Cumulated double bond systems as ligands : I. Dialkylsulfurdiimine compounds of platinum

The preparations and properties of a new series of compounds of the formula trans-[PtCl₂(dialkylsulfurdiimine)L] are reported. In the case of the dimethyl-, diethyl-, diisopropyl- and dineopentyl-sulfurdiimine platinum compounds two isomers are present in solution, but only one isomer was observed for the di-t-butylsulfurdiimine derivative. ¹H and ¹³C NMR data show that the two isomers interconvert intramolecularly by two different routes. In one of the isomeric forms, unusually large low-field chemical shifts indicate the existence of non-bonded metal—alkyl interactions.     

Cumulated double bond systems as ligands : III. 1H NMR studies of the intra- and inter-molecular exchange processes of dialkylsulfurdiimine compounds of palladium(II)

The preparation, properties and kinetic behaviour of trans-[PdCl₂(RNSNR)L] (L  PhMe₂As and Et₃As; R  Me, Et, i-Pr and t-Bu) are reported.In the case of R  t-Bu only one isomer, which participates in various intermolecular exchange reactions, is found. For R  Me, Et and i-Pr two isomers occur in solution. The most abundant isomer, which has a structure analogous to the t-butyl compound, is similarly involved in intermolecular exchange reactions of the sulfurdiimine. However, the second isomer, in which non-bonded Pd···HC interactions between the metal atom and the uncoordinated end of the sulfurdiimine group are probably present, does not participate in intermolecular exchange reactions if free sulfurdiimine is present. For this isomer fluxional behaviour is observed.     

13C Fourier transform studies of organotin compounds : I. 119Sn-13C spin-spin coupling constants

¹¹⁹Sn-¹³C coupling constants have been measured for fourteen organotin compounds including aliphatic, unsaturated and cyclic derivatives yielding results which indicate that these parameters have great potential for revealing information concerning structures and conformations of organotin compounds and of other compounds into which organotin groups can be conveniently introduced.     

A study of 4-carba-arachno-nonaborane(14) and the derived tridecahydro-4-carba-arachno-nonaborane(−1) anion: Structure and CH bond activation as shown by 1- and 2-D NMR

The ¹¹B and ¹H NMR spectra of the carbaborane CB₈H₁₄, and its anion CB₈H₁₃^?, have been recorded and assigned unambiguously by decoupling and COSY techniques. The results indicate the presence of unsymmetrical bridging hydrogen atoms in both the neutral and anionic species. More significantly the endo-hydrogen attached to the carbon atom is involved in exchange with all the three bridging hydrogen atoms in the CB₈H₁₃^? anion, whereas no such exchange is observed in the neutral CB₈H₁₄.     

Heteropoly compounds as octahedral high valence complex. Spectrochemical properties of Waugh-structure enneamolybdonickelate(IV) and enneamolybdomanganate(IV) ions

Electronic absorption and magnetic circular dichroism (MCD) spectra in UV-vis region of Waugh-structure [XMo₉O₃₂]^6?(X = Ni(IV), Mn(IV)) ion in aqueous solution and solid IR spectra have been measured. The Ni(IV) ion in the polyanion has a low-spin d⁶ electronic configuration and the Mn(IV) ion has a d³ configuration. Visible absorption spectrum of the nickelate(IV) polyanion is interpreted to be mainly governed by charge-transfer transitions of the “ligand”, Mo₉O₃₂, to Ni(IV) ion, rather than d-d transitions, while visible absorption of the manganate(IV) polyanion is governed, to a great extent, by d-d transitions. It is indicated by the MCD spectrum that the splitting of the first d-d absorption in the manganate(IV) polyanion is due to a contribution of the spin-forbiden transition, rather than from a trigonal splitting of the spin-allowed transition. Absorption and MCD spectra in UV region are due to charge-transfer transition within a common “ligand”, which are less influenced by the kind of heteroatom, Ni(IV) or Mn(IV). The MCD pattern by the intra-ligand charge-transfer is especially characteristic of the Waugh-structure polyanions.     

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.     

Benzene carbon-hydrogen bond activation using Ru(C6Me6)[PH(C6H11(2]H2

The dihydride Ru(C₆Me₆)[PH(C₆H₁₁)₂]H₂ is synthesized in high yield by reducing Ru(C₆Me₆)[PH(C₆H₁₁)₂]Cl₂ with Na[AlH₂(OCH₂CH₂OMe)₂]. In benzene it loses hydrogen under UV irradiation to give Ru(C₆Me₆)[PH(C₆H₁₁(₂]H(C₆H₅).     

New bimetallic organopalladium(II) compounds containing a PdCo or PdMo bond trans to a PdC bond

The reaction of a chelated palladium compound with Co(CO)^?₄ and [Mo(CO)₃-η-C₅H₅]^? gives new stable bimetallic PdCo and PdMo complexes in which the metal-metal bond is trans with respect to the Pd-carbon σ-bond.     

Ligand exchange processes in some iron-sulphur-carbonyl and -nitrosyl complexes

The complex [Fe₂(SMe)₂(CO)₆] undergoes stepwise exchange with Et₂S₂ to yield successively [Fe₂(SMe)(SEt)(CO)₆] and [Fe₂(SEt)₂(CO)₆]. Carbonyl complexes [Fe₂(SR)₂(CO)₆] are efficiently converted to the nitrosyls [Fe₂(SR)₂(NO)₄] by the action either of NO gas or of methanolic sodium nitrite: the analogous species [Fe₂S₂(CO)₆], [Fe₂S₂(CO)₆]^2?, and [Fe₃S₂(CO)₉] all, with methanolic nitrite, yield [Fe₄S₃(NO)₇]^?. This anion, [Fe₄S₃(NO)₇]^?, reacts with sulphur to give the cubane-like [Fe₄S₄(NO)₄]: the synthesis of its selenium analogue, [Fe₄Se₃(NO)₇]^? is described. The complexes [Fe₂(SR)₂(NO)₄] (R = Me, Et, Prⁿ, Prⁱ, Bu^t, PhCH₂) all consist of two isomers in solution, presumed to have structures of C_2h and C_2v, symmetry: activation parameters for the C_2h?C_2v reaction are reported.     

NMR study of intramolecular processes in EDTA metal complexes

The kinetics of the intramolecular acetate scramblings occurring in thirteen ethylenediaminetetraacetate (EDTA) complexes has been studied by analyzing the modification observed in the NMR spectra of their D₂O solutions, when temperature is changed. The experimental results indicate that the Δ, Λ conversion is a fast process on the NMR time scale for each of the complexes considered, whereas the nitrogen inversion occurs at an observable rate in the case of the Cd(II), In(III), Sc(III), Y(III) and Lu(III) chelates and is too rapid in the other complexes. Computer analysis of the experimental NMR spectra has been performed in order to obtain enthalpy, entropy and free energy of activation concerning the N inversion of the cited chelates. Twist and bond breaking mechanisms are discussed with reference to both scrambling processes.     

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.     

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)     

Electronic structure and reactivity of ylidic systems : V. Ylid structure information form NMR data

Bond systems in triphenylphosphorus ylids, methylenetrimethylphosphorane and their tricarbonylnickel salts are discussed by interpretation of ¹³C NMR results.     

NMR studies of mixed-ligand iron(III) dithiocarbamates

¹H NMR studies of mixed-ligand iron (III) dithiocarbamates have been carried out using the following ligands: N,N-diethyldithiocarbamate, morpholinyl-N-, and piperidyl-N-carbodithioate. The ligand exchange equilibria gave all species of the general formula Fe(dtc)_n(dtc′)_3?n, where n = 0-3 with nearly random statistical distribution of Fe(Et₂dtc)_n(morphdtc)_3?n complexes. Magnetic moments of the mixed-ligand complexes have been determined. Both the magnetic moment and isotropic shift temperature dependences confirmed the cross-over properties of these mixed-ligand complexes.     

Structural studies of sialon ceramics by high-resolution solid-state NMR

High-resolution solide-state ²⁷Al NMR with magic-angle spinning (MASNMR) readily monitors the quantity and coordination (four- and six-fold) of aluminium in two ceramic materials of the SiAlON system. Sialon X-phase, of approximate composition Si₃Al₆O₁₂N₂, contains aluminium-centred octahedra and tetrahedra in the ratio ca. 1.9:1.0, while another sample containing a mixture of sialon polytypoids shows AlO₆ octahedra and a large quantity of what is most probably nitrogen-coordinated tetrahedral aluminium. In addition, ²⁹Si MASNMR detects two different kinds of silicon in the latter sample in a 2:1 ratio. These observations are interpreted satisfactorily in terms of the crystal structures of the compounds and provide further examples of the potential of MASNMR in the investigation of complex ceramic systems.     

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.     

Activation of CH bonds by transition metals : V. A study of the mechanism of metallation reactions of benzyl- and meta-fluorobenzylphosphines with RhI,IrI, PdII and PtII compounds

Reaction of R₂PCH₂C₆H₅ (R = cyclohexyl or t-butyl) with [(COT)₂RhCl]₂, [(COT)₂IrCl]₂, PdCl₂ or PtCl₂(benzonitrile)₂ yields cyclometallated compounds. The reactivity appears to decrease in the order Ir^I ρ Rh^I ρ ρ Pd^II ≈ Pt^II, suggesting a different reaction mechanism for univalent and bivalent d⁸ metal atoms. Reaction of meta-FC₆H₄CH₂PR₂ with the same metal chlorides shows that for Rh^I and Ir^I a nucleophilic mechanism operates and for Pd^II an electrophilic one. For Pt^II no decision could be made on the basis of these experiments. Steric effects have a large influence on the rates of the reactions.     

NMR study of extracted compounds of trioctylalkylammonium with rare earth nitrates

¹H and ¹³C NMR was used to investigate the structure of ion pairs formed by trioctylalkylammonium (alkyl = CH₃-C₈H₁₇) cation and rare earth-containing anions in nitrobenzene. The cation-anion distance in the investigated compounds increases from trioctylmethyl to trioctylbutylammonium salt, remaining constant with further growth of the n-alkyl chain. The ion pair formation changes the conformation equilibrium of the cation alkyl radicals to make easier the cation-counter-ion contact.     

Nitrosolates and related compounds—IX: Coordination compounds of divalent copper,nickel and cobalt with nitroacetate(2−) ions as chelating ligands. Crystal and molecular structure of potassium bis[nitroacetato(2−)]cuprate(II)-water (1/1)

The syntheses of K₂[Cu(nac)₂]·H₂O (4), [Cu(nac)(N-N)(H₂O)]·H₂O (N-N = bpy, phen; 5,6) and [M(nac)(N-N)₂]·xH₂O (M = Ni, Co; 7–10) with nitroacetate(2?) ions (nac^2?) as chelating ligands are described.The structure of 4 has been determined by single crystal X-ray diffraction and contains square planar [Cu(nac)₂]^2? units in which the nitro and carboxyl groups of the two chelate ligands are in cis positions. Two of the units form a centrosymmetric dimer with a four-membered CuOCu“O”-ring, the dimers being connected by exo-oxygens of the ligands into two-dimensional layers. The water molecules and the potassium ions are arranged between the layers; there are two kinds of potassium ions with distorted (1+4+1) and (2+4+3) coordinations respectively.