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.     

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.     

Preparation and properties of some cyclic germanium 1,4-cyclohexanediolates

Colourless liquids of cyclic compounds of the type:

have been prepared by reactions of dibutylgermanium dichloride with cis-1,4-cyclohexanediol or cis,cis,cis-2,5-di-tert-butyl-l,4-cyclohexanediol, in benzene in the presence of a hydrogen halide acceptor.Under similar conditions germanium tetrachloride gave solid products of the type:

Physical and spectroscopic data (IR, Raman, and MS) are given and discussed.     

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.     

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.     

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

.     

Nature of the hydrogen bridge in transition metal complexes: II. Molecular orbital calculations of binuclear carbonyls of Mn,Re, Cr,Mo and W with double hydrogen bridges

To throw more light on the nature and character of the metalhydrogenmetal bond we carried out the electronic structure calculations by use of the parameter-free Fenske-Hall method and the semi-empirical EHT method for

complexes (M = Mn, Re, Cr, Mo, W and n = −2,0). The character and stability of the double hydrogen bridges in these complexes and in

and

were compared. The effects that type of transition metal has on the character and stability of double hydrogen bridges in carbonyl dimers are described. The electronic structures of the bridge cores in the double-and single-hydrogen bridge binuclear carbonyls of chromium and molybdenum were compared.     

Niederkoordinierte phosphorverbindungen: LIII. 1,3-Diphosphaallyl-nickelkomplexe

(R = 2,4,6-tri-t-butylphenyl) and

(R = 2,4,6-tri-t-butylphenyl) are two new nickel complexes with a 1,3-diphosphaallyl ligand. Both structures have been determined by X-ray analysis.     

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.     

Übergangsmetall-carbin-komplexe : XVI. π-Cyclopentadienyl(dicarbonyl)carbin-komplexe des wolframs

Tautomerism in the system

has been observed for the first time.     

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

.     

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.     

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.     

Synthesis of (±)-lineatin,the unique tricyclic pheromone of Trypodendron lineatum (olivier)

(+-)-3,3,7-Trimethyl-2,9-dioxatricyclo[4.2.1.0^{4, 7}]noname

and (+-)-3,3,7-trimethyl-2,9-dioxatricyclo[3.3.1.0^{4, 7}] nonane

were synthesized. The latter was shown to be (+-)-lineatin, an ambrosia beetle pheromone.     

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

).     

Activation catalytique des réactifs de grignard par les complexes du nickel en sèrie organosilicièe : II. Rèduction des organosilanes fonctionnels avec les rèactifs de grigrand saturès

A silicon deuteride DH exchange reaction demonstrates the reductive characteristics of saturated Grignard reagents catalytically activated by nickel complexes. Application of this reaction to the organosilanes R₁R₂R₃SiX(X=OCH₃,F,Cl) provides a new method for their reduction.

The reduction takes place with retention of configuration at the silicon atom for methoxy. and fluorosilanes. However inversion of configuration occurs in the case of chlorosilanes.The new type of reaction can also be used for the reduction of vinylsilanes

The results show the reductive properties of the Ni-H bond formed by β-elimination of the Ni-R intermediate.     

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 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.     

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.     

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