Pulsed fourier transform NMR of substituted aryltrimethyltin derivatives : II. (119Sn-13C) coupling constants and 13C chemical shifts of meta- and para-derivatives

Carbon-13 NMR data are reported for thirteen para- and meta-substituted phenyltrimethyltin compounds, RC₆H₄Sn(CH₃)₃, where R = para-N(CH₃)₂, para-OCH₃, para-OC₂H₅, para-CH₃, meta-CH₃, -H, para-F, meta-OCH₃, para-Cl, para-Br, meta-F, meta-Cl and para-Sn(CH₃)₃. In the para-derivatives, correlation coefficients with Hammet σ-constants of greater than ca. 0.9 are obtained with the tin-carbon couplings to methyl, C₁ and C₄ carbons, and with the carbon-13 chemical shifts δ(C(1)). In the meta-derivatives, the couplings |J(Sn-CH₃)|:, |:J(Sn-C(1))|:, |:J(Sn-C(3))|: and |:J(Sn-C(6))|:, and the shifts δ(C(1)) and δ(C(5)) correlate well with Hammett σ. In the para-derivatives, sensitivity to change in substituent falls off C(4) > C(3, 5) > C(1) > C(2, 6) > CH₃ as registered by the δ(C), while in the meta-derivatives δ(C) changes decrease C(3) > C(2), C(4) > C(1) > C(5), C(6) > CH₃. The magnitudes of the tin coupling constants decrease C(1) > CH₃ > C(3, 5) > C(2, 6) > C(4) in the para-derivatives, while in the meta-series the order is C(1) > CH₃ > C(3), C(5) > C(2) > C(6) > C(4). The two sets of one-bond |:J(Sn-CH₃)|: and |:J(Sn-C(1)|: values correspond closely to the 0.25/0.33 ratio of coefficients in the LCAO approach, and are interpreted in terms of s-electron redistributions at the tin atom with change in substituent.     

Structural studies in main group chemistry III. Tin-119m mössbauer investigation of some tin-nitrogen bonded compounds

The tin-119m Mössbauer data are presented for several classes of organotin- nitrogen bonded compounds, including N-stannylamines, -imines, -amides, and -carbamates. Thc structures of the N,O-bis(trialkylstannyl)carbamates are discussed. Those derivatives possessing the Sn-NR-C(O)X group are intermolecularly associated via carbonyl→tin coordination, the strength of the coordination varying with X in the manner H ≈ OSnR₃ > OR.     

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.     

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)     

Synthesis and spectroscopic studies on organotin derivatives of biologically active Schiff bases

Some five- and six-coordinated di- and tri-n-butyl tin(IV) complexes of the type Bu₂SnL, Bu₂SnL₂ and Bu₃SnL (where L is the anion of a monofunctional bidentate or bifunctional tridentate Schiff base) have been synthesized and characterised on the basis of microanalyses, molecular weight determinations, IR, NMR (¹H, ¹³C, ¹¹⁹Sn) and ¹¹⁹Sn Mössbauer spectroscopy. These complexes are highly active towards bacteria.     

Multinuclear magnetic resonance and related studies on some organotin(IV) complexes of dithiocarbazates

Synthesis, characterization and geometrical features of pentacoordinated dibutyltin(IV) dithiocarbazate complexes of the type n-Bu₂Sn L (where L = dianion of $\text{S}$-methyl-B-N (2-hydroxy-phenyl) methylene and methyl dithiocarbazate are described. These are obtained as viscous oils from the reactions of n-Bu₂SnO with equimolar proportions of the ligands in benzene. On the basis of UV, IR, NMR (¹H, ¹³C, ¹¹⁹Sn) spectra along with the mass spectral fragmentation pattern a trigonal bipyramidal geometry is proposed. The N atom probably occupies the axial site, while the remaining two donor atoms O and S and the dibutyl groups rest in an equatorial plane. These complexes are active against P.388 Lymphocyte leukaemia system.     

Vibrational spectroscopy of solids under high pressures. Part I. Raman spectra of inorganic hexafluorometallate compounds

Raman spectra of a series of isomorphous hexafluorometallates (TlSbF₆; BaMF₆, M = Si, Ge, Sn, and Ti, space group $\text{R}\text{3}\text{m-D}{}^5{}_{\mathrm{3d}}\text{, Z = 1}$) have been measured under high pressures up to 25 kbar with a new opposed sapphire anvil cell. Pressure calibration has been achieved by means of the R₁ fluorescence band of ruby. The frequency of the only Raman active lattice mode (libration of the octahedral anion) of each compound shows a higher pressure dependence than do the internal vibrations of the anions. The E_g components of the ν₅ modes of the MF₆ octahedra which are coupled to the E_g lattice modes because of their same symmetries and small frequency differences exhibit higher pressure sensitivities than do the uncoupled internal modes. These findings may be used as a further means for symmetry assignment. BaGeF₆ undergoes a reversible phase transition at 9.6 kbar; the split librational modes of the high-pressure phase show the highest pressure dependences of up to about 3 cm^?1 · kbar^?1 found in this investigation.     

Fourier transform heteronuclear magnetic triple resonance in complex spin systems—III: Symmetrical ditertiary phosphine complexes of group VI metal carbonyls

Magnetic multiple resonance experiments of the types ¹³C-{³¹P, ¹H}, ¹³C{¹H} and ³¹P{¹⁸³W, ¹H} have been used to determine the magnitudes and signs of PC and PP coupling constants in the symmetrical complexes LM(CO)₄ (L = Ph₂P(CH₂)_nPPh₂, Ph₂PN(H)PPh₂, (Ph₂P)₂CCH₂, cis-Ph₂PCHCHPPh₂; M = Cr, Mo, W; n = 1–4). A knowledge of the signs of the couplings shows that they display a systematic pattern of behaviour according to metal atom and ring size and this may have diagnostic value. ¹³C, ³¹P and ¹⁸³W chemical shifts are also reported.     

The chemistry of hetero-allene and -allylic derivatives with rhodium : I. The reactions of rhodium(I)-hetero-allylic compounds with hetero-allenes; B. Carbon Disulfide

The rhodium(I) complexes Rh[X-C(Z)-Y] (PPh₃)₂, in which [X-C(Z)-Y] represents an uninegative unsaturated heteroallylic bidentate ligand, coordinating via two of the three hetero atoms (X, Y, Z  P, S or N), react at elevated temperature with an excess of the hetero-allene SCS to give the rhodium(I)-thiocarbonyl complexes Rh[X-C(Z)-Z](CS)(PPh₃). In the initial step a first CS₂ molecule is coordinated side-on by one of the CS double bands. Subsequent reactions can be blocked at this stage by addition of pyridine, resulting in RhCl(η²-CS₂)(PPh₃)(py)₂. The formation of the CS complexes occurs in two ways. Either by direct sulfur abstraction from the Rh^I(η²-CS₂) complex by PPh₃ or by a dimerisation of two CS₂ molecules and elimination of a CS moiety, resulting in a Rh^III-thiocarbonyl-trithiocarbonato complex, immediately followed by demolition of the trithiocarbonato-CS^?2₃ fragment, by PPh₃ to SPPh₃ and CS₂.Complexes containing a CS^?2₃ fragment, but no CS moiety, can also be identified by IR measurements. These products may be formed in a sidereaction upon elimination of CS.     

Ylid complexes of organotin and -lead halides

Carbonyl-stabilised ylids form complexes of varying stoichiometries with organotin and -lead halides     

Ligand effects on the redox potentials of metal carbonyls : Relationship to co force constants in manganese(I) derivatives

The reversible oxidation potentials E^o of a single series of methylcyclopentadienyldicarbonylmanganese(I) derivatives η⁵-MeCpMn(CO)₂L are measured for a wide variety of ligand types, including L = alkyl and aromatic amines, alkyl cyanide and isocyanide, alkene, alkyl and aryl phosphines and phosphites. The relationship of E^o with the carbonyl force constants evaluated by the Cotton-Kraihanzel method is presented.     

ICP argon emission in the near infrared 1–2μm by high resolution Fourier transform spectrometry

The emission characteristics of the inductively coupled plasma in the near infrared spectral region from 0.9 to 2.0μm have been recorded by high resolution Fourier transform spectrometry. This region contains many strong atomic argon lines. The 109 lines with signal-to-noise ratio greater than four in the observed spectrum are identified and reported here with wavenumber accuracy on the order of 0.001 cm^?1. Also reported are relative intensities and line widths. This information is useful for determining spectral interferences to be expected in the development of analytical applications for the ICP in the near infrared.     

Theoretical study of the static Jahn-Teller effect—I. Two-mode vibronic coupling in octahedral halocomplexes with doubly degenerate electronic states

A two-mode E_g-(a_1g+e_g) vibronic coupling is analyzed for octahedral systems. Analytic formula for the adiabatic potential surface (APS) is obtained considering quadratic vibronic terms and anharmonicities of normal vibrations as well. Potential constants, viz. five elastic force constants and three vibronic constants, are evaluated from the numerical map of the APS applying the non-linear regression analysis. Numerical values are obtained for hexahalocomplexes on the CNDO/INDO level of total energy calculations.     

COS and C3S2: The discovery and chemistry of two important inorganic sulfur compounds

Although CO and CO₂ have been known since the dawn of chemistry and although CS₂ was discovered as early as 1796,¹ COS and C₃S₂ were not discovered until 1867 and 1893, respectively. This article considers the circumstances surrounding their discoveries as well as later reports on their chemistries. Both compounds were first prepared by Hungarian chemists, and both are of great theoretical and practical importance. The discovery and preparation of COS by Károly (Karl) Than is a beautiful example of logical chemical thinking, whereas the serendipitous discovery of C₃S₂ by Béla Lengyel is a case study in careful experimentation and keen observation. The sesquicentennial anniversary of the birth of Than, who is regarded as the founder of modern Hungarian chemistry, makes this article of timely significance. Since both he and his student Lengyel and their accomplishments have been neglected by English-speaking chemists and historians of chemistry, they are briefly discussed in this article.     

Thermal studies on tetrazole derivatives using a differential scanning calorimeter. I

The thermal decomposition of arylidene tetrazolyl hydrazones has been studied under dynamic and isothermal conditions using a differential scanning calorimeter. Attempts have been made to evaluate the thermochemical and kinetic parameters of these compounds. It has been observed that the thermal stability of the tetrazole derivatives decreases with increasing substitution of nitro groups in the aromatic ring.     

Complex formation of 1,4,7,10-tetraoxacyclododecane with alkali metal ions studied by 13C spectroscopy

Complex formation of 1,4,7,10-tetraoxacyclododecane (12-crown-4) with lithium, sodium and potassium salts in methanol solution was investigated. The strong influence of complexing on the chemical shift of the single ¹³C NMR line permitted titration of the ligand with alkali metal salts. Concentration stability constants of the complexes were obtained by a computerized iterative least squares method. Na⁺ and K⁺ form both 1: 1 and 1: 2 complexes, log K₁ = 2.1 and log K₂ = 3.8, log K₁ = 1.7 and log K₂ = 2.4 respectively. Li⁺ is complexed weakly. Assuming 1: 1 stoichiometry the complex stability constant is estimated to be < 1.     

The polarography of oximes: I. 9,10-Phenanthraquinone monoxime

Polarography of 9,10-phenanthraquinone monoxime has been carried out in buffers (pH 3.50 to 13.40) of constant ionic strength 0.5 M in 40% alcoholic solutions at 35 ± 0.5 °C. The oxime group underwent diffusion-controlled reduction (4e) over the whole pH range studied. The number of electrons involved in the reduction was found coulometrically as well as by incorporating the value of the diffusion coefficient, obtained by using a McBain-Dawson cell, into the Ilkovic equation. Controlled potential electrolyses and uv spectroscopic methods were used to identify the products. Koutecky's method was used to compute the kinetic parameters (αn_aand ?log k_f,h^o) for the reduction of the oxime group and reduction mechanisms are proposed.     

Optical activity of compounds formed by aminocomplexes of Co(III) and carbohydrates—I

The preparation of aminocomplexes of Co(III) containing d-ribose, l-sorbose or d-glucosamine as second ligand is described. Their spectral features and optical activity are reported. Formation in solution of complex species with other chosen carbohydrates gives ground for discussion as to the origin and sign of the observed Cotton effects.     

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.