Phenyl Bonds Research Articles

Tin-119 Mössbauer and nuclear magnetic resonance studies of organotin compounds. Part 2. Sterically crowded organotin halides and carboxylates

Tin-119 Mossbauer and 119Sn NMR data have been obtained for a number of novel organotin halides and carboxylates containing bulky organic ligands (adamantyl, triptycyl). The Mossbauer spectra are discussed in terms of distortions from tetrahedral geometries as a result of steric crowding. The largest distortions occur for the adamantyl derivatives. A detailed study of 119Sn NMR shifts revealed correlations with Mossbauer quadrupole splittings and with the electronegativities of the ligands concerned. The crystal structure of (E)-(but-2-enyl)triphenyltin was determined: triclinic, space group P, with a= 9.892(3), b= 10.196(4), c= 11.637(5)A, α= 107.16(2), β= 103.40(2), γ= 109.77(2)°. The crystals are composed of discrete non-interacting molecules. The structure was refined to R= 0.035 and R′= 0.043. The geometry around the tin centres is only slightly distorted from tetrahedral with bond angles ranging between 107.5(2) and 112.8(2)°, average 109.5°. The Sn–C(but-2-enyl) bond is significantly longer than the three Sn–C(phenyl) bonds. The structure is compared to those of other similar compounds.

Darstellung neuartiger monomerer, oligomerer und polymerer Silyltriflate

Preparation of New Monomeric, Oligomeric, and Polymeric Silyl TriflatesThe highly reactive silyl triflates R3SiOSO2CF3 are valuable reagents in organosilicon chemistry. New triflate derivatives of mono‐ and oligosilanes have been prepared by substitution of phenyl groups or hydrogen atoms for the trifluoromethanesulfonyl group. The presence of the electron‐withdrawing triflate group leads to a strong deactivation of the other substituents at the silicon atom, and the displacement of a second phenyl group at the same silicon atom is much slower than the first step. For this reason in the case of phenylated oligosilanes stepwise monosubstitution of the silicon atoms has been found. Other new oligomeric silyl triflates are obtained by reaction of silanediyl(triyl) bis(tris)(trifluoromethanesulfonates) with lithium derivatives of organosilicon compounds. Finally, the cleavage of silicon–phenyl bonds of poly[methyl(phenyl)silanes] by CF3SO3H leads to triflate derivatives of polysilanes.

Zur synthese funktionel substituierter polysilane mittels trifluormethansulfonsäure

The cleavage of silicon phenyl bonds in phenylmethylpolysilane by CF 3SO 3H leads to triflate derivatives of polysilanes. The polymers react with lithium derivatives or acidic element hydrogen compounds under formation of numerous substituted polysilanes.

Configurational and conformational characteristics of the diastereoisomers of bis(o-chlorophenyl) 2,4-dimethylglutarate

The meso and racemic isomers of bis(o-chlorophenyl) 2,4-dimethylgutarate, which can be considered the dimer analogous of isotactic and syndiotactic poly(o-chlorophenyl acrylates, respectively, are isolated. Their mean-square dipole moment were measured in benzene solution and analyzed to obtain information on the statistical weights, which account for the two possible rotational angles about the Cα-CO bonds, and the value of the rotational angle about the ortho phenyl bonds

The crystal structure of triphenyl( N,N-diisopropyldithiocarbamato)tellurium(IV), an unusual dimeric structure

The crystal structure determination of Ph 3Te[S 2CN(i-Pr) 2] indicates a most unusual dimeric structure in which the ligand can be considered as acting as a bridge with very long TeS bonds. The crystals are triclinic in space group P 1 with cell parameters a 12.101(3) Å, b 8.728(2) Å, c 12.301(2) Å, α 80.88(2)°, β 102.60(2)°, γ 106.21(2)°, V 1210.9(5) Å 3, Z = 2, R = 0.0267, R w = 0.0340. The immediate environment about each tellurium atom can be described as that of a distorted octahedron. The three TeC (phenyl) bonds are mutually cis with two long TeS bonds of similar length and a lone pair completing the octahedron.

Dielectric Properties in the Nematic and Isotropic Phases of Di-n-Propyloxyazoxybenzene (3.OAOB) and Di-n-Pentyloxyazoxybenzene (5.OAOB)

Abstract Results of dielectric relaxation studies of two members of 4, 4′-n-alkoxyazoxybenzene homologous series, 3.OAOB and 5.OAOB, are presented. On the basis of dielectric spectra obtained for parallel (ε∥*) and perpendicular (ε⊥*) orientations of the samples with respect to measuring electric field the following problems are discussed: (i) the sign change of dielectric anisotropy when frequency increases from radio to microwave range; (ii) influence of the local field factor on the dipole correlation time in the nematic phase, and (iii) mechanism of molecular reorientations taking into consideration the dielectric spectra of three substances having different electric structures. It was concluded that the main molecular process contributing to the high frequency dielectric spectra of the nematic phases is the reorientation around the long axis of molecule as a whole, characterized by the relaxation time τ⊥ DR ≅ 85 ps, whereas the QNS method reflects the internal reorientations of two molecular moieties around N—phenyl bonds with the correlation times τQNS = (4 ÷ 9) ps.

ChemInform Abstract: Synthesis and Some Reactions of a 2,2′‐Biphospholyl.

AbstractThe biphospholene (I) is converted to the biphosphole (III) by bromination and subsequent dehydrobromination.

ChemInform Abstract: THE MOLECULAR STRUCTURE OF P‐BIS(TRIMETHYLSILYL)BENZENE FROM GAS PHASE ELECTRON DIFFRACTION

Abstract Nearly regular tetrahedral silicon bond configuration and a considerably distorted ring characterize the p -bis(trimethylsilyl)benzene molecular geometry according to an electron diffraction study. The SiC methyl bond is longer than the SiC phenyl bond, in agreement with expectation but contrary to an X-ray diffraction determination. The extent of ring deformation is consistent with the electropositive character of the trimethylsilyl substituent and with the structural variations in other para -disubstituted benzene derivatives. The electron diffraction data are consistent with either free rotation around the SiC phenyl bonds or with a rotamer deviating by about 15° from the eclipsed form. The following bond lengths ( r g , pm) and bond angles (°) have been determined with parenthesized estimated total errors: (CC) mean 140.8(3), (C ipso )(C ortho C meta ) 1.6(7), (SiC) mean 188.0(4), (SiC methyl )(SiC phenyl ) 3.3(7), (CH) methyl 111.3(3), CC ipso C 115.7(6), and C phenyl SiC methyl 109.2(4).

Chemie polyfunktioneller liganden : XLVII. Über die selektive spaltung von arsen—phenyl-bindungen mit bromwasserstoff in nichtwässrigen systemen

Zusammenfassung The phenyl- and phenylalkyl-arsines As(C 6 H 5 ) 3 , CH 3 As(C 6 H 5 ) 2 , C 2 H 5 As-(C 6 H 5 ) 2 , CH 2 [As(C 6 H 5 ) 2 ] 2 and CH 3 C[CH 2 As(C 6 H 5 ) 2 ] 3 react with HBr in nonaqueous solvents by selective cleavage of the arsenic—phenyl bonds yielding AsBr 3 ,CH 3 AsBr 2 ,CH 2 (AsBr 2 ) 2 and CH 3 C(CH 2 AsBr 2 ) 3 . The electron impact mass spectra of these compounds show clear fragmentation patterns resulting mainly from the formation of fragments with As—As bonds or As 3 clusters. The infrared and Raman spectra of all the alkylbromoarsines can be assigned completely in the range of 4000–30 cm -1 .

Conversion of bonded cyclo-octadiene into a cyclo-octadienyl ligand and cleavage of boron–phenyl bonds of arene-bonded tetraphenylborate anions in ruthenium(II) systems: X-ray crystal and molecular structures of [Ru(η6-C6H5BL3)(1–3,5,6-η-C8H11)](L = Ph or F)

Labilisation of the hydrazine ligands in either [Ru(cod)(N2H4)4][BPh4]2(I; cod = cyclo-octa-1,5-diene) or [RuH(cod)(NH2NMe2)3][BPh4](II) in acetone produces [Ru(η6-C6H5BPh3)(1–3,5,6-η-C8H11)] which reacts with HA (A = BF4 or PF6) to give [Ru(η6-C6H5-BF3)(1–3,5,6-η-C8H11)]; a byproduct of the reaction with (II) is [Ru(cod)(C6H6)].

Die komplexchemie polyfunktioneller liganden : XXVIII. Über die selektive spaltung von arsenphenyl-bindungen mit jodwasserstoff in nichtwässrigen systemen

The phenylalkyl arsines (CH 3) 2AsC 6H 5, CH 3As(C 6H 5) 2, C 2H 5As(C 6H 5) 2, (CH 2) n [As(C 6H 5) 2] 2 ( n = 1, 2), and C[CH 2As(C 6H 5) 2] 4 react with liquid or gaseous HI in nonaqueous solvents by selective cleavage of the arsenicphenyl bonds yielding (CH 3) 2AsI, CH 3AsI 2, C 2H 5AsI 2, (CH 2) n (AsI 2) 2 and C(CH 2AsI 2) 4. The latter forms the tetradentate ligand C[CH 2As(CH 3) 2] 4 with CH 3MgI. The electron impact mass spectra of these compounds show clear fragmentation patterns resulting mainly from the formation of fragments with AsAs bonds or (As) n clusters ( n = 3, 4). From CH 3AsI 2 and C 2H 5AsI 2 the iodine-free cycloarsines (AsCH 3) 3, (AsC 2H 5) 3, (AsC 2H 5) 4, As 3(C 2H 5) 2CH 3 and As 4(C 2H 5) 3CH 3 are formed by thermal secondary reactions in the high temperature inlet systems of the mass spectrometer. The fragmentations of the cycloarsines and the other compounds are discussed. The infrared spectral absorptions of all the alkyl iodoarsines can be completely assigned in the range of 4000 – 250 cm −1. The IR data of C 2H 5AsI 2 indicate the existence of trans and gauche rotational isomers.

Thermal degradation of polymers. II. Mass spectrometric thermal analysis of phenol‐formaldehyde polycondensates

AbstractThe degradation of phenol–formaldehyde polycondensates has been investigated by mass spectrometric thermal analysis to 800°C. The thermal oxidative mechanism proposed by Conley and co‐workers has been confirmed. Direct analysis of products at frequent intervals of a temperature‐programmed heating cycle demonstrates the existence of postcuring, general degradation, and char‐forming stages. Activation energies for formation of each product and for degradation of the polymer have been determined. Phenolic homologs, products of thermal scission of methylene–phenyl bonds, show high activation energies; oxidation products have activation energies comparable to or slightly higher than that for oxidation of methylene bridges to carbonyl groups. The tarry high molecular weight products found on pyrolysis at atmospheric pressure are not formed in high vacuum because recombination reactions of phenols and formaldehyde are minimized. Otherwise, no major change in product composition, as compared to the high heating rate pyrolysis–gas chromatographic investigation of Jackson and Conley, was observed.

THE INFRARED AND THE NEAR-ULTRAVIOLET ABSORPTION SPECTRA OF POLYPHENYL DERIVATIVES OF THE ELEMENTS OF GROUPS IVb AND Vb

The near-ultraviolet absorption spectra of polyphenyl derivatives of the IVb and Vb elements have been studied in detail. In the case of the triphenyl derivatives of the Vb elements, the unshared p-electrons on the central atoms interact strongly with the π-orbitals of the benzene rings. When the central atoms do not possess unshared electrons as in the case of the derivatives of the IVb and the pentavalent Vb elements, there appears to be no such resonance interaction. The Hammett reactivity constants of the para- and meta-trityl, triphenylsilyl, and triphenylgermanyl groups are estimated to be close to zero. However, the reactivity constant of the triphenylsilyl group in the para position of phenol is estimated to be about 0.30. The infrared spectra of the phenyl derivatives of the IVb and Vb elements show smooth trends due to mass effects of the central atoms, in the C=C skeletal, C—H out-of-plane, and other vibrations. The absorption frequencies which are assigned to the phosphorus-phenyl and silicon–phenyl bonds in the literature do not appear to be unique for these linkages.