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.     

Structural effects on valence tautomerism : VII. An NMR and molecular mechanics study of the steric effects of t-butyl substituents on the cycloheptatriene-norcaradiene equilibrium of 7-cyano-7-m

7-Cyano-7-methylcycloheptatrienes containing one t-butyl group on the 1-position ($\text{2}$) or two t-butyl groups on the 1- and 3-, 1- and 4-, or 1- and 5-positions ($\text{3}$, $\text{4}$, or $\text{5}$, respectively) were synthesized and their cyclo- heptatriene (CHT)-norcaradiene (NCD) equilibria measured by variable-temperature ¹H NMR for CS₂-CD₂Cl₂ solutions. The ¹H NMR chemical shifts of the 7-methyl group indicate that these compounds are composed of essentially one CHT and one NCD tautomer with an endo geometry of the methyl group. The introduction of a t-butyl group at the 1-position of 7-cyano-7-methylcycloheptatriene ($\text{1}$) markedly shifts the equilibrium to the NCD side and the addition of the second t-butyl group further favors the NCD form, with the NCD populations for $\text{2}$, $\text{3}$, $\text{4}$, and $\text{5}$ at 25 °C 70.9, 96.5, 92.3, and 99.3%, respectively. An application of molecular mechanics (MMPI) calculations to various t-butylated CHT-NCD systems suggests that the t-butyl groups sterically destabilize the CHT form more than the NCD form, bringing about increased NCD populations.     

Comparison of reactivity of Ar(3Po) and Ar(3P2) metastable states. Products of quenching by some halogen-containing compounds

Vacuum UV emission from the products of quenching ofAr(³P_o) and Ar(³P₂) by several reagents has been compared. The large differences suggest that Ar(³P_o) and Ar(³P₂) preferentially yield respectively the D($\text{1}\text{2}$) and B($\text{1}\text{2}$) excited states of ArBr^★ or ArCl^★, which show specific, but very different, predissociation patterns.     

The thiolate anion as a nucleophile Part XI. Effect of the size of the nucleophile

The nucleophilic substitution reactions of some simple fluorobenzenes, C₆H_6?xF_x with sodium methanethiolates Na⁺SR^?(R=Et, $\text{i}$-Pr, $\text{t}$-Bu) have been studied. Some fully substituted products, C₆H_6?x(SR)_x, could be obtained in DMF as solvent with R = Et and $\text{i}$-Pr, but not when R = $\text{t}$-Bu. All the new products isolated have been characterized by elemental analysis, and NMR (H-1 and F-19), infrared and mass spectroscopy.     

Action of tert-butyl azidoformate on the conjugate bases of 1,2,3,4-tetrahydro-9H-carbazole and other indole derivatives

tert-Butyl azidoformate ($\text{2}$) reacts with the conjugate bases of $\text{3a}$, $\text{7a}$, $\text{9}$ (R¹ = R² = CH₃), and $\text{9}$ (R¹ = CH₃, R² = H) to give products [$\text{4}$, $\text{8}$, $\text{12}$, and $\text{14}$, respectively] in addition to the expected N-(tert-butoxycarbonyl)indole derivatives.     

Reaktionen an komplexgebundenen Liganden. XXXII.: Synthese und eigenschaften von heteronuklearen mangan-chrom-komplexen mit distickstoff- diazen- und hydrazin-brükenliganden

Synthesis and properties of C₅H₅(CO)₂Mn-N₂H₄-Cr(CC)₅$\text{(1)}$, C₅H₅(CO)₂Mn-N₂H₂-Cr(CO)₅$\text{(2)}$ and C₅H₅(CO)₂Mn-N₂-Cr(CO)₅$\text{(3)}$ are reported. $\text{(1)}$, $\text{(2)}$ and $\text{(3)}$ constitute the first series of heteronuclear complexes in which N₂, N₂H₂ and N₂H₄ are bound to identical metal centers. $\text{(1)}$ and $\text{(3)}$ are obtained by reacting C₅H₅Mn(CO)₂N₂H₄ respectively with Cr(CO)₅THF, $\text{(2)}$ by oxidation of $\text{(1)}$. $\text{(2)}$ disproportionates by addition of base yielding $\text{(3)}$ and H₂. The IR Spectrum of $\text{(2)}$ allows the assignment of five normal vibrations of the diazene ligand; in the IR spectrum of the deuterated analogue all six normal vibrations can be assigned. The ¹H-NMR spectrum of $\text{(2)}$ yields the coupling constant of protons on NN double bonds for the first time; the value of ³J_HH  23,5 Hz points to a trans structure of $\text{(2)}$.     

Perhalogenmethylmercapto-heterocyclen,IX (perchlormethylmercapto)- und (perfluormethylmercapto)pyridine

Methods of substituting pyridine by perhalogenomethylmercapto groups are discussed. The side chain chlorination of 2-(methylmercapto)pyridine leads gradually to 2-(trichloromethylmercapto)pyridine hydrochloride ($\text{1a}$) and 2-(trichloromethylmercapto)pyridine ($\text{1b}$). Neither a direct reaction of pyridine with CF₃SCl nor the way over a Grignard reaction or a sulfenylcarboxylate lead to CF₃S-substituted products. Reactions of pyridine and bromopyridines with Hg(SCF₃)₂ yield 1:1-adducts ($\text{2a-d}$) only. Lithium tetrakis(1,2-dihydro-1-pyridyl)aluminate (LDPA) reacts with CF₃SCl to give 3-(trifluoromethylmercapto)pyridine ($\text{3}$); in addition a disubstituted product can be identified massspectroscopically. ¹H- and ¹⁹F-NMR-spectra are reported.     

Nucleophilic reactions of fluoroolefins.IV. Regioselectivity in the reactions of 1-phenylpentafluoropropenes with alkyllithium reagents

Reactions of 1-phenylpentafluoropropenes $\text{1a}$–$\text{c}$ with a number of alkyllithium reagents were investigated in detail. In all cases mixtures of 1-alkly-1-phenyltetrafluoropropenes $\text{2}$ and 2-alkyl-1-phenyltetrafluoropropenes $\text{3}$ were obtained. The ratio of products $\text{2}$ and $\text{3}$ is strongly influenced by both the electronegativity of the benzene ring substituents and the bulk of the alkyl group of the alkyllithium reagents. The increase of both of these factors favours formation of 2-alkyl-substituted alkenes $\text{3}$ with a reduced yield of 1-alkyl-substituted alkenes $\text{2}$. The influence of the benzene ring substituents in alkenes $\text{1}$ obeys the Hammett type correlation, while the influence of the bulk of the alkyllithium reagents exhibits good relationships with the Fellous and Luft scale of steric substituent constants E^x_s ; no linear correlation with other scales of steric constants was found. Overall regioselectivity, in the reaction of 1-phenylpentafluoropropenes $\text{1}$ with alkyllithium reagents, considering both the influence of the benzene ring substituents and steric factors, is expressed by the Pavelich-Taft type equation. Observed direction of the influence of the bulk of the alkyllithium reagents on the ratio of products $\text{2}$ and $\text{3}$ is interpreted in terms of steric strains influencing the geometry and free energy of the supposed intermediates involved in these reactions.     

New defect vanadium dioxide phases

Two new monoclinic V₂O₄ phases were prepared at high pressure from the regular monoclinic (M₁) form of V₂O₄. The unit cell dimensions for the unmodified monoclinic (M₂) phase are: a = 9.083, b = 5.763, c = 4.532 Å, and β = 91.30°. The space group $\text{C 2}\text{m}$ is consistent with the crystallographic data. The new vanadium dioxide exhibited a structural transition and an abrupt, reversible change in resistivity (approx. 4 orders of magnitude) at 66°C similar to that observed in M₁-type V₂O₄. This new form of V₂O₄ is believed to be stabilized by chemical and structural defects. Controlled substitution of V⁵⁺ for V⁴⁺ in the structure led to yet another monoclinic (M₃) phase. This phase is closely related to the M₂ phase. The M₃ unit cell dimensions are: a = 4.506, b = 2.899, c = 4.617 Å, and β = 91.79°, having the space group $\text{P 2}\text{m}$. The substitution of V³⁺ yielded only monoclinic (M₁) derivatives. The modified products have varied semiconductor to metal transition temperatures which depend on the type and amount of substitution and defect structure.     

Über reaktionen mit aluminiumalkylen: XVII. Spektroskopische untersuchungen von komplexen aus butanoliden und äthylaluminium-verbindungen

Three different types of butanolide complexes with Et_nAlCl_3?n in the molar ratios $\text{1}\text{1}$ and $\text{1}\text{2}$ have been investigated by IR with ^1M NMR spectroscopy. The butanolides form $\text{1}\text{1}$ and $\text{1}\text{2}$ complexes with ethylaluminium halides, but with triethylaluminium only $\text{1}\text{1}$ complexes are formed. The complexes are intermediates in the cleavage of butanolides.     

Microwave-optical double resonance in molecular ions. Co+

Microwave—optical double resonance signals have been detected in a mass-selected ion-beam spectrometer for ¹²C¹⁶O⁺. With the optical excitation of fluorescence from the R₁ ($\text{1}\text{2}$) line of the (0,0) band of the A²Π_{$\text{3}\text{2}$} ← X²∑ transition of 20350.6 cm^?1, the microwave resonances occurred at 118101.8 ± 0.2 MHz and at 117694 ± 2 MHz corresponding to the N= 1, J = $\text{3}\text{2}$ ← N = 0, J = $\text{1}\text{2}$ and the N = 1, J = $\text{1}\text{2}$ ← N = 0, J = $\text{1}\text{2}$ transitions.     

Reactions of triphenylarsine oxide with aqueous hydrogen fluoride: Crystal structure of bis(triphenylarsine oxide)hydrogen(I) tetrafluoroborate

Fluorination of triphenylarsine oxide by aqueous hydrogen fluoride (1–40%) in the absence of glass readily gives triphenylarsine difluoride. When the reaction with dilute (1%) aqueous hydrogen fluoride is carried out in borosilicate glass apparatus, the glass participates in the reaction resulting in the formation of the crystalline 2:1 adduct 2Ph₃AsO·HBF₄. Crystals of this compound are monoclinic, $\text{P}$2₁/$\text{c}$, $\text{a}$ = 12.926(4), $\text{b}$ = 17.819(6), $\text{c}$ = 14.994(4) Å, β = 98.97(3)°, Z = 4. The structure contains cations [(Ph₃AsO)₂H]⁺ in which $\text{O}\text{?}$O is 2.44(2)Å, and anions BF₄^?.     

Addition products of hydrazine derivatives to azo-alkenes - III. α-phenylhydrazino-phenylhydrazones

The addition of phenylhydrazine to phenylazo-alkenes $\text{4}$ yields α-(1-phenylhydrazino)-phenylhydrazones $\text{1}$. The reaction of phenylhydrazine with α-halogenated carbonyl compounds $\text{5}$ affords either $\text{1}$ or the isomeric α-(2-phenylhydrazino)-phenylhydrazones $\text{2}$. Structures $\text{1}$ and $\text{2}$ (>N-NH₂ and-NH-NH- groups, respectively) can be differentiated by ¹H NMR in DMSO-D₆ solution. Possible pathways of the reactions leading to either $\text{1}$ or$\text{2}$ are discussed. Compounds $\text{1}$ are found to be precursors of phenylosazones $\text{6}$.     

ESR studies on the reactions of sulphite radical anion,SO3.̄−, with nitroalkane compounds in aqueous solutions

The reactions of the sulphite radical anion, SO₃^{$\text{.}\text{?}$?} (generated from the Ti³⁺-H₂O₂-Na₂SO₃ system at pH 9), in aqueous solutions with some nitroalkane compounds were investigated by using a rapid-mixing flow technique coupled with electron spin resonance (ESR) which can detect the radicals having a lifetime of 5–100 ms. The SO₃^{$\text{.}\text{?}$?} radical added to the double bond of CN in the nitroalkane aci-anions which are the main form of nitroalkanes in aqueous alkaline solutions. From the observed hyperfine splitting constants of the SO₃^{$\text{.}\text{?}$?} adducts of nitroalkane aci-anions, the preferred conformation of the adducts was deduced.     

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.     

The study of redox reactions of bisarenechromium complexes by the rotating disk and the rotating ring disk electrode techniques: III. Cathodic reduction of chromium(0) π-complexes and the corresponding arenes in dimethyl sulfoxide solutions

The rotating disk (RDE) and the rotating ring-disk (RRDE) electrode techniques have been employed to study the cathodic behavior of eight bisarenechromium complexes and seven corresponding arenes in DMSO solutions. In the first electrochemical step of the process reversible addition of one electron results in anion-radicals, whose formation has been demonstrated for certain arenes and chromium π-complexes by oxidation of these particles on the ring electrode.Substituents on different ligands of bisarenechromium complexes were found to exert pronounced mutual influences. The role of the chromium atom in transfer of electronic effects from one ligand to another is discussed.It was found that a linear correlation exists between the variations in the free energy of the equilibrium “initial compound

anion-radical” (due to coordination of free arene with chromium which is displayed as a shift of the cathodic process half-wave potential ΔE_{$\text{1}\text{2}$}^CL) and the half-wave potential of the oxidation of the corresponding Cr⁰ π-complex to a cation E_{$\text{1}\text{2}$}^X ΔE_{$\text{1}\text{2}$}^CL = a + αE_{$\text{1}\text{2}$}^X At E_{$\text{1}\text{2}$}^X < ?0.3 V, complex formation slows down the cathodic process and at E_{$\text{1}\text{2}$}^X > ?0.3 V the process is facilitated.     

Perhalogenmethylmercapto-heterocyclen, (VII) [1] konkurrenzreaktionen elektronenarmer,substituierter aromaten um die halogenmethylmercapto- BZW. Chlorgruppe von Cl3-nFnCSCl in starken saeuren

Electron-deficient aromatics, such as 2,5-bis(trifluoromethylmercapto)thiophene ($\text{1a}$) or (trifluoromethylmercapto)benzene ($\text{8a}$), react with F₃CSCl in the presence of F₃CSO₃ as a catalyst to give mainly 3-chloro-2,5-bis(trifluoromethylmercapto)thiophen ($\text{3a}$) and 1-chloro-4- or 2-(trifluoromethylmercapto)benzene ($\text{10}$, respectively. This reaction competes with the one expected to result in 2,3,5-tris(trifluoromethylmercapto)thiophene ($\text{2a}$) and 1,4- and 1,2-bis(trifluoromethylmercapto)benzene ($\text{9}$,$\text{9′}$), respectively. Further reactions of deactivated aromatics with Cl_3-nF_nCSCl show that the chlorine substitution is in general catalysed by strong acids. Reaction mechanisms are proposed for both Substitutions. The Cl_3-nF_nCS group in aromatics exerts a -M-effect in the case of an attack of a positive ion, e.g. H^⊕, the well-known +M-effect in the case of reactions with positively polarized molecules, e.g. CF₃S^β+Cl^β-.     

The octant rule. XIV. synthesis and circular dichroism of α-exo and endo-deuteriobicyclo[3.2.1]octan-3-one and 6,6-dimethybicyclo[3.1.1]heptan-3-one

(1R,5S)-2S-Deuteriobicyclo[3.2.1]octan-3-one ($\text{1}$) and (1R,5S)-2R-Deuteriobicyclo[3.2.1]octan-3-one ($\text{2}$), prepared by diazomethane ring enlargement of (1S,4R)-2(exo)-deuteriobicyclo-[2.2.1] heptan-2-one and (1S,4R)-2(endo)-deuteriobicyclo[2.2.1]heptan-2-one respectively, both gave (?) n-π^* circular dichroism (CD) Cotton effects, Δε^max₂₉₄ = ?0.05 and Δε^max₂₉₄=?0.1, respectively, in hydrocarbon solvent. (1S,5R)-2S-Deuterio-6,6-diaethylbicyclo[3.1.1] heptan-3-one ($\text{3}$) and (1S,5R)-2R-deuterio-6,6-dimethylbicyclo[3.1.1] heptan-3-one ($\text{4}$), prepared from (-) myrtenal, both exhibited extraordinary vibrational fine structure for the n-π^* CD transitions observed in hydrocarbon solvent and oppositely?signed CEs, Δε^max₂₈₂=?0.01 and Δε^max₂₇₉=+0.01 respectively in CF₃CH₂OH solvent.     

Molecular predissociation dynamics revealed through multiphoton ionisation spectroscopy. III. New 1A2 and 1B1 rydberg states in H2S D2S

Two new Rydberg series in H₂S and D₂S habe been characterized as three-photon resonances in four-photon ionisation spectrometry. Members of the two series exhibit sufficient rotational structure to permit characterisation of their electronic symmetries as, respectively. A₂ and B₁. The first Rydberg series is identified with the (one-photon forbidden) excitations npb₂ ← 2b₁ (¹A₂ ← $\text{X}$¹A₁) on the basis of the observed quantum defects. Geometry considerations indicate that second series, of ¹B₁ states, also arises as a result of electronic promotion from the highest occupied 2b₁ orbital. The acceptor (a₁) Rydberg orbitals possess substanial s character, but the polarisation dependence of the various ¹B₁-$\text{X}$¹A₁ three-photon transition probabilities their hybrid I character, d (and quite possibly p) functions contribute also. The results provide further clear demonstration of the way in which multiphoton excitations, and MPI techniques in particular, can complement conventional one-photon absorption techniques. Members of both series are predissociated. Vibronic predissociation rates are found generally to decline with increasing n and to be slower in D₂S than in H₂S. The lowest (n = 4) member of the ¹A₂ series in both isotopic species appears immune from rovibronic predissociation but higher members show evidence of a ($\text{J}$_a²)-dependent rotationally-induced predissociation, the severity of which increases dramatically with n. This observation is explained in terms of electronic-rotational Coriolis coupling to a dissociated ¹B₂ state is presumed to be responsible for the observed ($\text{J}$_b²)-dependent heterogeneous predissociation of the ¹B₁ (n = 6) member in H₂S. However, the dominant rotationally-induced predissociation mechanism that affects the counterpart in D₂S scales with ($\text{J}$_a²). Wherever possible comparisons are drawn with the known spectroscopy and photophysics of the isovalent molecules H₂O and D₂O.     

X-ray molecular structure of the 1:1 adduct of [FeH(CO)4]− and dimethyl acetylenedicarboxylate. η3-[trans-2,3-bis(methoxycarbonyl)acryloyl]tricarbonylferrate

The crystal structure of a bis(triphenylphosphine)iminium salt of the 1:1 adduct of [FeH(CO)₄]^? and dimethyl acetylenecarboxylate has been determined from three-dimensional X-ray data collected by the counter method. Single crystals belong to the triclinic space space group P$\text{1}$, with two units of [C₃₆H₃₀NP₂]⁺[C₁₀H₇FeO₈]^? in a cell of dimensions: $\text{a}$ = 13.918(2), $\text{b}$ = 15.669(5), $\text{c}$ = 9.909(2) Å, $\text{α}$ = 91.22(3), $\text{β}$ = 94.83(2), and $\text{γ}$ = 77.62(2)°. The structure was refined to a conventional $\text{R}$ of 0.068 for 5373 observed

reflections. The resulting structure indicates that the complex anion is η³-[$\text{trans}$-2,3-bis(methoxycarbonyl)acryloyl]tricarbonylferrate, the coordination around the iron atom being described as a considerably distorted trigonal bipyramid. A comparison of the present structure with the structures of related complexes suggests that the η³-acryloyl portion is best represented as an intermediate of (η³-allyl) with the oxygen atom and (η²-olefin + η¹-acyl). The short Fe-C(acyl) length of 1.897(5) Å implies an enhanced back-donation of electrons from the iron atom to the acyl group.