Sensitized photochemical reactions of some silyl-1,3-butadienes: Synthesis of 2,2,4-trimethyl-3-methylene-2-silabicyclo [2.1.1]Hexane

The photolysis of 2,4,4-trimethyl-4-sila-3-methylene-l,5-hexadiene

yielded 2,2,4-trimethyl-3-methylene-2-silabicyclo[2.1.1]hexane as the only volatile photoproduct in high yield. However, 2,4,4-trimethyl-4-sila-3-methylene-1,6-heptadiene

was found to be photochemically non-reactive under identical reaction conditions, and the 1-substituted butadienes (VI) and (VIII)

underwent cis-trans isomerism on photolysis.     

Zur komplexchemie von 4-zentren-π-systemen : XII. Glyoxaldiiminkomplexe: 1H-nmr-spektren und long range-kopplungen

Glyoxaldiimines (I) RN=CHCH=NR show in the NMR a downfield shift of glyoxalic protons (H_gly) when complexed to

(II: M = Mo, W), but increasing high field shifts when going to

(III) and

complexes (IV). In the tungsten complexes II H_glyW coupling satellites are resolved (J(WH) ≈4–6 Hz); in the phosphine compounds III, IV long range PH_gly coupling is clearly visible. Mechanisms of spinspin interaction are briefly discussed in connection with the EPR results on monoanionic radicals of II–IV.     

Addition du di-t-butyl-zinc a la triple liaison des enynes conjugues,simples et fonctionnels

Di-t-butylzinc adds easily to conjugated enynes

. Only the acetylenic bond is involved in this reaction which proceeds via trans-addition. This regioselective and stereoselective addition leads to conjugated dienes

.     

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.     

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.     

On the Pauling electronegativity scales—I

It is shown that the Pauling electronegativity scale χ is closely related to the electrostatic potential near the physical meaningful boundary between the core and valence regions in an atom, and is well reproduced by the relationship:

where N_ν is the valence electron number and the factor f(n) is empirically given by

n being the periodic number.     

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

.     

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.     

Further evidence for the intramolecular charge-transfer interaction between tropylium ion and remote benzene rings in 9,10-dihydro-9,10-(1,2-tropylio)anthracene tetrafluoroborate and its methyl derivatives

A series of 9,10-dihydro-9,10-(1,2-tropylio)anthracene tetrafluoroborates

has been prepared. The intramolecular charge-transfer interactions in

were confirmed by their UV spectra and pK_R+ values. As a model compound 1,2,3,4-tetrahydro-1,4-(1,2-tropylio)naphthalene tetrafluoroborate ($\text{5}$)_was also examined.     

Etude en resonance magnetique nucleaire du carbone-13 de complexes η-1,5-cyclooctadiene β-dicetonato iridium(I)

The ¹³C NMR spectra of iridium complexes of 1,5-cyclooctadiene are reported and discussed. For compounds containing β-diketonato ligands, a correlation is found between the ethylenic carbon chemical shifts and the Swain and Lupton

and

values of the substituents of the β-diketonato ligand. The relationship is satisfactorily explained by considering the Dewar, Chatt and Duncanson model of bonding. Tentative interpretation of the observed chemical shifts of the other carbons is presented.     

Evidence for the direct isomerization of a platinocyclobutane to an olefin complex

Dichloro-2,3,3-trimethyl-1-platinocyclobutane,

, prepared by the metathetical reaction of Zeise's dimer and 1,1,2-trimethylcyclopropane, reacts with pyridine in chloroform to produce a platinum complex of 2,3-dimethyl-1-butene

. Reaction of I with pyridine at low temperatures (ca. ?40° C) leads to a pyridine addition compound (III) in which the platinocyclobutane ring remains intact. The thermal isomerization of III, which may be conveniently studied using NMR, produces a mixture of II and the free olefin.     

Electrokinetic phenomena in porous membranes: Determination of phenomenological coefficients and transport numbers

Electrokinetic phenomena in porous membranes were studied in the framework of the linear thermodynamics of irreversible processes. Phenomenological coefficients of two commercial porous membranes were determined. The variation of these coefficients with the different concentrations of NaCl used was also studied. Onsager's reciprocal relationship between cross-coefficients holds within the limits of experimental error.Membrane potentials were measured at concentrations ranging from 10^?3M to 75 X 10^?3M. The apparent transport number of the cation,

, was calculated from the diffusion potential expression. An electrometric method was used to obtain the true cation transport number,

, and the water transport number,

, for different solution concentrations, ranging from 15 x 10^?3M to 75 x 10^?3M. The true transport number of the cation,

, was also determined, taking into account water transport across the membrane. A good agreement was found between

and

values.     

The reaction pathway from Speier's to Karstedt's hydrosilylation catalyst

Multinuclear, variable temperature NMR spectroscopic experiments show that: (i) treatment of

, 1, with an excess of (CH₂=CHSiMe₂)₂O (≡ LL) yields

, 2; (ii) treatment of 1 with PhCH=CH₂ gives

3; and (iii) reaction of cis-[Pt(ν²-CH₂=CHPh)Cl₂] with LL yields successively 1, 2, and 3. The pathway in case of (iii) involves initial chloride-vinyl exchange, followed by reductive elimination in which vinyl radicals and vinyl chloride may be involved.     

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

$\text{s}$.     

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

     

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.     

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.     

η2-acylcarbonylvanadium-verbindungen

Substituted vanadium carbonyl compounds with η²-bonded acyl ligands (η²-RCO)V(CO)₃

(

= ditertiary phosphines or arsines: dppe, dppp, dppm, diars, arphos, dpase) have been prepared by photochemical reaction of [V(CO)₄

] with various substituted benzoyl chlorides and cyclopropanylcarbonyl chloride.Effects of aromatic substituents and

upon the thermal stability of the η²-acylcarbonylvanadium compounds are discussed. IR ν(CO) force constants and ⁵¹V NMR signals are linearly correlated with Hammett's σ constants of the aromatic substituents.The preparation of V(CO)₂Cl(diars)₂ is described.     

cis-Dichloro {BIS-1-anti, 3-syn-(o-diphenylphosphino)phenyl-1-methallyl(1-3η) } rhodium(III): a chelate π-allylic complex formed by proton abstraction from an olefinic di-tertiary-phosphine)

The preparation, properties, and single crystal X-ray structure of the title complex,

are described.     

Effective stereoselective approach to substituted 1,4-dioxane-2,5-diones as prospective substrates for ring-opening polymerization

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