Julius Glaser

17O and 1H NMR study of the tetranuclear hydroxo zirconium complex in aqueous solution

Abstract The tetrameric hydroxo zirconium(IV) complex in aqueous solution has been studied by means of 17 O and 1 H NMR. For the first time, an 17 O NMR signal from oxygens coordinated to Zr in this complex has been observed. This signal, at ∼ 180 ppm, corresponds to ∼ 2 O/Zr and has been assigned to two strongly bound terminal water molecules. Exchange of these waters with the bulk water takes a few months, as found by addition of 17 O- enriched water. In 1 H NMR spectra, besides the bulk water signal, a signal at 7.9 ppm has been observed at room temperature and assigned to slowly exchanging protons, 2H/Zr, of the terminal water molecules in the tetramer. The lifetime of a specific proton of this type is unusually long for inorganic coordination compounds in aqueous solution, ≈ 0.1 s in 2.2 M Zr solution at room temperature. On this basis, the formula of the tetramer in aqueous solution should be written [Zr 4 (OH) 8 (H 2 O) I 8 (H 2 O) II 8 ] 8+ i.e. there are two inert and two labile water molecules per Zr. Up to two of the coordinated water protons are so easily dissociated that this species constitutes a very strong acid. One of the inert water molecules is replaced completely upon addition of one nitrate per Zr. Addition of acetone to an aqueous solution of the tetramer leads to coordination of acetone to the tetramer.

Advances in Thallium Aqueous Solution Chemistry

Publisher Summary This chapter discusses thallium, especially Tl (III), which has much interesting solution chemistry. The increasing interest in thallium chemistry is because of several distinct applications. Besides the redox properties used in organic preparative chemistry and for model studies of electron transfer reactions, it can be perceived that thallium has found applications as a model for the general behavior of metal ions. The chemistry of thallium has also been investigated for its potential contribution to environmental pollution. Recent research on thallium compounds has been stimulated by the preparation of several thallium-containing high-temperature superconductors. Thallium (II) can be produced in aqueous solution by reduction of Tl (III) with hydrogen atoms or by radiolysis of aqueous solutions of Tl (I). The starting solution employed for the investigation of aqueous thallium (III) compounds can be prepared by dissolving commercial Tl2O3 in a mineral acid. More concentrated solutions are prepared by oxidation of thallium (I) compounds. Although the oxidation of the thallium (I) halide compounds poses no problems when oxidation is by the corresponding halogen, the preparation of noncomplexed Tl3+ is less straightforward.

A NEW CLASS OF OLIGONUCLEAR PLATINUM-THALLIUM COMPOUNDS WITH A DIRECT METAL-METAL BOND. 3. UNUSUAL EQUILIBRIA IN AQUEOUS SOLUTION

A new series of four binuclear platinum-thallium cyano compoundscontaining a direct and unsupported by ligands metal2metalbond has been prepared in aqueous solution. Thesecompounds are represented by the formula[(NC)5Pt2Tl(CN)n21](n21)2 (n = 124 for compounds I, II, IIIIV, respectively) and [(NC)5Pt2Tl2Pt(CN)5]32 (for compoundV). The oligonuclear complexes are synthesised accordingto the reaction mPt(CN)422 + Tl3+ + nCN2 v [PtmTl-(CN)4m+n]322m2n. Thus, there occurs a change of the coordinationnumber of the Pt center from four (square planar) tosix (octahedral). Consequently, the formation of binuclearplatinum-thallium cyano compounds involves at least twosteps: (i) formation of metal2metal bond and (ii) formation of(NC)5Pt2 unit by a cyanide transfer process. 2 The complexes exist in an equilibrium, which also includes the parentcomplexes Pt(CN)422 and Tl(CN)n32n (n = 024), and can becontrolled by varying the cyanide concentration and/or pHof the solution. The stability constants of the compounds âN =[PtmTl(CN)4m+n322m2n] / {[Pt(CN)422]m· [Tl3+] ·[CN2]n} havebeen determined by means of multinuclear NMR (195Pt,205Tl): logâN = 19.9±0.4, 30.7±0.3, 38.6±0.3, and 44.8±0.2 forI, II, III, and IV (m = 1, n = 124), and 32.1±0.3 for V (m = 2,n = 2), respectively, (in 1 M NaClO4 as ionic medium, at 25oC). To our knowledge, the present work constitutes the firstdetailed equilibrium study of metal2metal bonded compounds;it indicates that also other cluster formation reactionsdescribed in the literature may represent real equilibria.

Multinuclear Magnetic Resonance (1H, 11B, 13C, 15N and 205Tl) Study of Thallium Hydridotris(3,5‐dimethylpyrazol‐1‐yl)borate

One of the frequently used ligands, hydri‐dotris ( 3, 5 ‐ dimethylpyrazol ‐ 1 ‐ yl ) borate, and its thallium complex were fully characterized by multinuclear NMR. New 15N,205Tl coupling constants were measured. A dynamic process, with an activation energy of 65 kJ mol−1, which corresponds to the nitrogen–thallium bond breaking, is observed in these compounds.

Equilibrium and structure of thallium(III) -ethylenediamine complexes in pyridine solution and in solid

The formation of three [TI(en)(n)](3+) complexes (n = 1-3) in a pyridine solvent has been established by means of Tl-205 and H-1 NMR. Their stepwise stability constants based on concentrations, K-n ...

A 103Rh nuclear magnetic resonance study of rhodium(III) bromide complexes in aqueous solution

The 103Rh NMR signals of all ten monomeric aquabromorhodium(III) complexes, [RhBrn(OH2)6–n]3–n with n= 0–6, including the geometric isomers for n= 2–4, have been assigned. The chemical shifts δRh of these complexes demonstrate a nephelauxetic dependence, namely a decrease in δ with an increase in the number of bromo ligands. For the geometrical isomers it has been shown that δtrans > δcis and δmer > δfac. Evidence is given for the existence of oligomeric aquabromorhodate(III) species and structural characteristics are proposed consistent with the observed chemical shifts. The 103Rh NMR chemical shift has been measured for the aqueous [Rh(NH3)6]3+ complex (δRh= 4766 at 276 K) and, together with other six-co-ordinated rhodium(III) complexes, correlated with the ligand-field parameter ratio β/ΔE, where β is the nephelauxetic ratio and ΔE the electronic transition energy for octahedral complexes, 1A1gâ†�1T1g. Linear regression gives an estimate of the core-electron diamagnetic shift to δRhd=–5000(1000).

Small Platinum−Thallium Clusters Stabilized by Ethylenediamine, [(NC)5Pt−Tl(en)n−1] (n = 1−3) − Characterization in Solution and in the Solid State

Three neutral binuclear platinum-thallium compounds containing a direct and naked (unsupported by ligands) metal-metal bond have been prepared in dimethyl sulfoxide (DMSO). The compounds have the formula [(NC)(5)Pt-Tl(en)(n-1)] (n = 1-3, for compounds 1, 2 and 3, respectively) and were found to exist in solution by means of multinuclear NMR (Pt-195, Tl-205, C-13 and H-1) and Raman spectroscopy. The compounds exhibit very large single bond Pt-195-Tl-205 spin-spin coupling constants of 48-66 kHz. In addition, the solid state analogues of 1 and 3, [(NC)(5)Pt-Tl(DMSO)(4)](DMSO) and [(NC)(5)Pt-Tl(en)(2)]-(DMSO)(2), were synthesized and their structures determined by single crystal X-ray diffraction. The metal-metal bond lengths of Pt-Tl are 2.6131(4) Angstrom and 2.6348(5) Angstrom in compounds I and 3, respectively. Crystal data for compound 1: monoclinic, space group Cc (No. 9), Z = 4, a = 17.2367(14), b = 9.5560(11), c = 17.7941(15) Angstrom, beta = 100.551(10)9 V = 2881.4(5) Angstrom (3), T = 110(1) K; and for compound 3: monoclinic, space group P2(1) (No. 4), Z = 2, a 9.3167(14), b 12.3007(13), c = 11.4586(16) Angstrom, beta = 112.318(16)degrees, V =1214.8(3) Angstrom (3), T = 110(1) K.

Novel bis(diethylenetriamine)thallium(III) complex. Synthesis and characterization in pyridine solution and in solid

A new complex of thallium(III) with the nitrogen donor ligand diethylenetriamine (dien) has been prepared and characterized by multinuclear NMR ( 1 H, 13 C, 205 Tl), infrared and Raman spectroscopy, and X-ray diffraction. In solution, the symmetric s-facial isomer of [Tl(dien)2] 3 + is formed. This is a fluxional molecule even at low temperature (235 K); therefore, the different rotamers cannot be observed separately. A complete characterization of the complex is given from its non-trivial NMR spectra. The crystal structure of [Tl(dien)2](ClO4)3·H2O shows u-facial geometry, where the coordination environment around thallium can be described as a distorted trigonal prism.

Rhodium(III) complexes with cyanide and sulfur-donor ligands: rhodium-103 nuclear magnetic resonance chemical shift correlations

The 103Rh NMR chemical shifts for hexa(cyano-κC)-, hexa(thiocyanato-κS)-rhodate(III) and tris(O,O′-diethyl dithiophosphato-κ2S,S′)rhodium(III) have been determined in aqueous solution. Two-bond spin–spin coupling is observed between 103Rh and 31P in the 103Rh NMR spectrum of [Rh{S2P(OEt)2}3], 2J(Rh–P)= 13 Hz. A value for the nephelauxetic ratio (β= 0.29 ± 0.05) was obtained for the [Rh(SCN)6]3– ion from a correlation between the 103Rh NMR chemical shifts of octahedral rhodium(III) complexes and the ligand-field parameter ratio, β/ΔE(1A1g–1T1g). Comparison with the nephelauxetic ratios of other S- and N-bonded complexes shows S-bonding between rhodium(III) and the thiocyanate ligand. An empirical correlation is demonstrated between the metal NMR chemical shift and the logarithm of the overall thermodynamic formation constant (log β6), for a range of octahedral rhodium(III) and cobalt(III) complexes, thus allowing the formation constants log β6= 47 ± 4 and 35 ± 3 to be estimated for [Rh(CN)6]3– and [Rh(SCN)6]3–, respectively. The stability of the aquafluororhodium(III) species is discussed. The thermodynamic basis for the dissolution of rhodium metal in aqueous solution using cyanide or thiocyanate is examined.

Formation, equilibrium properties and decomposition in aqueous solution of monoorganothallium(III) ions containing RC(O)CH2 groups. Preparation of monoaceteonylthallium(III) compounds

Abstract The reactions of thallium(III) with some ketones in the presence and absence of Cl − , Br − , CN − , CH 3 COO − and CF 3 COO − ions in acidic aqueous solution, and the stabilities of the resulting monoorganothallium(III) species in solution have been examined. the rate-determining step in the formation of these compounds is the acid-catalyzed enolisation of the ketones. The formation reactions are reversible: the ketonyl groups can be exchanged by Cl − , Br − , CN − and by other ketones. The equilibrium constant at 25°C for the reaction: H + + CH 3 C(O0CH 2 TlCl + + Cl − ⇌ TlCl 2 + + CH 3 C(O)CH 3 in about 1 molar HClO 4 was found to be 780 (±160) M −1 . This unusual behaviour of the Tl III -ketone systems can be accounted for by assuming that enolate complexes are present in low concentration, in equilibrium with the monoorganothallium(III) species. Two routes for decomposition of these species have been established. One of them takes place through RCH 2 C(O)CH 2 Tl 2+ ions and the other (when an excess of Cl − is present) through RCH 2 C(O)CH 2 TlCl + ions. The latter results in formation of α-monochlorinated product with the composition RCHClC(O)CH 3 (where R  R, alkyl, aryl), probably via a five-ring enolate intermdiate. Formation of diorganothallium(III) species of the type [RC(O)CH 2 ] 2 Tl + has also been demonstrated. Some new solid monoorganothallium(III) compounds with the composition ArC(O)CH 2 TlCl 2 (Ar  C 6 H 5 , 4′-ClC 6 H 4 , 4′-CH 3 C 6 H 4 , 2′-C 10 H 7 , RC(O)CH 2 -TlCl(NO 3 ) (R  CH 3 , (CH 3 ) 3 C) and (CH 3 ) 3 CC(O)CH 2 Tl( 2 CNEt 2 ) 2 have been prepared. 205 Tl NMR parameters for some mono- and di-organothallium(III) species are given.