A 29Si, 13C and 1H NMR study of the interaction of various halotrimethylsilanes and trimethylsilyl triflate with dimethyl formamide and acetonitrile,a comment on the nucleophile induced racemisation of halosilanes

The ²⁹Si, ¹³C and ¹H NMR spectra of $\text{1}\text{1}$ mixtures of Me₃SiI and Me₃SiOSO₂CF₃ with DMF in CD₂Cl₂ show signals that are consistent with the formation of Me₃SiO$\text{C}\text{+}$H(NMe₂)X^? but not with penta- or hexa-coordinate silicon species. The spectra of a $\text{1}\text{1}$ mixture of Me₃SiBr and DMF show a rapidly exchanging, equilibrium mixture of Me₃SiO$\text{C}\text{+}$H(NMe₂)Br^? and starting materials. No strong evidence for salt formation between DMF and Me₃SiCl was obtained. The spectra of Me₃SiX (X = I, Br, Cl, OSO₂CF₃) in CD₃CN indicate that neither adduct formation nor extra coordination at silicon is significant.     

Wannier states of molecular impurity in a liquid rare gas

We have measured the vacuum ultraviolet absorption spectra of CH₃I in solid and in liquid krypton in the spectral region 2000–1450 Å. In both phases we have observed two Wannier series n(²E_{$\text{3}\text{2}$}) and n(²E_{$\text{1}\text{2}$}) up to n = 3. Information has been obtained concerning the features of the conduction band in a liquid rare gas.     

On the validity of level crossing calculations for 10B NQDR

The I=3 nuclear quadrupole resonance spectra (e.g. ¹⁰B) present peculiarities in comparison to I=1 or I=$\text{3}\text{2}$ spectra. Hence, the predictions of the simple level crossing theory with regard to the relative line intensities of I=3 DRLC spectra were checked by comparison with the experimental spectrum of borazine (B₃N₃H₆). If the experiment is properly conducted level crossing theory will be able to calculate the relative line intensities correctly in spite of the huge differences in the quantum-mechanical transition probabilities and other complications of the I=3 system. The relative line intensities should be fairly independent of the value of the asymmetry parameter.     

Bis(dialkylmetall)quadratate der elemente aluminium,gallium und indium

The reaction of squaric acid, H₂C₄O₄, with the trialkyl derivatives of aluminium, gallium and indium (R₃M with R = CH₃, C₂H₅) in a $\text{1}\text{2}$ molar ratio leads to bis(dialkylmetal) squarates. The Ga and In compounds dissociate in water forming R₂M⁺ and C₄O₄^2? ions. From these solutions the squarates crystallize as mono- and dihydrates, respectively. The vibrational spectra (IR and Raman) are discussed.     

The chemical oxidation and electronic spectra of the complexes trans-[M(CNR)2(Ph2PCH2CH2PPh2)2] (M = Mo or W)

Oxidation of the complexes $\text{trans}$-[M(CNR)₂(dppe)₂] (A) (M = Mo or W; R = Me, Bu^t or CH₃C₆H₄-$\text{4}$; dppe = Ph₂PCH₂CH₂PPh₂) with diiodine or silver (I) salts gives the paramagnetic cations $\text{trans}$-[M(CNR)₂(dppe)₂]⁺, (M = Mo, R = CH₃C₆H₄-$\text{4}$; M = W, R = Bu^t) and $\text{trans}$-[M(CNR)₂(dppe)₂]²⁺ (M = Mo, R = Me or CH₃C₆H₄-$\text{4}$; M = W, R = Me or Bu^t). Mixtures of products are generally produced when dichlorine or dibromine are the oxidising agents, however pure salts, the seven-coordinate complex cations [MX(CNC₆H₄CH₃-$\text{4}$)₂(dppe)₂]⁺ (B, X = Cl or Br) have been isolated. A simple molecular orbital scheme is proposed for complexes (A) and used to discuss their electronic spectra and their oxidation.     

Mechanistic Aspects of Inorganic Reactions. ACS Symposium Series 198 : (Ed. D.B. Rorabacher and J.F. Endicott), American Chemical Society,Washington DC, 1982, x + 486 pages, $ 58.95 ($ 48.95, U.S.A. and Canada). ISBN 0-5412-0734-8.

Norbornadiene (NBD) is more easily displaced from PtMe₂ (NBD) by other ligands than is cyclooctadiene (COD) from PtMe₂ (COD). cis-PtMe₂L₂ (L = py, $\text{1}\text{2}$tmen, $\text{1}\text{2}$en, NH₃, DMSO) have been prepared in this way. cis-PtMe₂py₂ is very reactive toward oxidative addition. Pyridine can usually be removed from the platinum(IV) products using acid. NBD is even more readily displaced from Pt(CF₃)₂ (NBD), giving cis-Pt(CF₃)₂L₂ (L = py, $\text{1}\text{2}$tmen, $\text{1}\text{2}$en, NH₃, DMSO, NCR, DMF, CN^?, I^?, acac^?). cis-Pt(CF₃)₂py₂ with CF₂I gives fac-Pt(CF₃)₃py₂I.     

Reaktionen von metall-koordiniertem kohlenmonoxid mit yliden: XVII. Darstellung eines molybdän- und wolframkomplexes mit η3-gebundenem trimethylsiloxybutenon-liganden durch silylierung der phosphonium-metall-enolat-vorstufe

The reaction of the phosphonium metallates Me₄P[C₅R₅(CO)(Me₃P)$\text{MC(O)=CHC(O}$)R′] (M = W, R = H, R′ = Et (1a); M = Mo, R = Me, R′ = Me (1b)) with the silylating reagent Me₃SiOSO₂CF₃ yields the neutral complexes C₅R₅(CO)(Me₃P)$\text{MC(OSiMe}{}_3\text{)=CHC(O}$)R (2a, 2b) bearing a chelating O(2), C(4)-trimethylsiloxybutenone ligand. The structure of the new compounds is established by the IR, ¹H and ³¹P NMR spectra.     

Yield of I(2Psol:12) in the photodissociation of CH2I2

The production of I(²P_{$\text{1}\text{2}$}) in the photolysis of CH₂I₂ has been studied optoacoustically at excitation wavelengths between 365.5 and 247.5 nm. Bands found at 32200 and 47000 cm^?1 correlate with I(²P_{$\text{3}\text{2}$}) whilst those at 34700 and 40100 cm^?1, which correlate with I(²P_{$\text{1}\text{2}$}), give final ²P_{$\text{3}\text{2}$}/²P_{$\text{1}\text{2}$} ratios of 1.75 and 1.1, respectively, after curve crossing.     

Trimethymetall-urotropinaddukte des aluminiums,galliums, indiums und thalliums

Reactions of urotropine (C₆H₁₂N₄) with trimethylmetal derivatives of Al, Ga, In und Tl in various ($\text{1}\text{1}$$\text{1}\text{4}$) molar ratios lead to stable and monomeric $\text{1}\text{1}$, $\text{1}\text{2}$ or $\text{1}\text{3}$ adducts in good yields, but no $\text{1}\text{4}$ addition product could be isolated. The vibrational spectra (IR and Raman) of all compounds are recorded and partly assigned. Some characteristic frequencies of the C₆N₄-skeletons clearly show the symmetry changes in the series of the $\text{1}\text{1}$ → $\text{1}\text{2}$ → $\text{1}\text{3}$ adducts (C_3ν → C_2ν → C_3ν). The X-ray structure determinations of C₆H₁₂N₄·.GaMe₃ (MeCH₃) and C₆H₁₂N₄·.2GaMe₃, are in good agreement with the vibrational spectra. Both compounds crystallize in monoclinic space groups (P2₁ and C2/c). The GaN distances are around 214 pm, and the values for the C₆N₄-skeletons are not significantly different from those for free urotropine.     

Synthesis,Reactions and Catalytic Activities of a Cationic Acrylonitrile-Rhodium(I) Complex

Reaction of RhCl (CO)(Ph₃P)₂(Ph₃P = triphenylphosphine) with AgClO₄ in acrylonitrile at 30°C produces a new cationic rhodium(I) complex, [Rh(CH₂CHCN)(CO) (Ph₃P)₂]ClO₄ ($\text{1}$) and AgCl. The ¹H-NMR and IR spectra of $\text{1}$ suggest that acrylonitrile is coordinated to rhodium through the π-system of the vinyl group. The complex $\text{1}$ reacts with molecular hydrogen to give a propionitrile-rhodium(I) complex, [Rh(CH₃ CH₂CN) (CO)(Ph₃P)₂ClO₄($\text{2}$) where the coordination of propionitrile through nitrogen is suggested by the ¹H-NMR and IR spectral data. The coordinated acrylonitrile in $\text{1}$ is readily replaced with triphenylphosphine and propionitrile to give [Rh(CO)(Ph₃P)₃] ClO₄ and $\text{2}$, respectively. The complex $\text{1}$ is catalytically active for the hydrogenation and polymerization of acrylonitrile at 25°C under the atmospheric pressure of hydrogen.     

The effect of the solvent upon the rates and machanisms of organometallic reactions: VII. A 19F NMR study of complexation of CF3 HgX (X = Cl,I, OCOCF3)

The concentration and temperature dependence of J(¹⁹⁹HgC¹⁹F) for solutions of CF₃HgX (X = Cl, I, OCOCF₃) in various solvents shows that in inert solvents these molecules exist mainly as non-solvent dimers (X = I or OCOCF₃) or as monomers (X = Cl). In strongly coordinated solvents $\text{1}\text{2}$ complexes are largely formed from CF₃HgX and the electron-donating solvent molecules. In pyridine solution an equilibrium exists between the $\text{1}\text{1}$ and $\text{1}\text{2}$ complexes. Complexes of the type CF₃HgX·D are T-shaped and have a higher relative content of s-electrons in the HgCF group compared with tetrahedral CF₃HgX·2D complexes.     

Coordination chemistry of higher oxidation states. 10 [1]. Oxofluoroanions of osmium(VIII) [OsO4F2]2− and [OsO3F3]−

Trioxotrifluoroosmates(VIII) M[OsO₃F₃] (M = Cs, Rb, K) have been prepared by direct combination of OsO₃F₂ and the appropriate alkali fluoride MF. The reaction of OsO₄ with M′F (M′ = Cs, Rb) in aqueous solution produces the tetraoxodifluoroosmates(VIII) M′₂[OsO₄F₂]. On the basis of their vibrational spectra the assignment of a $\text{fac}$ (C_3v) structure to [OsO₃F₃]^? and a $\text{cis}$ (C_2v) to [OsO₄F₂]^2? is proposed. The electronic spectra of the anions have been recorded and are interpreted using the optical electronegativity concept.     

Refinement of β-LiIO3 crystal structure by use of zeeman effect on the NQR line and ir-reflection spectra

The NQR Zeeman effect of ¹²⁷I quadrupole resonance (±$\text{1}\text{2}$ ↓ ±$\text{3}\text{2}$ transition) and the polarized IR spectra of a single crystal of β-LiIO₃ have been studied. The z-axes of the EFG orientation in the unit cell were determined; the EFG asymmetry parameter for the ¹²⁷I nuclei was refined giving η = 0.027 ± 0.003 at 300 K for β-LiIO₃. The dichroic ratio in the (100) crystal plane over the I-O stretching vibration region has been measured from polarized spectra and calculated on the basis of an “oriented gas” model by the use of refined structural data. Comparison of some spectral, structural and quantum-chemical characteristics of both β- and α-modifications of LiIO₃ crystal has been made.     

The rotational spectrum and molecular properties of a hydrogen-bonded dimer of phosphine and hydrogen fluoride

⁵⁷Fe Mössbauer spectra have been obtained for Fe(p-CH₃C₆H₄SO₃)₂ between 2.3 and 300 K in zero field, and at 2.3 and 4.2 K in longitudinal applied magnetic fields ranging from 1.1 to 5.6 T. The complex is a fast-relaxing paramagnet under all conditions studied and there is no evidence of antiferromagnetic exchange coupling. The FeO₆ chromophore is distorted by a trigonal elongation and the orbital ground state is the [($\text{2}\text{3}$)^{$\text{1}\text{2}$}|±2〉 ? ($\text{1}\text{3}$)^{$\text{1}\text{2}$}|?1〉] doublet. The temperature dependence of the quadrupole splitting has been analysed via a crystal-field model to provide estimates of the axial field splitting parameter Ds = -93 cm^-1, spin-orbit coupling constant λ = -70 cm^-1, and fine structure constant Dσ = -28 cm^-1. The magnetic properties of the complex are described by treating the ground state as a non-Kramers doublet with fictitious spin ? = $\text{1}\text{2}$. Five separate Mössbauer-Zeeman spectra can be fitted in this spin-hamiltonian approximation with identical values of the g- and A-tensor components, viz. g_⊥ = 1.0, g_u = 9.0; A_⊥ ≈ 2.0 mm s^-1. A_u = -1.79 mm s^-1. The trigonal z axis, the z axis of the electric field gradient tensor, and the easy axis of magnetisation are collinear, and the saturation value of the internal hyperfine field along this axis is +13.0 T.     

Molecular beam chemiluminescence XI: kinetic and internal energy dependence of the NO + O3 → NO2*,→ NO23 reaction

Seeded supersonic NO beams were used to study the kinetic energy dependence of both the electronic (NO₂^*) and vibrational (NO₂³) chemiluminescence of the NO + O₃ reaction. In addition the electronic CL is found to be enhanced by raising the NO internal temperature. This is shown to be due to enhanced reactivity of the NO(²Π,_{$\text{3}\text{2}$}) fine structure component. By difference NO(²Π_{$\text{1}\text{2}$}) is concluded to yield predominantly groundstate NO₂³. The excitation function for NO₂^* formation from NO(²Π_{$\text{3}\text{2}$}) is of the form σ_{$\text{3}\text{2}$}(E) = C(E/E₀ - 1)ⁿ over the 3–6 kcal energy range where n = 2.4 ± 0.15, C = 0.163 Ų and E₀ = 3.2 ± 0.3 kcal/mole. Vibrational IR emission from NO₂³ has an energy dependence different from electronic NO₂^* emission, confirming that emitters are formed predominantly in distinct reaction channels rather than via a common precursor (either NO₂^* or NO₂³). The short wavelength cutoff of the CL spectra recorded at elevated collision energies E ? 15 kcal/mole corresponds to the total available energy. These and literature results are discussed in the light of general properties of the (generally unknown) ONO₃ potential energy surfaces. The formation of electronically excited NO₂^* rather than energetically preferred O₂ (¹ Δg) (Gauthier and Snelling) can be rationalized in terms of surface hopping near a known intersection of potential energy surfaces more easily than by vibronic interaction in the asymptotic NO₂ product.     

High-resolution HeI and HeII photoelectron spectra of the Zn 3d and Cd 4d orbitals in the zinc and cadmium dihalides: Ligand field splittings and intensity variations

We have recorded the high-resolution HeI and HeII photoelectron spectra of the Zn 3d and Cd 4d levels in gas-phase MX₂ molecules (M = Zn, Cd; X = Cl, Br, I). The d level spectra split into five peaks due to the combined effect of spin-orbit splitting and ligand field splitting on the d⁹ hole state, and the spectra have been fitted to a crystal field hamiltonian involving the cubic (C₄⁰) and non-cubic (C₂⁰) parts of the field from the halide ligands. Additional peaks in some spectra are due to vibrational splitting and configuration interaction. The ¦C₂⁰¦ value increases substantially from the chloride to the iodide for both Zn and Cd. Calculations of both the crystal field (C_{2 CF}⁰) and valence (C_{2 val}⁰) parts of C₂⁰ show that the increase in observed C₂⁰ is due to the C_{2 val}⁰ term attributed to the increase in covalency from the chlorides to the iodides. Shifts in the peak position due to the 2Σ_{$\text{1}\text{2 g}$} and 1Π_{$\text{3}\text{2 g}$} states from those expected on the ligand field basis. are attributed to slight bonding effects. These effecs cause a large discrepancy between calculated and observed C₄⁰ values. The intensities of the five Zn 3d peaks change markedly from HeI- to HeII-excited spectra. The Xα SW method has been used to calculate the intensities of the σ, π and δ 3d orbitals as a function of photon energy. These calculations show dramatic changes in intensity due. for example. to shape resonances. There is usually qualitative agreement between calculated and observed intensities.     

Unusual rearrangement of σ-vinylpalladium complexes into η2-olefin complexes. The structure of (η2-1-triphenylphosphonium-2-carbomethoxyethylene)(triphenylphosphine)iodopalladate

β-Substituted σ-vinylpalladium complexes [Pd(σ-CHCHCOOR)(PPh₃)₂(X)] (I) (X = Cl, I; R = Me, Et) have been obtained by interaction of the E- and Z-β-halogen acrylates with tetrakis(triphenylphosphine)palladium. On heating complexes I rearrange into isomeric η²-olefin-ylidepalladium complexes [$\text{P}$$\text{dCH(COOR)-C}$HPPh₃(PPh₃)(X)] (II). The structure of these com X-ray study of the compound with X = I, R = Me.     

Branching ratio for the production of I2Psol12) in the photodissociation of I2

The production of atomic iodine in the ground (²Pfrsol|3/2) and electronically excited (²P$\text{1}\text{3}$) states following laser-induced photodissociation of I₂ the region 425–498 nm was monitored directly by resonance spectroscopy. The branching ratio for iodine atom formation. R = [I(²P$\text{1}\text{2}$)]/[I(²P$\text{3}\text{2}$)], is above 0.5 in the region 495–498 nm in agreement with the recent observation of laser action on the atomic transition at 1315 nm following photolysis of I₂ using a dye laser. The present experiments permitted deconvolution of the I₂ continuous absorption spectrum below 498 into contributions from the B³ Π_o,u → X ¹Σ_g⁺ and ¹Π_tu → X¹σ_g^? transitions.     

Interactions magnétiques dans des groupements binucléaires [Fe2O7]8− au sein de Na8Fe2O7

The magnetic interaction in the structural units [Fe₂O₇]^8?, built of two corner-sharing FeO₄ tetrahedra, in Na₈Fe₂O₇ ($\text{Na}{}_2\text{O}\text{Fe}{}_2\text{O}{}_3\text{=}\text{4}\text{1}$) has been studied by magnetic susceptibility measurements (4.2–500 K). An exchange integral $\text{J}\text{K}{}_{\mathrm{<mtext>B</mtext>}}$ of ?37 K is obtained by comparison of the experimental values and the calculated ones using a Heisenberg-Dirac-Van Vleck-type Hamiltonian ? = $\text{?2J}\text{S}\text{?}{}_1\text{S}\text{?}{}_2$. The hypothesis of magnetically isolated [Fe₂O₇]^8? groups is corroborated by Mössbauer spectroscopy between 1.5 and 77 K. The susceptibility measurements of the solid solutions Na₈Fe_2?xM_xO₇ (M = Al, Ga; 0 ≤ x ≤ 0.2 for Al; 0 ≤ x ≤ 2 for Ga) leads to the same conclusion of the existence of isolated Fe³⁺Fe³⁺ pairs in Na₈Fe₂O₇. The type of substitution of Fe by Al or Ga is determined; homonuclear Fe³⁺Fe³⁺ and M³⁺M³⁺ pairs and heteronuclear Fe³⁺M³⁺ pairs are formed.     

Energy levels of iodine monochloride near the first dissociation limit

Absorption transitions to vibrational levels close to the A state dissociation limit of ICI have been examined using a two-photon sequential absorption technique. The discrete rotational structures of I³⁷ Cl bands to within 0.7 cm^?1 of the limit have been selectively excited and analysed. A value of 17557.514 ± 0.030 cm^?1 has been obtained for the I(²P^o_{$\text{3}\text{2}$}) + Cl(²P^o_{$\text{3}\text{2}$}) dissociation energy D_e, relative to the minimum of the ICI ground state potential well. The two-photon technique can be used to excite and display separately the high resolution absorption spectra of different isotopic species of a molecule which are contained in a mixture.