The preparation of fluxional tetrahydrides, (R  H or Me) and their reactions with CO,ButNC or HBr

The cyclometallated monohydrides

(R  H or Me) react with NaOPrⁱ/PrⁱOH/H₂ to give fluxional tetrahydrides, probably

. These are highly fluxional having magnetically equivalent hydridic hydrogens, even at ---100°C. When treated with HBr,

, gives

and with CO it gives a mixture of complexes which are probably

(2 isomers) and

. When treated with Bu^tNC this tetrahydride undergoes similar reactions but another (major) product is formed which appears to be binuclear and fluxional and is probably of type

, with four bridging hydrogens.     

A direct synthesis of 1,3-bis(bromomagnesio)propane

Careful addition of 1,3-dibromopropane

to magnesium in Et₂O yields 1,3-bis(bromomagnesio)propane

which is purified via “magnesacyclobutane”

. Reactions of

with H₂O, CO₂, HgBr₂ and Me₃SnCl are reported. MgBr₂ catalyses the decomposition of

to allylmagnesium bromide

.     

Diversity of the gramicidin a spatial structure: two-dimensional 1H nmr study in solution

Theoretical consideration reveals a unique relationship between NMR spectral parameters and possible types of the gramididin A spatial structure. By means of two dimensional NMR spectroscopy four distinct species were detected simultaneously in ethanol solution. Comparison of experimental data and theoretical conclusions demonstrates that species 1 and 2 are left-handed parallel double helices

differing in relative arrangement of the two polypeptide chains within the dimers, species 3 is left-handed antiparallel double helix

, and species 4 is a mirror image of species 1, i.e. right-handed parallel double helix

. The results are compared with those on spatial structures of the peptide in complex with cesium (right-handed antiparallel double helix

) and of the gramicidin A transmembrane ionchannel (N-terminal to N-terminal single-stranded dimer

).     

Excited-neutral-metastable SO2 formation in the , O3-olefin-SO2, and active nitrogen-SO2 systems

Long-liied (τ > 10^?3 s), electronically-excited (E * > 4 eV) neutral metastables, whose formation was attributed to the presence of SO₂, were observed in the three titled systems. Their possible identity as collisionally-accessed metastable states of the normal

, cyclic

, or superoxide

isomers of SO₂ is discussed.     

The composition of the evolved gases from the thermal decomposition of certain metal sulfates

By the use of TG—MS, the thermal dissociation of anhydrous CuSO₄ and Al₂(S0₄)₃ was found to proceed according to the reactions:

followed by the reactions:

No SO₃ was indicated in the dissociation of alunite. The sulfate ion appears to dissociate by at least two different mechanisms although the parameter which controls the mechanisms has not been elucidated.     

Laser flash photolysis of iodine-iodide mixture in hydroxylic solvent. Evidence for the existence of the radical anion I

The laser flash photolysis of iodine-iodide mixtures in alcoholic solvents produces transient species absorbing in the red and near infrared region with maxima at 740 and 590 nm. The 740 nm absorption band has already been attributed to the well known I

ion. In this work the 590 nm absorption band is assigned to the I

radical anion which presumably could be formed by the equilibrium reaction: I

+ I₃^- ? I

. The variations of the intensities of the 590 and 740 nm transient absorption bands as a function of I₃^? concentration, temperature and solvent, support this assignment. The kinetics of formation of I

and I

has been studied in solutions of tertiary butanol. An analysis of the experimental results shows that the I

ion could be formed via a mechanism involving an I

intermediate.     

Gas phase electron diffraction study of tetravinyltin Sn(CHCH2)4

The tetravinyltin molecule has been studied by gas phase electron diffraction. The r_a structure analysis is based on the assumptions that a single conformer occurs in Sn(CHCH₂)₄ and that tin has a tetrahedral bond configuration. The preferred model (S₄ symmetry) predicts all four vinyl groups to be intermediate between staggered and eclipsed conformations. The structure refinement gives the following parameters (bond lengths, r_a, in nm, valence angles in degrees):

, SnCC = 121.9(0.6), CC = 0.1349(8), SnCH = 116.8(4.5),<C—H?_av. = 0.1098(14). The uncertainties given in parentheses represent three times the standard deviation values.The observed shortening of the

bond in Sn(CHCH₂)₄ from

in SnMe₄ (by 0.0027 nm) is equal to the shortening that occurs on going from

in ethane to

in propylene. With the corresponding Si and Ge derivatives, this effect is less pronounced.     

Some chlorine fluorosulfonate and peroxydisulfuryl-difluoride reactions

Chlorine fluorosulfonate adds exceptionally easy not only to various alkenes, perfluorobenzene, but to alkynes too

The addition of peroxydisulfuryldifluoride to alkyl- and perfluoroalkyliodides leads to unstable adducts, which decompose with the formation of alkylfluorosulfonates and iodine fluorosulfonate; the latter was trapped with fluoroalkenes

The use of ClOSO₂F allows to substitute selectively for the fluorosulfonate group the chlorine atom in monochloroacetic acid esters as well as the fluorine atom in hexafluoroacetone N-fluoroimine

ClOSO₂F serves as an exceptionally active chlorinating reagent for fluorinated alcohols, nitrosocompounds, perfluoroacid amides and particularly for benzene

The reaction of (OSO₂F)₂ with perfluoroacid amides leads to the corresponding N,N-bis(fluorosulfonate)amides, which easily rearrange into alkylfluorosulfonates

The hypochlorites of fluorinated alcohols are stable enough and they, similarly to ClOSO₂F, are able to add to alkenes, fluoroalkenes (but not to perfluoroisobutylene), bis(trifluoromethyl)ketene, trifluoromethylisocyanate and perfluoronitriles

The fluorosulfonatoacetic acid esters are unstable at the ambient temperature, but they can be widely used in situ as a very effective alkylating reagents

     

Synthese de la phenyl-2-dimethyl-4,5-phosphorine a partir du benzyl-1-dimethyl-3,4-phosphole

1-Benzyl-3,4-dimethylphosphate

-$\text{1}$ is converted into 2-phenyl-4,5-dimethyl-λ₃-phosphorin

-$\text{2}$ through 1,2-dihydro-λ₅-phosphorines

$\text{3}$ and

$\text{s}$.     

ESR spectra and electronic structure: some recent examples.

Results of ESR studies are presented for a number of radical ions selected from several classes of compounds of current interest. The strikingly different hyperfine data for the radical cations of 1,6:8,13-propane-1,3-

and 1,6:8,13-ethane-diylidene-[14]annulene

demonstrate the effect of an interplay of homoconjugative, inductive and hyperconjugative perturbations. The unusually stable radical cations of N,N′-dimethyl-

and N,N′-trimethylene-1,6:8,13-bisimino[14]annulene

should be regarded as N-centered radicals with an N-N 3-electron σ-bond. Despite similar geometries of [2.2]paracyclophane

, its 1,1,2,2,9,9,10,10-octa-fluoro-derivative

and its 1,9,-diene

, the corresponding radical anions strongly differ in their electronic structure. An unexpected conformatinal interconversion is observed for the radical anion of

. Electron acceptors, such as tetracyanoquinodimethane (TCNQ;

) and its areno analogues, and electron donors, represented by tetrathiafulvalene (TTF;

) and compounds containing the TTF system, form salts exhibiting high electronic conductivity (“organic metals”). ESR spectra of the radical anions and trianions of these acceptors and the radical cations of these donors provide detailed information about the spin distribution in the respective species.     

Sussex-N.P.L. computer analysed thermochemical data: Organic and organometallic compounds : J.B. Pedley and J. Rylance,University of Sussex, 1977 £10.00

The formation of new

intermediates and especially germaimines R₂GeNR′ has been observed in the reaction of germylenes with phenyl azide (precursor of phenylnitrene). These transient derivatives lead, by polycondensation reactions, to the corresponding cyclic or linear germazanes

, and are characterized by insertion reactions into the germanium—nitrogen bond, cleavage and addition reaction with tetrahydrofuran, and pseudo-Wittig reactions with benzaldehyde. The latter produces the corresponding germoxanes via new

intermediates and phenyl benzaldimine.     

Doping-addition of arylsulfenyl chlorides to the tricyclo[4,2,2,02,5]deca-3,7,9-triene system: skeletal rearrangements and serendipitious products

“doping-addition” of 2-NO₂C₆H₄SCl to the tricyclo[4,2,2,0^2,5]deca-3,7,9-triene system

occurs to give unusual products: (i) rearranged caged cyclopropane

and (ii) the stable cross-perchlorate

.     

Electrogeneration of triplet states of intramolecular anthracene-amine systems

In the electron transfer between the cation radicals

of the amine moiety of four intramolecular anthra cene-amine systems and the anion radicals B^XXX of some heterocyclic and carbonyl compounds in acetonitrile/toluene, the triplet state of the anthracene moiety

is formed. As intermediates in this process, intramolecular and intermolecular triplet exciplexcs

or

and

or

are discussed.     

The preparation of perfluorinated esters of fluorine containing tertiary alcohols

The reaction of an aromatic lithium reagent, LiR, with a perfluoroacid anhydride (RfCO)₂O, in ether solution at low temperatures, produces esters of composition

in addition to the expected ketone

. Mixed esters of composition

may be prepared by starting with a ketone

and reacting with a lithium reagent LiR followed by perfluoroacid anhyride (RfCO₂O. Hydrolysis of the esters provide a convenient route to trertiary alcohols of composition Rf(R) ₂COH.     

The third-order dynamic electric susceptibility of the hydrogen molecule

The dynamic third-order electric susceptibility of the hydrogen molecule has been computed. The results were obtained using the random-phase approximation, and for the parallel component give

= 702 au. This compares well with the experimental value of

= 777 ± 10 au.     

Dissociation of uranium(III) and uranium(IV) borohydrides in solution: 11B, 1H NMR study

Uranium(III) borohydride, which can be prepared in THF solution, and uranium(IV) borohydride are found to undergo dissociation to give cationic and anionic species:

these species are identified by their ¹H and ¹¹B NMR spectra. BH^?₄ is found to be in exchange between the three species in both cases.     

Synthesis and intramolecular charge-transfer interaction of o-tropyliobiphenyl tetrafluoroborates

A series of o-tropyliobiphenyl tetradfluoroborates

has been synthesized. Evidences are presented to show that

exhibit strong intramolecular charge-transfer interaction between tropylium ion and remote aryl ring. The structure of

was determined by single crystal X-ray diffraction study.     

The thermal decomposition reactions of [Co(en)3](NO3)3 and [Co(en)3](HSO4)3

The thermal decomposition reactions were determined for [Co(en)₃](N0₃)₃ and [Co(en)₃(HSO₄)₃ in a dynamic nitrogen gas atmosphere and _vacuo, where en represents ethylenediamine. Data were obtained using thermogravimetry, DTA, thermomagnetic analysis, and mass spectrometry. The dissociation reactions in nitrogen were found to be as follows:

and

In vacuo, the dissociation process for [Co(en)₃](N0₃)₃ is the same as in nitrogen. Also, the decomposition of [Co(en)₃](HSO₄)₃ is the same except for the first step which is:

     

Vibronic interaction between nπ and ππ states and phosphorescence of Norharmane

Solvent effects on phosphorescence and excitation spectra and its polarization characteristics indicate that the two major spin-orbit coupling mechanisms through which the ³ππ^* state of Norharmane acquires dipole-allowed character via nπ^* states are: