN system showed presence of at least two thallium(III) chloride species. Only one signal arising from the thallium(III) species was, however, detected by the Tl-205 NMR in the solution because of the fast chemical exchange. The Tl-205 NMR study of thallium(III) chloride in dimethylsulfoxide showed three separate signals assigned to the solvated TlCl4-, TlCl3 and TlCl2+ species. The crystalline compounds of trichlorobis(dimethylsulfoxide) thallium(III) and tribromobis(dimethylsulfoxide) thallium(III) were prepared and their crystal structures were solved by single-crystal X-ray analysis. The thallium atom in the complexes has a trigonal bipyramidal environment built by three halide ions occupying equatorial positions of the polyhedron and two oxygen atoms of the DMSO molecules in the apical positions.

The ammonia solvated mercury(II) ion has been structurally characterized in solution by means of EXAFS, 199Hg NMR, and Raman spectroscopy and in solid solvates by combining results from X-ray single crystal and powder diffraction, thermogravimetry, differential scanning calorimetry, EXAFS, and Raman spectroscopy. Crystalline tetraamminemercury(II) perchlorate, [Hg(NH 3)4](ClO4)2, precipitates from both liquid ammonia and aqueous ammonia solution, containing tetraamminemercury(II) complexes. The orthorhombic space group (Pnma) imposes Cs symmetry on the tetraamminemercury(II) complexes, which is lost at a phase transition at about 220 K. The Hg-N bond distances are 2.175(14), 2.255(16), and 2 x 2.277(9) Å, with a wide N-Hg-N angle between the two shortest Hg-N bonds, 122.1(7)°, at ambient temperature. A similar distorted tetrahedral coordination geometry is maintained in liquid ammonia and aqueous ammonia solutions with the mean Hg-N bond distances 2.225(12) and 2.226(6) Å, respectively. When heated to 400 K the solid tetraamminemercury(II) Perchlorate decomposes to diamminemercury(II) Perchlorate, [Hg(NH3) 2](ClO4)2, with the mean Hg-N bond distance 2.055(6) Å in a linear N-Hg-N unit. The mercury atoms in the latter compound form a tetrahedral network, connected by perchlorate oxygen atoms, with the closest Hg?Hg distance being 3.420(3) Å. The preferential solvation and coordination changes of the mercury(II) ion in aqueous ammonia, by varying the total NH3:Hg(II) mole ratio from 0 to 130, were followed by 199Hg NMR. Solid [Hg(NH3)4](ClO 4)2 precipitates while [Hg(H2O) 6]2+ ions remain in solution at mole ratios below 3-4, while at high mole ratios, [Hg(NH3)4]2+ complexes dominate in solution. The principal bands in the vibrational spectrum of the [Hg(NH3)4]2+ complex have been assigned. © 2008 American Chemical Society.

The photochemistry of binuclear metal-metal bonded complexes [(NC) 5Pt-Tl(Solv)x] (solv is water or dimethylsulfoxide) has been studied in aqueous and dimethylsulfoxide solutions. Both stationary and nanosecond laser flash photolysis have been carried out on the species. The metal-metal bonded complexes have been photolyzed by irradiation into the corresponding intense MMCT absorption bands. Photoexcitation results in the cleavage of the platinum-thallium bond and the formation of a solvated thallous ion and a cyano complex of platinum(IV), [Pt(CN)5(Solv)]-, in both cases. The species have been characterized by multinuclear NMR and optical spectroscopy. The products of the photoreaction indicate a complementary two-electron transfer occurring between platinum and thallium ions in the binuclear Pt-Tl species. Quantum yield values for the photodecomposition of the species have been determined. The intermediates of the photoinduced metal-to-metal electron transfer have been detected and characterized by optical spectroscopy. The kinetics of transient formation and decomposition have been studied, and mechanisms of the photoactivated redox reaction have been suggested. © 2008 American Chemical Society.

Liquid ammonia, trialkyl phosphites, and especially trialkylphosphines, are very powerful electron-pair donor solvents with soft bonding character. The solvent molecules act as strongly coordinating ligands towards mercury(ii), interacting strongly enough to displace halide ligands. In liquid ammonia mercury(ii) chloride solutions separate into two liquid phases, the upper contains tetraamminemercury(ii) complexes, [Hg(NH3)4] 2+, and chloride ions in low concentration, while the lower is a dense highly concentrated solution of [Hg(NH3)4] 2+ entities, ca. 1.4 mol dm-3, probably ion-paired by hydrogen bonds to the chloride ions. Mercury(ii) bromide also dissociates to ionic complexes in liquid ammonia and forms a homogeneous solution for which 199Hg NMR indicates weak bromide association with mercury(ii). When dissolving mercury(ii) iodide in liquid ammonia and triethyl phosphite solvated molecular complexes form in the solutions. The Raman ?(I-Hg-I) symmetric stretching frequency is 132 cm-1 for the pseudo-tetrahedral [HgI 2(NH3)2] complex formed in liquid ammonia, corresponding to DS = 56 on the donor strength scale. For the Hg(ClO4)2/NH4I system in liquid ammonia a 199Hg NMR study showed [HgI4]2- to be the dominating mercury(ii) complex for mole ratios n(I-): n(Hg 2+) 6. A large angle X-ray scattering (LAXS) study of mercury(ii) iodide in triethyl phosphite solution showed a [HgI2(P(OC 4H9)3)2] complex with the Hg-I and Hg-P bond distances 2.750(3) and 2.457(4) Å, respectively, in near tetrahedral configuration. Trialkylphosphines generally form very strong bonds to mercury(ii), dissociating all mercury(ii) halides. Mercury(ii) chloride and bromide form solid solvated mercury(ii) halide salts when treated with tri-n-butylphosphine, because of the low permittivity of the solvent. A LAXS study of a melt of mercury(ii) iodide in tri-n-butylphosphine at 330 K resulted in the Hg-I and Hg-P distances 2.851(3) and 2.468(4) Å, respectively. The absence of a distinct I-I distance indicates flexible coordination geometry with weak and non-directional mercury(ii) iodide association within the tri-n-butylphosphine solvated complex. This journal is © The Royal Society of Chemistry.

The new crystalline compounds Tl2Ni(CN)4 and Tl 2Pd(CN)4 were synthesized by several procedures. The structures of the compounds were determined by single-crystal X-ray diffraction. The compounds are isostructural with the previously reported platinum analogue, Tl2Pt(CN)4. A new synthetic route to the latter compound is also suggested. In contrast to the usual infinite columnar stacking of [M(CN)4]2- ions with short intrachain M-M separations, characteristic of salts of tetracyanometalates of NiII, Pd II, and PtII, the structure of the thallium compounds is noncolumnar with the two TlI ions occupying axial vertices of a distorted pseudo-octahedron of the transition metal, [MTl2C 4], The Tl-M distances in the compounds are 3.0560(6), 3.1733(7), and 3.140(1) Å for NiII, PdII, and PtII, respectively. The short Tl-Ni distance in Tl2Ni(CN)4 is the first example of metal-metal bonding between these two metals. The strength of the metal-metal bonds in this series of compounds was assessed by means of vibrational spectroscopy. Rigorous calculations, performed on the molecules in D4h point group symmetry, provide force constants for the Tl-M stretching vibration constants of 146.2, 139.6, and 156.2 N/m for the Ni II, PdII, and PtII compounds, respectively, showing the strongest metal-metal bonding in the case of the Tl-Pt compound. Amsterdam density-functional calculations for isolated Tl2M(CN) 4 molecules give Tl-M geometry-optimized distances of 2.67, 2.80, and 2.84 Å for M = NiII, PdII, and PtII, respectively. These distances are all substantially shorter than the experimental values, most likely because of intermolecular Tl-N interactions in the solid compounds. Time-dependent density-functional theory calculations reveal a low-energy, allowed transition in all three compounds that involves excitation from an a1g orbital of mixed Tl 6pz-M nd z2 character to an a2u orbital of dominant Tl 6pz character. © 2007 American Chemical Society.

The reactions of [Pt(NH3)2(NHCOtBu) 2] and TlX3 (X = NO3-, Cl -, CF3CO2-) yielded dinuclear [{Pt(ONO2)(NH3)2-(NHCOtBu)} Tl(ONO2)2(MeOH)] (2) and trinuclear complexes [{PtX(RNH2)2(NHCOtBu)2} 2Tl]+ [X = NO3- (3), Cl- (5), CF3CO2- (6)], which were spectroscopically and etructurally characterized. Strong Pt-Tl interaction in the complexes in solutions was indicated by both 195Pt and 205Tl NMR spectra, which exhibit very large one-bond spin-spin coupling constants between the heteronuclei (1JPtTl), 146.8 and 88.84 kHz for 2 and 3, respectively. Both the X-ray photoelectron spectra and the 195Pt chemical shifts reveal that the complexes have Pt centers whose oxidation states are close to that of PtIII. Characterization of these complexes by X-ray diffraction analysis confirms that the Pt and Tl atoms are held together by very short Pt-Tl bonds and are supported by the bridging amidate ligands. The Pt-Tl bonds are shorter than 2.6 Å, indicating a strong metal-metal attraction between these two metals. Compound 2 was found to activate the C-H bond of acetone to yield a platinum(IV) acetonate complex. This reactivity corresponds to the property of PtIII complexes. Density functional theory calculations were able to reproduce the large magnitude of the metal-metal spin-spin coupling constants. The couplings are sensitive to the computational model because of a delicate balance of metal 6s contributions in the frontier orbitals. The computational analysis reveals the role of the axial ligands in the magnitude of the coupling constants. © 2006 American Chemical Society.

Three adducts have been prepared from Hg(CN)2 and square planar MII(CN)42- transition metal cyanides (M = Pt, Pd, or Ni, with d8 electron shell) as solids. The structure of the compounds K2PtHg(CN)6·2H2O (1), Na 2PdHg-(CN)6·2H2O (2), and K 2NiHg(CN)6·2H2O (3) have been studied by single-crystal X-ray diffraction, XPS, Raman spectroscopy, and luminescence spectroscopy in the solid state. The structure of K2PtHg(CN) 6·2H2O consists of one-dimensional wires. No CN- bridges occur between the heterometallic centers. The wires are strictly linear, and the Pt(II) and Hg(II) centers alternate. The distance dHg-Pt is relatively short, 3.460 Å. Time-resolved luminescence spectra indicate that Hg(CN)2 units incorporated into the structure act as electron traps and shorten the lifetime of both the short-lived and longer-lived exited states in 1 compared to K2[Pt(CN) 4]·2H2O. The structures of Na2PdHg-(CN) 6·2H2O and K2NiHg(CN) 6·2H2O can be considered as double salts, the lack of heterometallophilic interaction between the remote Hg(II) and Pd(II) atoms, 4dHg-Pd = 4.92 Å, and Hg(II) and Ni(II) atoms, d Hg-Ni = 4.61 Å, is apparent. Electron binding energy values of the metallic centers measured by XPS show that there is no electron transfer between the metal ions in the three adducts. In solution, experimental findings clearly indicate the lack of metal-metal bond formation in all studied Hg II-CN--MII(CN)42- systems (M = Pt, Pd, or Ni). © 2005 American Chemical Society.

Thallium(III) oxide can be dissolved in water in the presence of strongly complexing cyanide ions. TlIII is leached from its oxide both by aqueous solutions of hydrogen cyanide and by alkali-metal cyanides. The dominating cyano complex of thallium(III) obtained by dissolution of Tl 2O3 in HCN is [Tl(CN)3(Bq)] as shown by 205Tl NMR. The Tl(CN)3 species has been selectively extracted into diethyl ether from aqueous solution with the ratio CN -/TlIII = = 3. When aqueous solutions of the MCN (M = Na+, K+) salts are used to dissolve thallium(III) oxide, the equilibrium in liquid phase is fully shifted to the [Tl(CN) 4]- complex. The Tl(CN)3 and Tl(CN) 4- species have for the first time been synthesized in the solid state as Tl(CN)3·H2O (1), M[Tl(CN) 4] (M = Tl (2) and K (3)), and Na[Tl(CN)4]·3H 2O (4) salts, and their structures have been determined by single-crystal X-ray diffraction. In the crystal structure of 1, the thallium(III) ion has a trigonal bipyramidal coordination with three cyanide ions in the equatorial plane, while an oxygen atom of the water molecule and a nitrogen atom from a cyanide ligand, attached to a neighboring thallium complex, form a linear O-Tl-N fragment. In the three compounds of the tetracyano-thallium(III) complex, 2-4, the [Tl(CN)4]- unit has a distorted tetrahedral geometry. Along with the acidic leaching (enhanced by TlIII-CN- complex formation), an effective reductive dissolution of the thallium(III) oxide can also take place in the Tl 2O3-HCN-H2O system yielding thallium(I), while hydrogen cyanide is oxidized to cyanogen. The latter is hydrolyzed in aqueous solution giving rise to a number of products including (CONH2) 2, NCO-, and NH4+ detected by 14N NMR. The crystalline compounds, TlI[Tl III(CN)4], TlI2C2O 4, and (CONH2)2, have been obtained as products of the redox reactions in the system. © 2005 American Chemical Society.

The solvation of the mercury(II) ion in solvents with different solvation properties, water, dimethylsulfoxide, N,N-dimethylthioformamide, and liquid ammonia, has been studied by means of 199Hg NMR. The 199Hg chemical shift shows a pronounced dependence on the coordination number of the mercury(II) ion in the solvates resulting in a difference of over 1200 ppm between basically tetrahedral and octahedral complexes. The chemical shifts can furthermore be associated with electron-pair donor properties of the solvents. The spin-lattice relaxation times of the 199Hg nucleus in the solvates have been measured at different applied magnetic fields, concentrations, temperatures, and isotope substitutions. Possible mechanisms for the 199Hg relaxation were proposed and the chemical shielding anisotropy in the solvates has been estimated. The 199Hg relaxation rates and the anisotropy are correlated with the structure of the solvate complexes in solution obtained from recent LAXS and EXAFS studies. Copyright © 2005 John Wiley & Sons, Ltd.