Cumulated double bond systems as ligands : IV. 1H and 13C NMR studies of the intra- and inter-molecular exchange processes of cationic dialkylsulfurdiimine compounds of RhI,IrI and PtII

The preparation and properties are described of trans-[(Ph₃P)₂(CO)M(RNSNR)] [ClO₄] (M  Rh^I, Ir^I; R  Me, Et, i-Pr, t-Bu) and of cis- or trans-[L₂Pt(RNSNR)X] [ClO₄] (X  Cl^?, L  Et₂S, PhMe₂As, PhMe₂P, R  Me, t-Bu; X  CH₃, L  PhMe₂P, R  Me).¹H and ¹³C NMR data show the existence of various isomers in solution which may interconvert via intra- and inter-molecular exchange processes. A general reaction scheme for the intramolecular exchange processes is discussed.     

Relative olefin—metal bond strengths in some platinum (O) compounds

Measurements are reported for the enthalphy of the reaction L₂Pt(c)+nCS₂(l) → L₂PtCS₂(soln)+olefin(soln)+(n-1)CS₂(1) where L is triphenylphosphine, and the olefins used were ethylene, phenylethylene, and cis- and trans-1,2-diphenylethylene. These enthalphies, when combined with othe data, lead to the conclusion that the relative strengths of the platinum—olefin bonds decrease in the order: trans-1,2-diphenylethylene >cis-1,2-bisphenylethylene > phenyl-ethylene > ethylene.The difference between the cis and trans compounds is relatively small. The above order is in agreement with qualitative observations on the relative stabilities of these compounds.     

Reactions of platinum complexes with spiro compounds. formation of platinospiroalkanes

Spiro[2.nalkanes (n = 2, 4, 5) react with platinum complexes to form compounds of composition PtCl₂(spiroalkane). These materials have been characterized by infrared and nuclear magnetic resonance spectra, and the point of insertion has been shown to be the cyclopropyl carbon—carbon bond opposite the spiro carbon.     

MetalAzo and metalimine compounds : III. The influence of metal basicity on the cleavage of C:H bonds by RhI and IrI

From the reaction of R′X=NR (X = N or CH) with [MCl(C₈H₁₄)_2| in the presence of CO or PR₃. σ(_N)- coordinated complexes cis-RhCl(CO)₂(R′CH=NR) and cyclometallated complexes MHCl(L′)(PR₃)₂ [′ is cyclometallated R′X=NR; R = Ph or Cy when M = Ir; R = Cy when M = Rh] were isolated.The ease of CH bond breaking by M¹ appears to be strongly dependent on the basic properties of M_I, and decreases as follows: aromatic CH > olefinic CH > aliphatic CH. On the basis of the chemical and structural information, the metallation can be explained in terms of Pearson's symmetry rules for chemical reactions.For the cyclometallated azo compounds, ν(N=N) shows resonance enhancement ion the Raman spectra, and appears to be very sensitive to the basicity of M^I in the reactant system.     

η2-dithiomethyliron(II) ionic complexes. Evidence for a strong dependence on the nature of the trans-phosphorus ligands bonded to iron

Cationic η²-dithiomethyliron(II) complexes have been made by alkylation of the uncoordinated sulfur atom of Fe(CO)₂[η²-CS₂](L)₂. Surprisingly, only when the phosphorus ligands L are strong donors (PMe₃, PMe₂Ph) does coordination of iodide take place to give the neutral Fe(η²-CS₂CH₃)(I)(CO)(L)₂ derivatives. The ¹³C NMR spectra of the latter at 215 K indicated the presence of both isomers when L was PMe₂Ph. Reaction with iodine under carbon monoxide regenerated the cationic precursor.     

Studies on double selenates. I. Thermal decomposition of lanthanum and alkali metal double selenates

Thermogravimetry, differential thermal analysis and other methods of analysis have been used to study the decomposition of hydrated lanthanum and alkali metal double selenates up to 1300°C. The results showed slight variations in the initial temperature of the various intermediate decomposition stages of the double selenates, as compared with the initial temperature of the corresponding decomposition of the simple selenates. The results also permitted the suggestion of mechanisms of thermal decomposition of these compounds.     

Room-temperature fluorescence spectrometry of some pharmaceutical compounds

Room-temperature fluorescence of 66 pharmaceutical drugs are presented using a mixture of ethanol/water as solvent. The analytical figures of merit for the fluorescent species are reported with limits of detection ranging between 1 and 30 ng/ml for most of them and with average blank standard deviation of 7.6%. The spectral band half-widths are also reported.     

Diazabutadienes as σ,π-bridging ligands in binuclear molybdenum carbonyl complexes containing molybdenummolybdenum double bonds

Reduction of Mo(CO)₄ DAB (DAB = diazabutadiene) followed by oxidation with Mn(CO)₃BrDAB or HCl gives a small yield (15 to 25%) of complexes of the type Mo₂(CO)₆(DAB)₂, in which the two DAB ligands bridge a molybdenummolybdenum double bond and act as σ,π-donors.     

Transition metal-catalyzed syntheses of organic acids by chelation-promoted regioselective double bond insertion

The rhodium- or nickel-catalyzed reaction of vinylic halides with alkali salts of 3-butenoic acids leads to regioselective formation of dienoic acids, containing 3,5-conjugated double bonds. Monoarylacetylenes also react with 3-butenoic acids in a rhodium-catalyzed synthesis of the same acids. The stereochemistries of the acids and the nature of the by-products are discussed in the light of the proposed mechanisms.     

Nitrato(triphenylphosphine) complexes of the platinum metals; Detection of triphenylphosphine oxide ligands

Reactions of some platinum group metal triphenylphosphine complexes with nitric acid afford nitrato(triphenylphosphine) derivatives in good yield; the complex “Rh(NO₃) (NO)₂(OPPh₃)₂” is positively identified as [Rh(NO₃)₂ (NO) (PPh₃)₂]     

The thermal properties of inorganic compounds: II. Evolved gas studies of some mercury(I) and (II) compounds

The combined thermal analysis techniques of thermogravimetry, evolved gas analysis and mass spectrometry were used to investigate the thermal decomposition of several selected mercury(I), (II) compounds. Although TG curves are presented, the analysis of the evolved gases formed during the thermal decomposition processes was of greater interest. Gaseous products detected included: HgSO₄SO, SO₂ and O₂; Hg(SCN)₂CS₂, (CN)₂ and N₂; Hg(NO₃)₂NO, N₂O, NO₂ and O₂; HgNO₃ H₂ONO, NO₂ and N₂O; and Hg(C₂H₃O₂)₂—organic fragments. The evolved gas analysis was complicated by sublimation of the compounds at low pressures.     

Hydridocyanoalkyl complexes of platinum(II). Insertion of olefins into the PtH bond

The preparation and spectroscopic properties are described of some platinum(II) complexes having a hydride ligand cis or trans to an sp³ carbon, viz. trans-PtH(YCN)(PPh₃)₂ and cis-PtH(YCN)(LL) with YCN = C₂H₄CN, n-C₃H₆CN, o-CH₂C₆H₄CN and LL = bis(diphenylphosphino)-ethene or -ethane. The complexes trans-PtH(YCN)(PPh₃)₂ can add a fifth ligand in solution; the resulting five-coordinate complex was observed by ³¹P NMR in the case of PtH(C₃H₆CN)(PPh₃)₃. Insertion of olefin (ethen, 1-cyanoethene, norbornadiene, allen) into the PtH bond of the trans-hydrido complexes occurs to give cis-dialkyl complexes, but the cis-hydrido complexes are unreactive. The mechanism of insertion is discussed in terms of the kinetics and the geometries of reactants and products.     

Stereochemistry of reactions in the 1,2-dimethylsilacyclopentane ring systems. I. Stereospecific transformations

Preparations, separations of geometric isomers, and structural assignments based on nmr and on chemical evidence are described for a number of 1-substituted 1,2-dimethylsilacyclopentanes. A number of stereospecific reactions have been observed, and the stereochemistry is in all cases the same as that observed for acyclic silanes. A discussion of the role of ring strain in determining stereochemical outcome and reaction rates is presented.     

A.c. polarographic determination of polyethylene glycols — application to analysis of photographic processing solutions

The tensammetric behaviour of several polyethylene glycol (PEG) molecules is described. At neutral pH, PEG gives both a positive and a negative peak. At high pH the positive peak is obscured by the anodic dissolution of mercury and at low pH the negative peak is obscured by the hydrogen evolution reaction. Tensammetry is shown to be applicable to the direct determination of PEG in photographic processing solutions. Despite the complex chemical composition of these solutions the only pre-treatment required was dilution of samples.     

Rhodium(I) phosphine complexes containing bidentate unsaturated thio ligands: II. Reactions with O2 and H2

The rhodium(I) complexes (Ph₃P)₂Rh[Me₂NC(S)NC(S)NMe₂], (Ph₃P)₂Rh[SC(S)NMe₂] and (Ph₃P)₂Rh[PhNC(S)NMe₂] react with O₂ to give 1/1 dioxygen adducts. In solution, trans-(Ph₃P)₂Rh(O₂)[Me₂NC(S)NC(S)NMe₂], cis- and trans-(Ph₃P)₂Rh(O₂)[SC(S)NMe₂] and cis- and trans-(Ph₃P)₂Rh(O₂)[PhNC(S)NMe₂] are observed. For (Ph₃P)₂Rh(O₂)[PhNC(S)NMe₂], there is a solvent effect on the initial cis—trans ratio and the rate of O=PPh₃ formation. In C₆H₆, O=PPh₃ formation from (Ph₃P)₂Rh(O₂)[PhNC(S)NMe₂] is inhibited by additional PPh₃.The reaction of (Ph₃P)₂Rh[Ph₂PC(S)NPh] with O₂ in the presence of additional PPh₃ gives O=PPh₃ and cis-(Ph₃P)₂Rh(O₂)[Ph₂P(O)C(S)NPh] as the only products. The same complex also can be prepared from (Ph₃P)₂Rh[Ph₂P(O)C(S)NPh] and O₂.Only (Ph₃P)₂Rh[PhNC(S)NMe₂] reacts with H₂ at room temperature to give (Ph₃P)₂RhH₂[PhNC(S)NMe₂], which is a catalyst for cyclohexene hydrogenation.     

Non-stoichiometric molybdenum oxides as cathodes for lithium cells: Part I. Primary batteries

Some non-stoichiometric Mo oxides have been tested as cathodes for primary Li cells. Their performance has been evaluated as a function of current density, electrolyte, temperature, cathode porosity and formulation. Specific capacities exceeding 0.4·Ah g^?1 could be reached at low rates. As found with MoO₃, these oxides give rise to the formation of ternary phases of the type Li_myMo_mO_3m?1. Li⁺ insertion in the lattices allows structure retention for Li/Mo ratios lower than 0.7–0.8, whereas higher Li⁺ contents result in the appearance of new phases.     

Antiferromagnetic complexes involving metalmetal bonds : I. Synthesis and molecular structure of an antiferromagnetic dimer with a CrCr bond

The binuclear complex (C₅H₅)₂Cr₂(S)(SCMe₃)₂ was prepared by refluxing a solution of chromocene and t-butylmercaptane in heptane. The structure of the product was determined by single crystal X-ray diffraction. The chronium atoms are linked by a sulphide bridge (SCr 2.24 Å;, <CrSCr 74.1° and two SCMe₃ bridges (CrS 2.38 Å;, <CrSCr 68.3–69.3°). The two cyclopentadienyl ligands (CC 1.41 Å;, CrC 2.23 Å;) are in apical positions, their ring planes being parallel to each other. The complex is an antiferromagnet (?2J cm^?1) despite the small CrSCr angles and short chromiumchromium distance (2.689 Å;) indicative of strong CrCr bonding.