Proton NMR spectra and structure of chlorotin(IV) ternary complexes of 8-quinolinol and its 5,7 dichloro and 2 methyl-5,7 dichloro derivatives

The low temperature ¹H NMR spectra in d-chloroform of the ternary complexes bis-(8-quinolinato) tin(IV) dichloride, bis-(5,7 dichloro-8-quinolinato) tin(IV) dichloride, and bis-(2 methyl-5,7-dichloro-8-quinolinato) tin(IV) dichloride have been obtained. The spectra showed that for the three complexes, only two configurations were appreciably populated, their free energy differences being equal to 0.28, 0.08 and ?0.04 kcal/mol respectively. The proton chemical shifts, the ¹H-¹H coupling constants and some of the ¹H-¹¹⁹Sn coupling constants have been obtained for each complex in the two configurations. An approximate computation of chemical shifts, including aromatic ring magnetic anisotropies and electric effects from polar groups, allowed the identification of the two configurations as the cis-cis-trans and the cis-trans-cis (with respect to Cl, N and O atoms), the former being the more populated one.     

Dissociation of uranium(III) and uranium(IV) borohydrides in solution: 11B, 1H NMR study

Uranium(III) borohydride, which can be prepared in THF solution, and uranium(IV) borohydride are found to undergo dissociation to give cationic and anionic species:

these species are identified by their ¹H and ¹¹B NMR spectra. BH^?₄ is found to be in exchange between the three species in both cases.     

NMR investigation of bis(2,3-alkanedione dioximato)-bis(pyridine)cobalt(III) iodide complexes: 1H and 13C NMR spectra and 13C spin-lattice relaxation time measurements

The complexes of trans-[Co(III)(R,CH₃-dioxH)₂(py)₂]I2 (R = CH₃, C₂H₅, n-C₃H₇ and n-C₄H₉) were investigated in solution by ¹H and ¹³C NMR spectra and ¹³C spin-lattice relaxation time measurements. The ¹H and ¹³C-resonances of the R = C₂H₅, n-C₃H₇ and n-C₄H₉) groups were shifted to higher field than those of the free ligands by the complexation; it was attributable to the ring current shielding due to the axial pyridine ligands of the complexes. ¹³C spin-lattice relaxation times were interpreted as due to movement of the axial pyridine ligands as if they twist around the CoN (pyridine nitrogen) bond axis and the above R groups were moving segmentally. These segmental movements allowed the R groups to approach closely toward the axial pyridine ring plane to experience the ring current shielding.     

119Sn mössbauer,IR, 1H NMR spectroscopic and thermal decomposition studies on organotin(IV) adducts with glycylglycine

The complexes R₂SnCl₂·(H₂glygly), (H₂glygly = glycylglycine) (R = Me, Buⁿ, Octⁿ, Ph) and RSnCl₃·(H₂glygly)     

NMR (195Pt and 13C) contribution to the study of some Pt(II), Pt(IV) and mixed-valence thioamido complexes

The ¹⁹⁵Pt and ¹³C chemical shifts (δ_Pt and δ_c) are reported for platinum(II), platinum(IV) and class II mixed-valence complexes, with general formula [PtL₄]X₂, cis- and trans-PtL₂X₂, PtL₂X₄ and Pt₂L₄X₆ (where L may be thiourea, 2-imidazolidine-thione, tetrahydro 2-pyrimidinethione, thiocaprolactam, pyridine-2-thione and tetramethylthiourea, and X may be Cl or Br). The ¹⁹⁵Pt chemical shifts can be understood in view of ¹³C data in terms of variations of electronegativities and σ-donor abilities of ligands attached to platinum.     

Effects of chemical shift anisotropy and 14N coupling on the 1H and 195Pt nuclear magnetic resonance spectra of platinum complexes

Broadening of the ¹⁹⁵Pt satellites in the ¹H NMR spectrum of trans-Pt(ethene)(2-carboxy-pyridine)Cl₂ at high field arises from relaxation of ¹⁹⁵Pt via the chemical shift anisotropy mechanism. We also demonstrate that well-resolved ¹⁴N-¹⁹⁵Pt couplings can be observed in ¹⁹⁵Pt NMR spectra of Pt(II) and Pt(IV) amine complexes, including anti-tumour agents, at elevated temperature where scalar coupling contributions to ¹⁹⁵Pt relaxation are much reduced.     

N, C and Sn NMR and other spectroscopic studies of 8-quinolinol, its O- and N-methyl derivatives, and chelate di- and tri-organotin(IV) complexes

The nature of the 8-quinolinato ligand in various forms has been examined by ¹⁵N, ¹³C and ¹¹⁹Sn NMR spectroscopy, with evidence also from electronic spectroscopy. These forms include 8-quinolinol (HQ), 8-quinolinate, the 8-hydroxyquinolinium ion, O- and N-methyl derivatives, 8-methoxyquinoline (MeQ), the zwitterionic N-methylquinolinium-8-olate and the N-methylquinolinium ion, and the chelating ligand in organotin(IV) complexes. The ¹⁵N shift from MeQ to HQ affords a measure of the intramolecular hydrogen bonding in HQ. The ¹⁵N shifts and ²J(¹⁵N¹H) couplings afford criteria of chelation, and the O- and N-methyl compounds provide useful reference points for its assessment. Evidence for chelation is demonstrated in three groups of compounds, [SnR₂Q₂] (R = Me, Et, Buⁿ, Octⁿ or Ph), [SnR₃Q] (R = Me, Et, Buⁿ or Ph) and [SnR₂ClQ] (R = Me, Et, Buⁿ or Octⁿ), the ¹⁵N and ¹¹⁹Sn shielding increasing from the [SnR₃Q] to the [SnR₂Q₂] compounds.     

Photosubstitution in some cyanide complexes of chromium(III)(1)

Photosubstitution by OH^? ligand was concluded from a photochemical study of the [Cr(CN)₆]^3? and [Cr(CN)₅OH]^3? complexes in alkaline medium. Photoaccelerated aquation was found to proceed in the case of aquocyanochromates(III): [Cr(CN)₅H₂O]^2? and [Cr(CN)₃(H₂O)₃].     

17O and 183W NMR studies of the paratungstate anions in aqueous solutions

¹⁷O (40.7 MHz) and ¹⁸³W (12.5 MHz) NMR spectra of aqueous Na₁₀[H₂W₁₂O₄₂]·27H₂O (1), Na₆[W₇O₂₄]·14H₂O (2) and (NH₄)₆[Mo₇O₂₄]·nH₂O solutions, as well as of 2, 1 and 0.1 M Na₂WO₄ and 2 M Li₂WO₄ solutions acidified up to P = 0.5, 1 and 1.14 have been measured. The composition of the W₇O₂₄^6? anion remains unchanged (2), its structure being similar to that of Mo₇O₂₄^6?183W NMR spectrum shows three resonances with the chemical shifts + 269.2, ?98.8 and ?178.9 ppm relative to WO₄^2? and intensity ratio 1:4:2. “Paratungstate A” produced during polycondensation of WO₄^2? at P ? 1.17 is identical with heptatungstate W₇O₂₄^6?. The [H₂W₁₂O₄₂]^10?183W NMR spectrum in the acidified 2 M Li₂WO₄ solution has four resonances with the chemical shifts in the range - 105–145 ppm and intensity ratio 1:2:1:2. As suggested by NMR data, the H₂W₁₂O₄₂^10? ? W₇O₂₄^6? transformations occur, which depend upon concentration and temperature.     

13C NMR study of dilute ternary solutions: Acetonitrile,silver nitrate and other electrolytes in water at 25°C

The ¹³C NMR chemical shifts have been measured for dilute aqueous solutions of acetonitrile in presence of various electrolytes including silver nitrate. The two formation constants of the silver ion/acetonitrile complexes have been calculated assuming an additive contribution of each possible complex configuration. Under these conditions the values obtained for the formation constants are very close to those deduced from vapour pressure or electromotive force techniques. The other systems studied are discussed in relation to the salting phenomenon in aqueous electrolyte solutions.     

Photochemistry of aqueous [W(CN)8]4−

Aqueous [W(CN)₈]^4? undergoes photoaquation when irradiated at ～ 365 nm with pH independent quantum yield. The yield for aquoheptacyanotungstate (IV) ion production is 0.8 at 0.5°C. If added alkali is present a wide variety of products [W(CN)₇(OH)]^4?, [WO₂(CN)₄]^4?, [WO(OH)(CN)₄]^3? [W(OH)₂(CN)₄]^2? are formed.     

Steric effects in 29Si and 13C NMR spectra of trimethylsilyl- and alkyl-substituted benzenes

²⁹Si and ¹³C NMR spectra of trimethylsilylbenzenes substituted at different positions by methyl and trimethylsilyl groups were investigated with special reference to steric interactions between the ortho-substituents. The steric effects, as measured by ¹³C and ²⁹Si chemical shifts, are generally smaller in trimethylsilyl- than in t-butyl-substituted compounds. Both nuclei follow the same general trends in the benzene derivatives.     

Coordination chemistry of new sulphur containing ligands—26. Eight coordinate vanadium(IV) and molybdenum(IV) complexes of 2-amino-1-cyclopentenedithiocarboxylate1

The new difunction ligand, 2-amino-1-cyclopentenedithio-carboxylate(L), was prepared and its coordination chemistry examined to gain further insight into the reactivity of “aromatic” dithio type ligands. Reaction with MoCl₄py₂ and VOSO₄, led to the surprising eight coordinate products ML₄. The sp² hybridization of the ring carbon to which the CS₂ moiety is bonded apparently yields a pseudo-aromatic effect on the reactivity of this ligand. The physical properties of these new compounds are discussed.     

Pressure dependence of 35Cl NQR in hexachloro- (N3P3Cl6) and octachloro- (N4P4Cl8) cyclophosphazenes

High pressure studies of ³⁵Cl NQR in the hexachlorocyclophosphazene N₃P₃Cl₆ and in the K- and T-forms of octachlorocyclophospha     

Platinum-195 NMR studies of Pt(LL)2 (LL = −S2PR2, −S2P(OR)2, −S2CNR2) and their derivatives with phosphorus containing ligands

Platinum-195 NMR spectra have been recorded for CH₂Cl₂ solutions of a range of Pt(LL)₂ (LL = ^?S₂PR₂, ^?S₂P(OR)₂, ^?S₂CNR₂) and their derivatives with phosphorus containing ligands. Platinum chemical shifts cover a range of almost 2000 ppm.     

Synthesis, 13C NMR and IR spectroscopic studies of gold(I) complexes of imidazolidine-2-thione and its derivatives

The gold(I) complexes of imidazolidine-2-thione and its derivatives were synthesized and their ¹³C NMR and IR spectroscopic studies were carried out. When gold(III) was reacted with the ligands using a 1:4 metal to ligand ratio, gold(III) was reduced to gold(I), the bis complexes of the general formula AuL_nX (where n = 2) were formed. However, when gold(III) was reduced to gold(I) by a reducing agent followed by an addition of the ligand to an aqueous or methanolic solution of gold(I), only mono complexes of the type AuLX were obtained. The structures of the reported complexes are proposed on the basis of their spectroscopic measurements.     

Pentamethylcyclopentadienylplatinum(IV) complexes

Reaction of dichloro(η⁴-pentamethylcyclopentadiene)platinum with bromine yields a η⁵-pentamethylcyclopentadienylplatinum(IV) complex which is formulated as [C₅Me₅PtBr₃PtC₅Me₅]Br₃.     

the 31P NMR chemical shifts of four-, five- and six-coordinate phosphorus(V) compounds

There appears to be a correlation between the ³¹P chemical shift differences between A⁺ and AX (Δ₁), and between A⁺ and AX₂^? (Δ₂), where A⁺ is a phosphonium ion and X is an anionic ligand. This relationship holds for a wide range of substituents on phosphorus, despite the expected changes in hybridisation along the series, and is very useful for predicting the shifts of new or unknown species.     

Further studies of phosphine adducts of niobium(IV) and tantalum(IV) chlorides: New seven- and eight-coordinate compounds with trimethylphosphine: NbCl4(PMe3)3 and Ta2Cl8(PMe3)4

The reaction of NbCl₄(THF)₂ with an excess of PMe₃ in toluene solution afforded a 70% isolated yield of green NbCl₄(PMe₃)₃. When a slurry of TaCl₅ in toluene containing a slight excess of PMe₃ was reduced with sodium amalgam overnight, a 60% yield of orange to red (depending on crystal size) Ta₂Cl₈(PMe₃)₄ was obtained. Both compounds have been fully characterized by X-ray crystallography. NbCl₄(PMe₃)₃ forms monoclinic crystals (P2₁/c) with unit cell dimensions a = 15.061(3) Å, b = 11.677(4) Å, c = 11.583(4) Å, β = 91.71(3)°, V = 2036(2) ų, and Z = 4. It is isomorphous with its TaCl₄(PMe₃)₃ homolog, and the bond lengths and angles are very similar. Ta₂Cl₈(PMe₃)₄ forms cubic crystals (Im3) with a = 16.377(2), V = 4392(2) ų and Z = 6. It is thus isomorphous with its niobium homolog, and the internal dimensions are quite comparable. The Ta-Ta distance is 2.830(1) Å, consistent with the existence of a single bond.     

121Sb Mössbauer spectral and related studies on Sb(III) complexes

The bonding and structural features of antimony(III) complexes of the type, (PrⁱO)SbL and Sb₂L₃ are described (where L is the dianion of semicarbazone or thiosemicarbazone). The Mössbauer spectra are typical of Sb(III) complexes in which the non-bonding pair of electrons is stereochemically active. The thiosemicarbazone complexes show more negative isomer shifts compared to the semicarbazone complexes.