The synthesis of a cationic ylide complex of platinum(II) by the reaction of tetrakis(triphenylphosphine)platinum(O) with choloroiodomethane.

The reaction of Pt(PPh₃)₄ with CH₂Cl1 in benzene yields the cationic ylide complex $\text{cis}$-[Pt(PPh₃)₂(CH₂PPh₃)Cl]I in high yield. This complex has been converted to $\text{cis}$-[(PPh₃)₂(CH₂PPh₃)X]X (X  Br or I) by reaction with LiBr or NaI. Reaction of $\text{cis}$-[Pt(PPH₃)I]I with iodine yields $\text{cis}$-[Pt(PPh₃)₂(CH₂PPh₃)I]I₃. Nmr data are given in support of the suggested structures.     

The structure of nitratotriphenylstannyltin(II): A compound with a tin(IV)tin(II) bond

A compound of formula [Sn^II(NO₃) [(C₆H₅)₃ Sn^IV], containing a tin(IV)tin(II) bond, has been prepared, and its crystal structure is determined.     

Palladium(II) complexes with sulfur ylides: A new complex containing methylsulfoxonium dimethylide as a chelating ligand

The complex [CH₃SO(CH₂)₂·PdI]₂ which contains the new methylsulfoxonium dimethylide as a chelating ligand, is described.     

Thermochemical study of the stepwise protonation of 1,10-diaza-4,7-dithiadecane,and its complex formation with copper(II) and nickel(II) ions in aqueous solution

The behaviour of 1,10-diaza-4,7-dithiadecane (2,2,2-NSSN) in aqueous solution in equilibria with protons, Cu²⁺ or Ni²⁺ ions has been investigated potentiometrically and calorimetrically. The protonation constants for the ligand, and the stability constants for its complexes at 25°C in 0.5 mole dm^?3 (K)NO₃ are reported, together with the corresponding thermodynamic parameters ΔG, ΔH and ΔS. The results are compared with those for 1-aza-4-thiapentane and 1,7-diaza-4-thiaheptane. The ligand 2,2,2-NSSN forms complexes of formula ML²⁺ and MHL³⁺ with both Cu²⁺ and Ni²⁺. It is found that in the non-protonated 1:1 complexes the ligand acts as a tetradentate. In the CuHL³⁺ complex, the ligand is bound through one nitrogen and two sulphur donors, whereas in the NiHL³⁺ complex the ligand is probably bound through only one nitrogen and one sulphur donor. Explanations are suggested.     

Preparation and electronic spectra of some alkyl- and aryl(2,2′-bipyridine)platinum(II) complexes

A series of alkyl- and aryl-(2,2′-bipyridine)-platinum (II) complexes has been prepared by displacement of the diene ligand in the corresponding cyclooctadiene complexes with 2,2′-bipyridine. Dimethyl(1,10-phenanthroline)platinum(II) was prepared in an analogous way. The electronic spectra of the complexes contain metal to ligand charge transfer bands whose energy is dependent on the nature of the substituents on platinum and on the solvent. It is suggested that π-bonding is important in the phenyl—platinum bond.     

A thermodynamic and spectrophotometric study of the complex formation of copper(II) ions with sulphide-containing α,ω-aminopyridines in aqueous solution

The complexation in aqueous solution of ligands of the type

(CH₂)_n?1 S(CH₂)_mNH₂ (n and m = 2 or 3) with Cu(II) has been investigated. The thermodynamic functions ΔG, ΔH and ΔS of complex formation have been determined at 25°C in 0.5 M KNO₃ solution by means of potentiometric and direct calorimetric titrations. They revealed that the ligands studied act as tridentates towards Cu(II).It was found that the CuL²⁺ complexes having one or two six-membered chelate rings are more distorted than their analogues with only five-membered chelate rings.The CuL²⁺₂ complex with L =

CH₂SCH₂CH₂NH₂ was found to be a strong covalent complex, in which both ligand molecules were completely coordinated.     

Cleavage of the carbon-silicon bonds in trimethylsilylacetylenes by trans[(PR3)2PtX(R′OH)]PF6 cations and formation of cationic alkoxycarbene complexes of platinum(II)

Cationic alkoxycarbene complexes of platinum(II) have been isolated in the reactions of trans-[(PR₃)₂PtX(R′OH)]PF₆ (X  H or Me; R′  Me or Et) with Me₃SiCCR′′ (R′′  H, Me or SiMe₃). In these reactions cleavage of the carbon-silicon bond by the nucleophilic attack of alcohol has been observed. These carbene complexes have been characterized by elemental analyses and by IR, ¹H and ¹³C NMR spectral data. ¹³C NMR chemical shift data for carbene carbon atoms suggest that the carbene carbon may be very positively charged.     

Spectrophotometric study of the copper(II)-2,2′-dipyridyl-2-pyridylhydrazone complex formation

The reaction of copper(II) ions with 2,2′-dipyridyl-2-pyridylhydrazone (DPPH) has been studied. Two copper complexes were found to be formed. One at pH 6.5 to 8.5 and the other at pH 11.9 to 12.6 with molecular extinction coefficients of 1.9 × 10⁴M^?1 · cm^?1 at the absorption maximum of 478 nm and 3.8 × 10⁴M^?1 · cm^?1 at 448 nm, respectively. A sensitive spectrophotometric procedure for the determination of copper at less than a 1-ppm level is proposed.     

Thermal and chromatographic behaviour of metal complexes. Part II. Complexes of platinum(II) with dipeptide ester

Experimental measurements of the rate of reduction of particles of Carol Lake and Kiruna ores have been made using pure hydrogen and pure carbon monoxide and mixtures of these two gases. The temperature range covered was 773–1143 K and throughout this range the reduction rate with hydrogen was greater than that with carbon monoxide. A retracting core model was found to best fit the experimental data even when granules of 9 × 10^?4 m diameter were used. Reduction with gas mixtures of hydrogen and carbon monoxide give rates intermediate between those of the pure gases.     

Spectrophotometric study of pseudopurpurin-Pd(II) dimer complex. Spectrophotometric determination of traces of Pd(II)

We have studied spectrophotometrically the Pseudopurpurin-Pd(II) complex in an ethanolic-water medium ¦Ethanolamine ¦_optimum = 4 × 10⁻¹M; λ = 670 nm; 20% H₂O; stable for at least 4 hr; ¦Reagent¦_optimum = 5 × 10⁻⁵M; stoichiometry 2:2; log K = 17.7. A new method for the spectrophotometric determination of Pd traces is proposed for concentrations between 0.30 and 2.40 ppm. The relative error and the interferences of the method have been investigated.     

Ligand effects on the Pt(II) → Pt(0) reduction of dichlorobis(tertiary phosphine)platinum(II) complexes: Correlations between electrochemical data,spectroscopic data,and electronic ligand parameters

Cyclic voltammetry has been employed to study the diffusive, irreversible platinum(II) → platinum(0) reduction of three sets of structurally related complexes: cis-[PtCl₂P{p-C₆H₄X}₃)₂] (X = H, CH₃, Cl, F, OCH₃, N(CH₃)₂); cis-[PtCl₂(PPh₂R)₂] (R = CH₃, n-C₃H₇, n-C₅H₁₁, n-C₆H₁₃, n-C₁₂H₂₅) and cis-[PtCl₂(PR₃)₂] (R = CH₃, C₂H₅, CH₂ch₂CN). Relationships between the peak potentials for the Pt(II) → Pt(0) reduction and thermodynamic parameters which measure the electronic properties of the ligands are shown to exist for complexes of P{p-C₆H₄X}₃ ligands, implying a thermodynamic origin for the sensitivity of the peak potentials to structural change. Complexes of both P{p-C₆H₄X}₃ and PPh₂R ligands show correlations between peak potentials for reduction and the ³¹P{¹H} NMR spectroscopic parameter, ¹J(¹⁹⁵Pt, ³¹P). Correlations with values of δ(³¹P) exist in both cases, but a correlation with the coordination chemical shift, Δδ(³¹P), exists for complexes of PPh₂R, and not for complexes of P{C₆H₄X}₃. Complexes of PR₃ ligands show no correlation between the peak potentials measured for the Pt(II) → Pt(0) reduction and electronic or spectroscopic parameters, except possibly ¹J(¹⁹⁵Pt, ³¹P).     

Synthesis and molecular structure of hydrido(tetrahydroborato)(1,1,1-tris(diphenylphosphinomethyl)ethane)-iron(II)

Sodium tetrahydroborate reacts with iron(II) tetrafluoroborate and 1,1,1-tris(diphenylphosphinomethyl)ethane (triphos) to give the complex (triphos)-FeH(BH₄) whose molecular structure, determined from X-ray data consists of monomolecular units in which the iron atom is six-coordinated by the three phosphorus atoms of the ligand, two hydrogen atoms of the BH₄ group, and a hydridic hydrogen atom. Variable temperature ³¹P NMR spectra reveal stereochemical non-rigidity of the complex in solution.     

Electrochemical phase formation (ECPF) and macrogrowth Part II. Two-rate models

A general theory is evolved for a class of macrogrowth models which possess two independent growth-rates. Relations connecting growth-rates to growth geometry are established and some new growth forms are shown to result for models with passivation or diffusion-controlled rates. The corresponding potentiostatic responses, their small and large time behaviours and peak characteristics are obtained. Numerical transients are also presented. An empirical equation is derived as a special case and an earlier equation is corrected. An interesting stochastic result pertaining to nucleation events in the successive layers is proved.     

The reaction of allene with β-diketonatoiridium(I) complexes: formation and crystal structure of a new bis-β-allylic derivative of iridium(III)

The reaction of allene with (Hfacac)Ir(η-C₈H₁₄)₂ to give a new bis-η-allylic complex of iridium(III) containing an allene tetramer is described; the X-ray structure of this compound is reported.     

1,2- and 1,7-Dicarba-closo-dodecarborane(12)platinum(II) complexes formed through metal—carbon σ bonds: cis- and trans-monohydrido derivatives

New neutral platinum(II) monohydridocarborane complexes of general formula cis- and trans-L₂PtH(σ-carb), where L = (C₂H₅)₃P, (C₆H₅)₃P, (C₆H₅)₂(CH₃)P, (C₆H₅)(CH₃)₂P and carb = 2-R-1,2- or 7-R-1,7-B₁₀C₂H₁₀^? (R = H, CH₃, C₆H₅), have been prepared. The configurations of the complexes obtained have been assigned by ¹H NMR spectroscopy. The _cis-monohydridocarborane complexes here reported are the first examples of neutral _cis-monohydrido derivates of platinum(II) containing platinum—carbon σ bonds. ¹H NMR chemical shifts and coupling constants of the prepared complexes are also reported, and used in a tentative evaluation of the _trans-influence of the carbonage ligands.     

Hydrido Cyanoalkyls of platinum (II)

The preparation and reactions are described of some novel platinum(II) complexes with a hydride ligand group trans to an sp³ carbon, viz. [PtH(YCN)-(PPh₃)₂] with Y  (CH₂)_n (n = 1—3) or o-CH₂C₆H₄.     

Study of platinum electrodes by means of electrochemistry and low-energy electron diffraction: Part II. Comparison of the electrochemical activity of Pt(100) and Pt(111) surfaces

Low-energy electron diffraction patterns were obtained for Pt(100), Pt(111) and polycrystalline electrodes before and after exposure to aqueous 1 M H₂SO₄. Linear potential scan voltammograms were recorded. The results demonstrate that one of the principal peaks in the hydrogen region of the current-potential curves of polycrystalline Pt is assignable to Pt(100) and the other to Pt(111). The maximum amount of chemisorbed hydrogen corresponds to one hydrogen atom per surface Pt atom. The Pt(100)[1×1], Pt(111) and polycrystalline surfaces appear to withstand prolonged voltammetric characterization at potentials between ?0.2 and 1.2 V vs. a calomel reference. Variation of the voltammetric characteristics of hydrogen chemisorption with changes in the nature of the supporting electrolyte anion are described.     

Kinetics of the thermal dehydration of trans-fluoroaquobis(ethylenediamine)chromium(III) tetracyanometallate(II) [metal(II) = Ni(II), Pd(II) and Pt(II)]

The solid phase thermal deaquation—anation of trans-[CrF(H₂O)(en)₂][M(CN)₄] (M = Ni, Pd, Pt; en = ethylenediamine) has been investigated by means of non-isothermal DSC and isothermal and non-isothermal TG measurements. The physical model for these reactions (nucleation, growth, diffusion or intermediates) has been found by comparison of the isothermal and non-isothermal TG data for all the principal g(α) expressions (0.2?α?0.8) and by the shape of the isothermal curves. The values found for activation energy are low (～ 130 kJ mol^?1 for the Ni compound, ～ 140 kJ mol^?1 for the Pd compound, and ～ 100 kJ mol^?1 for the Pt compound). These data permit the assignment of the deaquation—anation mechanism of the S_N1 type involving a square-base pyramid activated complex and elimination of water as Frenkel defects.     

Paramagnetic ion binding to amino acids,structural and dynamical information on a Mn(II) complex of L-proline from 13C relaxation data

The ¹³C relaxation times (T₁ and T₂) and isotropic contact shift (Δω) of 1.28 molar aqueous solutions of L-Proline at pH = 11 (or pD = 11.4) containing 10^?4 - 10^?5 M manganese perchlorate are measured at 62.86 MHz over a temperature range of 28–80°C. Under these conditions, the Mn²⁺ cation is bound to three L-Proline molecules in their dibasic form, and a fast exchange is occurring between bound and bulk L-Proline molecules. The longitudinal relaxation of carbons α, β, γ, δ of L-Proline molecules in this complex is shown to be purely dipolar, and is controlled by the rotational reorientation of the complex. The transverse relaxation of bound L-Proline molecules is mainly scalar and is controlled by the electronic relaxation. Overall relaxation rates and paramagnetic shifts also depend on the ligand exchange rate k_M (from bound to free sites) at lower temperatures. The measurement of these quantities allow us to determine (i) the structure of the complex: the Mn(II) cation may be positioned with respect to each proline ligand, the sites of coordination are the unchanged nitrogen and one carboxylic atom, the distance to the Mn²⁺ cation are respectively 2.08 and 1.97 Å; (ii) Hyperfine coupling constants: A= + 0.16; 0.08; 0.25 and 0.22 MHz for carbons α, β, γ, δ, respectively. (iii) Electronic relaxation parameters: assuming that T_1e ( = 2.18 x 10^?8 s at 25°C) is controlled by the modulation of the quadratic crystalline zero-field splitting interaction allows us to estimate the trace of the corresponding tensor: Δ = 0.0305 cm^?1, and a correlation time τν(25°C) = 1.32 ps for the impact of solvent molecules against the Mn²⁺-L-Proline complex (iv) Kinetic parameters for ligand exchange: k_M(25°C) = 7.41 x 10⁴s^?1; ΔH³ = 15.6 kcal.mol.^?1; ΔS³ = 16.1 e.u.