Showing papers on "Lewis acids and bases published in 1978"
TL;DR: A review of the current status of the Lewis acid-base definitions as a systematizing tool in chemistry can be found in this article, where the main concern is with the nature of the definitions themselves, their range of application, their limitations, the clarification of interpretive or semantic problems.
Abstract: This is not so much a proper review, in the sense of being a detailed survey of current experimental work, as it is a retrospective essay on the current status of the Lewis acid-base definitions as a systematizing tool in chemistry. Indeed, as the main concern is with the nature of the Lewis definitions themselves, their range of application, their limitations, the clarification of interpretive or semantic problems, etc., this essay might be most accurately characterized as a review of monographs and reviews which, in turn, deal with the raw experimental data. The Lewis definitions are now over a half-century old. To what extent has the work on organometallic compounds, for example, or on new nonaqueous or molten salt solvent systems, or the addition of new bonding concepts to the traditional two-center, two-electron bond and octet rule available to Lewis tended to repudiate or confirm the value of the Lewis definitions? It is hoped that this review will convince the reader that the devel-
254 citations
197 citations
Patent•
09 May 1978TL;DR: In this article, a radiation curable mixture of epoxy resin and di- or polyacrylate monomers in combination with a catalyst system comprising a carbonyl type photoinitiator with an aromatic onium salt capable of effecting the cure by release of a Lewis acid was described.
Abstract: This invention relates to radiation curable compositions comprising mixtures of epoxy resin and di- or polyacrylate or methacrylate terminated monomers in combination with a catalyst system comprising a carbonyl type photoinitiator with an aromatic onium salt capable of effecting the cure by release of a Lewis Acid.
113 citations
94 citations
TL;DR: The oxide form of the Co-Mo-Al2O3 system and its interaction with CO, H2O, thiophene, and pyridine have been studied by ir and electronic spectroscopy as mentioned in this paper.
92 citations
82 citations
Patent•
14 Jun 1978TL;DR: In this article, a titanium trihalide is ground with an organic Lewis base compound, which contains at least one phosphorus atom, and optionally one nitrogen atom and a titanium tetrahalide, and the materials are conveniently milled together and used as a component of an olefine polymerization catalyst.
Abstract: A titanium trihalide is ground with an organic Lewis Base compound which contains at least one phosphorus atom, and optionally at least one nitrogen atom, and a titanium tetrahalide, the Lewis Base and the titanium tetrahalide being used in amounts of 5 to 75, preferably 5 to 50%, molar and 1 to 50, preferably 5 to 30% molar respectively relative to the titanium trihalide. The materials are conveniently milled together and the milled product can be used as a component of an olefine polymerization catalyst and when such catalysts are used to polymerize propylene a high activity is achieved together with satisfactory stereospecificity.
56 citations
56 citations
TL;DR: In this article, the hydride-bridged complexes {[(π-C5H5)M(CO)3]2H}+X- have been obtained by reaction of σ-and π-donors L to give [(π-c5h5)(OC)3ML]+X- [L = CO, PPh3, PCl3, C2H4, CH3CN, H2O, (CH3)2CO, C4H8O(THF)].
Abstract: Hydride abstraction from the hydrides (π-C5H5)(OC)3MH (M = Mo, W) using Ph3C+X_ (X = BF4, PF6) affords the compounds (π-C5H5)(OC)3MX in high yields. IR data indicate that in these complexes tetrafluoroborate and hexafluorophosphate are coordinated to the metal. The complexes behave as strong Lewis acids; they react with σ- and π-donors L to give [(π-C5H5)(OC)3ML]+X- [L = CO, PPh3, PCl3, C2H4, CH3CN, H2O, (CH3)2CO, C4H8O(THF)]. The hexafluorophosphate compounds add methylene chloride to give [(π-C5H5)(OC)3M(CH2Cl2)]+PF6-. Reaction with diphenylacetylene yields [(π-C5H5)(OC)M(PhC ≡CPh)2]+BF4- (M = Mo, W). The hydride-bridged complexes {[(π-C5H5)M(CO)3]2H}+X- have been obtained by reaction of (π-C5H5)(OC)3MX with (π-C5H5)(OC)3MH.
50 citations
TL;DR: In this paper, a polyacetylene film has been oxidized with transition metal ions to give highly conducting polyolefinic cations; their conductivity can be modified by subsequent treatment with Lewis bases.
Abstract: Polyacetylene films have been oxidized with transition metal ions to give highly conducting polyolefinic cations; their conductivity can be modified by subsequent treatment with Lewis bases
47 citations
TL;DR: In this paper, 1,3-Diorganyl-2,2-dimethyl-I,3,2,4λ2-diazasilastannetidines can be prepared as monomers or dimers (organyl = tert-butyl) in nonpolar solvents, depending on the organic nitrogen substituent.
Abstract: Abstract 1,3-Diorganyl-2,2-dimethyl-I,3,2,4λ2-diazasilastannetidines can be prepared as monomers (organyl = tert-butyl) or dimers (organyl = isopropyl) in nonpolar solvents, depending on the organic nitrogen substituent. The formation of the dimer, which is due to an intermolecular Lewis-acid-base interaction of Sn(II) with nitrogen, can be initiated by solidification. When the tertf-butyl compound is cooled below 0 °C two crystalline modifications are found: a monoclinic phase (C 2/c; a= 10.655(5); b = 24.75(1); c = 17.334(9) Å; β = 106.9(1)°) and a triclinic phase (P1̄; a = 10.68(1); b = 13.51(1); c = 12.36(1) Å; α = 96.2(1); β = 102.6(1); γ = 118.4(1)°). The crystal structures turn out to be built of dimeric and monomeric units in the first case and presumably only dimeric species in the second case. The isopropyl derivative crystallizes in the space group P 21/b (a = 10.77(1); b= 12.14(2); c = 11.15(2) Å; β = 120.2(2)°) with only dimeric units being present, as in the liquid. Interrelationships between the three structures are discussed.
TL;DR: In this paper, the reaction of allylsilanes with α,β-unsaturated acetals in the presence of titanium tetrachloride afforded diallylated compounds, while monoallylated compounds were obtained selectively by the reaction promoted by aluminum trichloride or boron trifluoride-ether complex.
Abstract: The reaction of allylsilanes with α,β-unsaturated acetals in the presence of titanium tetrachloride afforded diallylated compounds, while monoallylated compounds were obtained selectively by the reaction promoted by aluminum trichloride or boron trifluoride–ether complex.
TL;DR: The reaction of allylsilanes with 1,1-dimethoxybutan-3-one was found to proceed selectively on the acetal moiety regardless of the kind of Lewis acid as discussed by the authors.
Abstract: The reaction of allylsilanes with 1,1-dimethoxybutan-3-one was found to proceed selectively on the acetal moiety regardless of the kind of Lewis acid, while the chemoselectivity of the corresponding reaction with 1,1-dimethoxypropan-2-one was changed dramatically by the sort of Lewis acid employed.
TL;DR: In this article, the first four of the new compounds listed are tentatively assigned monomeric structures, while the latter three are assigned oligomeric structure, and it is also possible to manipulate the degree of association of these species by control of the group 2B metal ion coordination sphere.
Abstract: CdFe(C0)4, and (4-C6HSC5H4N)CdFe(CO)+ Proper ligational strategy thus allows the isolation of several types of compounds which differ from the previously known B2CdFe(C0)4 and (NH3)3ZnFe(C0)4 patterns. It is also possible to manipulate the degree of association of these species by control of the group 2B metal ion coordination sphere. Thus the first four of the new compounds listed are tentatively assigned monomeric structures, while the latter three are assigned oligomeric structures. The present studies also reveal that A~CO(CO)~ is isomorphous with [CdFe(C0)4]4 and that (~y),CdFe(C0)~ exists as a trimer in the solid state. The complex (2,2’-bpy)AgCo(CO), is found to be at most partly associated in noncoordinating solvents. In the solid state, PbFe(CO)4 is associated. It has been known for some time that the metal-metal bonded oligomer [CdFe(C0)4],3 forms adducts, B2CdFe(C0)4, with a wide variety of Lewis bases, B.334 Until very recently there has been no structural information available for any of these materials. Diffraction studies have now shown that [CdFe(CO),], is a tetramer (n = 4) with approximately D4h symmetrysa and that (2,2’-bpy)CdFe(CO),, bpy = bipyridyl, is a trimer with approximately D3h symmetry.5b The molecular geometries of these compounds are illustrated in Figure 1. The structures of [CdFe(C0)J4 adducts with other Lewis bases remain largely undefined. The compound [HgFe(C0)4]4 is also known6,’ and is isomorphous with [CdFe(C0)4]4,sa but no base adducts have been isolated. In comparison to the results for cadmium and mercury, the only reported zinc-containing derivative, B3ZnFe(C0)4 where B = NH,,’ contains three molecules of base. Unlike the cadmium diammine, (NH3)2CdFe(C0)4, the zinc triammine does not readily lose ammonia on heating in V~CUO.~ A number of structural types are conceivable for the above Lewis base adducts, viz., A-C. In isoelectronic group 1B metal-transition
TL;DR: In this paper, qualitative observations on the catalytic activity of Lewis acids in converting ergosteryl acetate into its 5α,8α peroxide are presented, which is ascribed to complex formation between it and the Lewis acid catalyst.
Abstract: Some qualitative observations on the catalytic activity of Lewis acids in converting ergosteryl acetate into its 5α,8α peroxide are presented. The peroxide has an inhibiting effect on the reaction, which is ascribed to complex formation between it and the Lewis acid catalyst. This complex formation is used to explain the dual thermal and photochemical activity displayed by FeCl3 and MoCl5. A mixed oxygenation experiment with ergosteryl and lumisteryl acetates indicates that singlet oxygen is not an intermediate in this reaction. A model for the reaction, involving formation of a diene cation radical within a charge-transfer complex, is advanced.
TL;DR: In this article, a simple synthesis of 5-oxo-1,3λ4,2,4-dithiadiazole (S2N2CO, 1) is reported.
Abstract: Es wird eine einfache Synthese fur 5-Oxo-1,3λ4,2,4-dithiadiazol (S2N2CO. 1) beschrieben. 1 kristallisiert in der Raumgruppe Pbca-D und ist ein funfgliedriger planarer Ring. Reaktionen von 1 in CH2Cl2 mit den Lewis-Sauren A ergeben die Mono- und Bisaddukte S2N2CO · A und (S2N2CO)2 · A, wobei A = BF3 (2a), SO3 (2b), SbCl5 (2c), SbF2Cl3 (2d), SnCl4 (3a) und TiCl4 (3b) ist. IR- und Raman-Spektren werden mitgeteilt und mogliche Strukturen der Addukte diskutiert.
The Crystal Structure of 5-Oxo-1,3λ4,2,4-dithiazole, S2N2CO, and its Adducts with Lewis Acids
A simple synthesis of 5-oxo-1,3λ4,2,4-dithiadiazole (S2N2CO, 1) is reported. 1 crystallizes in the space group Pbca-D- and is a five-membered planar ring. Reactions of 1 in CH2Cl2 with the Lewis acids A yield the mono- and bisadducts S2N2CO · A and (S2N2CO)2 · A, where A = BF3 (2a), SO3 (2b), SbCl5 (2c), SbF2Cl3 (2d), SnCl4 (3a), and TiCl4 (3b). IR and Raman spectra are reported and possible structures of the adducts are discussed.
TL;DR: In this article, the reaction of 2H-azirines with nitriles in the presence of boron trifluoride etherate to yield the corresponding imidazoles is described.
Abstract: Acid-Catalysed Formation of Imidazoles from 2H-Azirines or Vinylazides and Nitriles
The reaction of 2H-azirines with nitriles in the presence of boron trifluoride etherate to yield the corresponding imidazoles is described. 2,3-Diphenyl-2H-azirine (10) gives 2-substituted 4,5-diphenyl imidazoles in moderate bis good yields (see Table 1). The reaction of 10 with acrylonitrile only leads to the formation of 4,5-diphenyl-2-vinylimidazole (17). No products resulting from an addition to the C,C double bond are observed. 2H-Azirine 10 and ethyl cyanoacetate yield the expected imidazole 18 (30%) but also 2-cyanomethyl-4,5-diphenyloxazole (20; 7%) (see Scheme 4). The yield of imidazole formation mainly depends on the substituents in position 2 of the 2H-azirines (see Scheme 6), a change of the substitutents in position 3 having only little influence. The best yields are observed with a phenyl group at C(2) of the 2H-azirines. These observations are in agreement with the occurrence of 1-azaallyl cations formed by ring opening of the 2H-azirines linked to the Lewis acid (boron trifluoride). Similar results are obtained with the corresponding vinyl azides with the exception of 1-azido-1-phenylethylene (28). Whereas the corresponding 3-phenyl-2H-azirine (24) gives 2,4-diphenylimidazole (33; Scheme 6) in the presence of benzonitrile and boron trifluoride etherate, the azide 28 yields only acetanilide (86%). In the presence of triethyloxonium tetrafluoroborate 2H-azirines and benzonitrile react to yield the corresponding 1-ethylimidazoles (see Scheme 9). This again demonstrates that 1-azaallyl cations must be intermediates which react with the nitrile presumably in a Ritter type reaction. 13C-NMR. spectra of 2H-azirines are also reported (Table 2).
TL;DR: In this article, an equation of the type log K, = EAEB + CACB, where E and C are identified with the tendency of the Lewis acid A and base B to undergo ionic and covalent bonding was used to correlate the F-, OH-, and NH, formation constants of 27 Lewis acids to a standard deviation of 0.24 log unit.
Abstract: It is shown that four-parameter equations proposed by previous authors have poor predictive powers for data of formation constants in aqueous solution. This relates partly to the paucity of data on complexes of ligands such as ammonia which, with most metal ions, cannot exist in water because of hydrolysis. Equations previously proposed that relate the formation constants of polyamine and poly(aminbcarboxy1ate) complexes to those of the ammonia and acetate complexes are used to calculate formatio‘n constants for these hydrolysis-prone ammonia complexes. An equation of the type log K, = EAEB + CACB, where E and C are identified with the tendencies of the Lewis acid A and base B to undergo ionic and covalent bonding, was used to correlate the F-, OH-, and NH, formation constants of 27 Lewis acids to a standard deviation of 0.24 log unit. Hardness parameters l!fA and HB were defined as EA/CA and EB/CB for acids and bases, respectively, and gave reasonable orders of hardness It was found that for ligands with large donor atoms, such as C1-, and for sulfur or phosphorus donor atoms, deviations from the predictions of this equation were observed that appeared to be related to the size of the acid, so that no deviations were observed for large cations such as Ag’ and Pb2+, aith Occurrence of large deviations for smaller cations such as Cu” or Ni2+, with the very largest occurring for the proton. These deviations were attributed to steric hindrance between the large donor atom and adjacent coordinated water molecules. The important contribution of the Edwards equation’ lies in illustrating that formation constant data for complexes of unidentate ligands in aqueous solution need at least a dualbasicity scale for any kind of correlation to be obtained at all. There have been several other multiparameter equation^^-^ proposed for correlating formation constant data. The need for at least a dual-basicity equation has manifested itself in the classification of metal ions’into Schwart~enbach’s~ and Ahrland and Chatt’s6 A- and B-type metal ions and Pearson’s more general classification7 of Lewis acids and bases into hard and soft acids and bases (HSAB). Drago and co-workers* have had considerable success with a more generalized form of a four-parameter equation similar to eq 1 for the correlation of enthalpy changes on adduct formation in solvents of low dielectric constant. In eq 1, which resembles Drago’s expression, except that -AHo has been replaced with log K1, C and E are identified with the tendency of each Lewis acid A or base B to undergo covalent or ionic bonding. This interpretation of the significance of the C and E parameters seems most reasonable in the light of the work of Klopman9 on the origin of hardness and softness in acids and bases. Klopman9 found softness to be associated Rith “frontier-controlled’’ (covalent) and hardness with “charge-controlled’’ (ionic) bonding in calculations based upon polyelectronic pertubation theory. We have therefore adopted the E and C formalism of Drago and co-workers8 in this paper as probably being the best interpretation of the parameters in a four-parameter equation such as (1).
TL;DR: In this article, the major product from 1,1'-bicyclohexenyl in the presence of SnCl4, SbF5, and SbCl5 is the corresponding cyclic sulphone, whereas the cyclic peroxide is almost exclusively formed in this medium with MoCl5, WCl6 and VOCl3.
Abstract: 1,1'-Bicyclohexenyl and α-terpinene are converted into the corresponding cyclic peroxides in the presence of oxygen and Lewis acids in dichloromethane. In liquid sulphur dioxide under oxygen, the . major product from 1,1'-bicyclohexenyl in the presence of SnCl4, SbF5, and SbCl5, is the corresponding cyclic sulphone, whereas the cyclic peroxide is almost exclusively formed in this medium with MoCl5, WCl6 and VOCl3. Under the same conditions, α-terpinene is quantitatively oxygenated in a dark reaction, in the absence of added Lewis acids. In a 1 : 1 dichloromethane-sulphur dioxide medium, ergosteryl acetate requires irradiation for conversion into the corresponding peroxide. Mechanistic interpretations of these observations are presented.
TL;DR: The reaction of antimony (III) halides, SbX3, with Lewis bases has been studied calorimetrically in 1.2-dichloroethane solution as mentioned in this paper.
TL;DR: In this article, reactions in inert solvents between tetrasulphur tetranitride and Lewis acids have given new adducts S 4 N 4 ·A (A = PhBCl 2, TiI 4, HfCl 4, NbF 5, TaF 5, WBr 4 ), S 4 4 ·2A′ (A′ = AlBr 3, GaCl 3, InCl 3, FeCl 3 ) and S 4 n 4 ·4TiF 4.
TL;DR: The addition of an equivalent of Cl 2, Br 2 or I 2 to a solution of Na[H 3 BCN] in glyme (1,2-dimethoxyethane) yields the cyanoborane cyclic oiligomers previously reported as discussed by the authors.
TL;DR: In this article, the system W(CO) 6 /CCl 4 /olefin leads to the olefin metathesis reaction under ultraviolet irradiation (λ 350 nm).
Patent•
ARCO1
TL;DR: In this article, the authors describe a rearrangement of an (alkoxycarbonyl)phenylaminomethylphenyl compound having the general formula "STR1", where x, y and z may also have at least one hydrogen; R is a 1 to 3 carbon alkyl group and Ar is phenyl which may be substituted with a 1-to-3 carbon atom alkonyl group.
Abstract: Diphenylmethane mono and dicarbamates and polymethylene polyphenyl carbamate homologs and derivatives of these compounds are produced by the protonic or Lewis acid catalyzed rearrangement of an (alkoxycarbonyl)phenylaminomethylphenyl compound having the general formula ##STR1## INCLUDING THE HIGHER HOMOLOGS OF SUCH COMPOUNDS, WHEREIN X, Y AND Z, WHICH ARE DIFFERENT ON THE RING, ARE AN ALKYL GROUP HAVING FROM 1 TO 3 CARBON ATOMS, AN --NHCOOR, --CH 2 ArNHCOOR or --N(COOR)CH 2 Ar group; x, y and z may also be at least one hydrogen; R is a 1 to 3 carbon alkyl group and Ar is phenyl which may be substituted with a 1 to 3 carbon atom alkyl group.
Patent•
07 Aug 1978TL;DR: In this paper, a transition metal compound containing at least one π-bonded arene is contacted with an inorganic oxide, hydroxide, oxyhalide, hydroxyhalide or halide.
Abstract: A transition metal compound containing at least one π-bonded arene is contacted with an inorganic oxide, hydroxide, oxyhalide, hydroxyhalide or halide. The transition metal compound can be a compound such as titanium(O)ditoluene or TiCl2.2AlCl3 durene. The inorganic compound is preferably of high surface area and this may be inherent in the compound or can be achieved by a grinding procedure. The inorganic compound can be treated with a halogen containing compound either before, during or after the contacting with the transition metal compound. The product of the contacting is useful either as catalyst for the polymerization of unsaturated hydrocarbon monomers or as a component of such a catalyst. When used as a component of an olefine polymerization catalyst, the transition metal product can be mixed with an organo-aluminum compound and a Lewis Base compound such as an ester. The catalysts can be used to polymerize or copolymerize olefine monomers to obtain a high yield of a polymer having good properties. Some of the catalysts produce polymers of high molecular weight which have an interesting combination of properties.