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.     

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.     

Peroxo compounds: Part XVI. Electron diffraction investigation of the molecular structures of di-t-butyl peroxide Me3COOCMe3 and bis(trimethylsilyl) peroxide Me3SiOOSiMe3

The molecular geometries of Me₃COOCMe₃ and Me₃SiOOSiMe₃, in the gas phase were determined by electron diffraction. For the skeleton of di-t-butyl peroxide the following geometric parameters (r_a-values) were obtained: r(O—O) = 1.480 Å (assumed),

. This dihedral angle is compared with the results of IR and Ram an spectroscopy, dipole moment measurements and photoelectron spectroscopy. The main geometric parameters for bis(trimethylsilyl) peroxide are

. For both peroxides SCF-MO calculations in the CNDO/2 approximation do not reproduce the experimental results.     

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.     

Synthese de composes a liaison MIVBmercure. Precurseurs d'especes monovalentes (germynes), et bivalentes (germylenes), de radicaux centrometalles et d'intermediaires

Polynuclear germylmercury compounds are obtained from the reaction of organohydrogermanes Ph_nGeH_4?n or digermanes Ph_2nGe₂H_4?n (n = 1, 2) with dialkylmercury R₂Hg. Di- or tri-mercurated geminal polygermates thus synthesized generally present a low stability and undergo thermal- or photo-decompositions leading to the corresponding monovalent (germynes), divalent (germylenes) or, trivalent (germanium centered radicals) species and also to intermediate

biradicals which could be considered as limit forms of germanium doubly-bonded compounds

. Such intermediates have been chemically and spectroscopically characterized.Extension of these reactions to the silicon analogs met with difficulties, and thus previously observed differences between silicon and germanium chemistry were confirmed.     

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

.     

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.     

Metalmetal bonded triazenido compounds : II. Compounds with M = RhI,IrI; R = Me,aryld and X = Cl,Br, I Cl,Br, I

Complexes

(M = Rh, X = Cl, M = Ir, X = Cl, Br, I and R = CH₃, R′ = CH₃, p-tolyl) have been made by the reaction of (Ph₃P)₂(CO)MX with

. The proposed structure is analogous to that of the related copper derivatives and contains a five-membered ring in which an M^I to Ag^I donor bond is bridged by an azenido group, while the halide atom X has migrated from M^I to Ag^I.Carbon monoxide at 1 atm reacts rapidly and quantitatively with the iridium compounds to give novel acyltriazenido compounds {Ph₃P(CO)₂ - Ir[OCN(R)N=NR′]} (R = CH₃, p-tolyl; R′ = CH₃, p-tolyl).     

Stannoboroxanes : III. Synthesis and reactions of 1,3-bis(boryloxy)tetraalkyldistannoxanes and related compounds

1,3-Bis(boryloxy)tetraalkyldistannoxanes,

, R = Me, Bu; G = CMe₂CH₂CHMe—, —CMe₂ —CMe₂ — and —CHMe—CH₂ — have been prepared from dialkyltin oxide and pyroborate, or directly from dialkyltin oxide, boric acid and glycol. A dimeric structure for these compounds is proposed on the basis of molecular weight, IR and PMR studies. The reactivity of the SnOB bond towards PhNCO and Me₃SiCl has been demonstrated.     

The 2,2 dialkyl-1,3,2 dioxastannoles and their telomerization reactions with dialkyltin oxides

Benzoin readily reacts with dibutyltin oxide to give the 1,3,2-dioxastannole (A) and thence the dialkylstannoxane oligomers (B) (n  0–9)

1,3,2,-Dioxastannoles (I) have been reported to be formed when transient (R  Bu) [1] or isolable (R  Me₂NCH₂CH₂O) [2] tin(II) compounds react with benzil (eq. 1).

We report here a simple new route to the 1,3,2-dioxastannoles, and some of their properties, particularly their telomerization with dialkyltin oxides.If, for example, dibutyltin oxide and benzoin are heated in benzene under a Dean and Stark water separator, the benzoin behaves as an enediol, and the dialkyltin oxide dissolves in about 1 h to give 2,2-dibutyl-4,5-diphenyl-1,3,2-dioxastannole (II), which is very soluble but can be isolated from pentane at low temperature as an amorphous power (see scheme 1).     

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.     

Etude de la structure de carbanions en α du soufre

Carbanions α to sulfoxides and sulfones C₆H₅S(O)nCH₂M (n  1, 2; M  Li or K) have been studied by infrared and Raman spectroscopy. A strong increase of the force constant of the SCH₂M bond, and a similar decrease of that of the SO bond(s) are observed. This implies that the negative charge is delocalized over the carbon and oxygen atoms. ¹H NMR shows that carbanions α to sulfoxides are configurationally stable at low temperature. The interconversion energy depends on the polarizing ability of the counter-ion (Li⁺: ΔG

13.6 kcal mol^-1; K⁺: ΔG

10.7 kcal mol^-1). The coupling constant of the methylenic hydrogens (J_AB 2 Hz) confirms the nearly planar configuration of the anionic carbon in the α metallated sulfoxides.     

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

.     

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

Tautomerism in the system

has been observed for the first time.     

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.     

Réactions des céténes et du dicéténe avec les germyl- et silylphosphines

Ketenes add to germyl- and silylphosphines R₃MPEt₂ with opening of the carbonyl group and formation of phosphorylated alkenoxygermanes or -silanes

(R′H, Ph). These adducts are thermally stable and only the addition derivative of diphenylketene and Me₃SiPEt₂ exhibits metallotropic isomerization to a C-derivative after prolonged heating. Hydrolysis of these addition compounds is a new approach to the acylphosphines R₂CH-CO-PEt₂. Diketene also reacts with germyl- and silylphosphines with acyloxygen bond cleavage and formation of metallated and phosphorylated ketoenolates of the type

. These derivatives isomerize either partially (MSi) or completely (MGe) into R₃MOC(CH₃)CHCOPEt₂. Their hydrolysis constitutes a new method of synthesis of the phosphorylated β-diketone

. The ketoenolates from the addition reaction of the hydrosilylphosphine, Me₂Si(H)PEt₂, cyclize readily after partial isomerization by the intramolecular addition SiH to CO, to give phosphorylated siladioxane and siladioxene. The conformation of these heterocyclic compounds has been studied.     

Zur ursache der extremen 31P-NMR-verschiebungen von phosphinidenkomplexen

Phosphinidene complexes RP[ML_n]₂ (R = univalent residue; L_nM = 16 electron fragment e.g. (CO)₅Cr, Cp(CO)₂Mn) show extremely paramagnetic ³¹P NMR shifts (884 to 1362 ppm). The values of these NMR shifts are strongly correlated with the energy of the electroic ππ^* transition in

π-systems. The large paramagnetic ³¹P NMR shifts is caused by the small

HOMO-LUMO separation specific for these compounds.     

Organoboron compounds: XXVII. A13C NMR Study of PhB(NMe2NHBut and PhB(NMe2)NHSiMe3

The rotational barriers (ΔG) about the

bond in PhB(NMe₂)NHBu^t and PhB(NMe₂)NHSiMe₃ have been determined by variable temperature ¹³C NMR.     

Organoboron compounds XIII. Preparation and properties of some 2-substituted 1,3,2-dithiaborinans

The preparation and properties of some boron heterocycles of the general formula

(where X = Ph, SR, NR₂, NHR and NHNPh) are described and the general features of their mass spectra discussed.     

N-alkyl- and N-aryl-thioformamido complexes of the platinum group metals

Alkyl- and aryl-isothiocyanates undergo insertion reactions with platinum metal hydrides to yield the corresponding N-alkyl- and N-aryl-thioformamido

derivatives, the structure and stereochemistry of which have been deduced using ¹H NMR data.