Search

1,3-dicholoro-1,3-bis(dialkylamino)propenium salts are prepared by condensing N,N,-dialkylamides with dichloromethylene dimethyliminium chloride ("Viehe's salt"). The products are versatile synthons and can be used to make a variety of lig-and types. Here, we report the syntheses of a number of new propenium salts and provide comprehensive characterization data for some that have already been described. Additionally we have prepared a series of related 1,3-dihalo-1,3-bis(dimethylamino)propenium salts via halogen exchange reactions (F through I). Finally all of the compounds described, including Viehe's Salt and several hydrolysis products, have been characterized in the solid state using single crystal X-ray diffraction. The symmetrical cations [[[Me.sub.2]NC(X)CHC(X)N[Me.sub.2]].sup.+] were found to take one of two general structural forms. The first (X = H or F) is planar, presumably maximizing the delocalization within the backbone of the cation, while the second form is markedly twisted (X = Cl, Br or I). Calculations indicate that the latter develop increasingly positive regions of the electrostatic potential on the halide substituents, allowing cation/anion interactions via halogen bonding to dominate in the extended solids. The results of these studies illustrate the importance of the differing interionic interactions in a homologous series of small organic salts. Key words: X-ray crystallography, carbocation, 1,3-bis(dimethylamino)propenium cation, vinamidinium ion, Viehe's salt, Introduction 1,3-Bis(dimethylamino)propenium ions, or vinamidinium ions, have been shown to be powerful synthons for the preparation of [C.sub.3]-backbone ligands, since they are easily functionalized and readily undergo substitution. In the [...]

(Bromoethynyl)benzene dissolved in hexane reacts with l,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) to produce the acetylenic amidinium salt [Ph-C[equivalent to]C-IMes][Br]. Treatment of the bromide salt with [KPF.sub.6] then results in the isolation of solid [Ph-C[equivalent to]C-IMes][[PF.sub.6]]. Both salts have been characterized spectroscopically and their structures determined using X-ray crystallography. Crystals of a hydrolysis product were also isolated from this reaction on one occasion and its structure is reported. This led us to explore the reactivity of the bromide salt further. It was found to react rapidly with sodium azide (Na[N.sub.3]), azidotrimethylsilane ([(C[H.sub.3]).sub.3]Si-[N.sub.3]), cyanotrimethylsilane ([(C[H.sub.3]).sub.3]Si-CN), and also with IMes. All of the addition products have been characterized using X-ray crystallography. Key words: X-ray crystallography, alkyne, N-heterocyclic carbene, C-H bond activation, triazole, Introduction Acetylenic iminium 1 and amidinium 2 (Fig. 1) ions are interesting species since they combine, in one molecule, two reactive and versatile functional groups in close proximity. It was [...]

N-phenyl phenothiazine is one of the most reducing photoredox catalysts. Its synthesis commonly requires transition metal-catalyzed cross-coupling reactions. Here, we show the syntheses of four aryl phenothiazines via a benzyne route, including a multigram-scale synthesis of N-phenyl phenothiazine. While yields are modest, the simplicity, low cost, and lack of requirement for cross-coupling catalysts in this synthesis will be attractive to users of this photocatalyst. Key words: synthesis, N-phenyl phenothiazine, photocatalyst, benzyne, additions La N-phenylphenothiazine est l'un des catalyseurs photoredox qui possedent le plus grand pouvoir reducteur. Sa synthese necessite generalement des reactions de couplage croise catalysees par des metaux de transition. Dans le cadre des presents travaux, nous presentons la synthese de quatre arylphenothiazines par une voie faisant intervenir un intermediaire benzyne, et notamment une synthese de la N-phenylphenothiazine a l'echelle de plusieurs grammes. Bien que les rendements soient modestes, la simplicite, le faible cout et l'absence de recours a des catalyseurs de couplage croise pour realiser cette synthese font de ce photocatalyseur une option interessante pour les utilisateurs. [Traduit par la Redaction] Mots-cles : synthese, N-phenylphenothiazine, photocatalyseur, benzyne, reactions d'addition, Introduction N-aryl phenothiazines have recently emerged as strongly reducing metal-free photoredox catalysts. (1) While highly active precious metal-containing polypyridyl catalysts are commonly used in photoredox catalysis, metal-free catalysts are attractive [...]

The bis(dialkylphosphino)amines R2PNHPR2 react with elemental halogens X2 in dichloromethane to produce cationic products of the general form [(R)2P(X)-N-(R)2P(X)]+ (R = i-Pr, Ph, and t-Bu; X = Cl, Br, and I). All of the nine possible products have been isolated and characterized using X-ray difraction. The dichloro compounds crystallize as [HCl2]- salts, while the dibromo and diiodo products have been isolated as trihalides, [X3]-. A number of these compounds have been shown to react further with methanol to produce salts containing [(R)2P(OC[H.sub.3])N(R)2P(OC[H.sub.3])]+ cations, some of which have also been characterized using X-ray crystallography. The conversion of [(Ph)2P(I)-N-(Ph)2P(I)][I3] to [(Ph)2P(OC[H.sub.3])-N-(Ph)2P(OC[H.sub.3])][I3] was monitored using [.sup.31]P NMR spectroscopy that revealed a stepwise reaction of the former compound with methanol. The results are discussed within the context of coupled reactions; this is then used to rationalize a mechanism for the formation of a rare catenated bismuth compound we reported previously. We suggest that the formation of the weak Bi-Bi bonds is ofset by a coupled or a connected reaction mechanism, involving an irreversible reaction forming strong P-OR bonds in another of the isolated products. Key words: bis(dialkylphosphino)amines, halogenation, coupled reaction, crystal structure, bismuth Les bis(dialkylphosphino)amines R2PNHPR2 reagissent avec les halogenes elementaires X2 dans le dichloromethane pour former des produits cationiques de forme generale [(R)2P(X)-N-(R)2P(X)]+ (R = i-Pr, Ph, t-Bu; X = Cl, Br, I). Les neuf produits possibles ont ete isoles et caracterises par difraction des rayons X. Les composes dichloro cristallisent sous forme de sels [HCl2]-, tandis que les produits dibromo et diiodo ont ete isoles sous forme de trihalogenures [X3]-. Un certain nombre de ces composes subissent une autre reaction avec le methanol pour produire des sels contenant des cations [(R)2P(OC[H.sub.3])N(R)2P(OC[H.sub.3])]+, dont certains ont egalement ete caracterises par radiocristallographie. Nous avons suivi la conversion du [(Ph)2P(I)-N-(Ph)2P(I)][I3] en [(Ph)2P(OC[H.sub.3])-N-(Ph)2P(OC[H.sub.3])][I3] par RMN [.sup.31]P, qui a revele une reaction par etapes du premier compose avec le methanol. Nous discutons des resultats dans le contexte des reactions couplees; que nous utilisons par la suite pour expliquer le mecanisme de formation hypothetique d'un rare compose de bismuth concatene que nous avons publie anterieurement. Nous posons l'hypothese selon laquelle la formation des liaisons Bi-Bi faibles est compensee par un mecanisme de reaction couplee ou connectee, qui comporte une reaction irreversible formant des liaisons P-OR fortes dans un autre des produits isoles. [Traduit par la Redaction.] Mots-cles : bis(dialkylphosphino)amines, halogenation, reaction couplee, structure cristalline, bismuth, Introduction Ambidentate bis(dialkylphosphino)amines 1(H)-3(H) (Fig. 1) are a class of electron-rich phosphorus ligands with a P-N-P backbone. (1,2) These compounds, here abbreviated by PNP, have been used in a variety [...]

N-Heterocyclic carbenes [1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene 1a (IMes) or 1,3-bis(2,6-di-iso-propylphenyl)imidazolidene 1b (SIPr)] react with the polarized alkenes 2 and 4 to form the crystalline betaines 3a, 3b, and 5a. Furthermore, a one-pot reaction between an aldehyde, malononitrile, and an imidazolium salt of an N-heterocyclic carbene has been developed for the efficient preparation of betaine 5a without isolation of the free carbene. Full characterization data, including X-ray crystal structures, is reported for the three synthesized betaines. The structures of the betaines 3a, 3b, and 5a shed new light on the initial products formed in the reactions between N-heterocyclic carbenes and compounds containing polarized double bonds. Key words: N-heterocyclic carbenes, polarized alkenes, betaines, Breslow intermediate. Les carbènes N-hétérocycliques [1,3-bis(2,4,6-triméthylphényl)imidazol-2-ylidène 1a (IMes) ou 1,3-bis(2,6-diisopropyl)phényl-4,5-dihydro-imidazol-2-ylidène 1b (SIPr)] réagissent avec les alcènes polarisés 2 et 4 pour former les bétaïnes cristallines 3a, 3b et 5a. De plus, nous avons mis au point une réaction monotope entre un aldéhyde, le malononitrile et le sel d'imidazolium d'un carbène N-hétérocyclique permettant de préparer efficacement la betaine 5a sans isoler le carbène libre. Nous présentons les données complètes de caractérisation, dont les structures cristallines observées par diffraction des rayons X, pour les trois bétaïnes que nous avons synthétisées. Les structures des bétaïnes 3a, 3b et 5a ont permis de jeter un regard nouveau sur les produits initiaux formés lors des réactions entre les carbènes N-hétérocycliques et les composés contenant des doubles liaisons polarisées. [Traduit par la Rédaction] Mots-clés : carbènes N-hétérocycliques, alcènes polarizes, bétaïnes, intermédiaire de Breslow., Introduction Zwitterions are amphiphilic neutral compounds with asymmetric charge distributions. They are useful in regulating physical properties of molecules, including solubility and aggregation control, and thus find broad application in [...]

Sulfenyl dipyrroles feature two pyrroles linked via a sulfenyl bridge. The synthesis of sulfenyl dipyrroles has typically involved [SCl.sub.2] as the sulfur source. However, [SCl.sub.2] is no longer readily available within North America and Europe. Herein we report a new synthesis of sulfenyl dipyrroles using [SOCl.sub.2] as the sulfur source and reductant. Although five new sulfenyl dipyrroles were synthesized and isolated via this route, functional group tolerance proved limited. A potential mechanism for the reaction, involving reduction of a sulfinyl moiety by [SOCl.sub.2], is briefly explored. Key words: sulfur, pyrrole, organic synthesis, in-situ reduction of sulfinyl dipyrroles. Les sulfenyldipyrroles sont constituees de deux pyrroles relies par un pont sulfenyle. Dans la synthese des sulfenyldipyrroles, le [SCl.sub.2] est habituellement employe comme source de soufre. Or, le [SCl.sub.2] n'est plus facilement accessible en Amerique du Nord et en Europe. Dans cet article, nous presentons une nouvelle synthese des sulfenyldipyrroles qui fait intervenir le [SOCl.sub.2] comme source de soufre et comme agent reducteur. Bien que nous soyons parvenus a synthetiser et a isoler cinq nouveaux sulfenyldipyrroles par cette methode, la tolerance des groupes fonctionnels s'est revelee limitee. Nous avons explore un mecanisme de reaction possible, qui impliquerait la reduction d'une fraction sulfinyle par le [SOCl.sub.2]. [Traduit par la Redaction] Mots-cles : soufre, pyrrole, synthese organique, reduction in situ des sulfinyldipyrroles., Introduction The sulfenyl dipyrrolic motif, featuring two pyrroles linked via a sulfenyl bridge (1, V = S, Fig.1), has been known since the 1930s. (1) The most common application of [...]

A series of mono- and bis-ethynyl phosphonium salts have been prepared via reaction of bromoacetylenes, Ph-C[equivalent to]C-Br or Br-C[equivalent to]C-[C.sup.6][H.sup.4]-C[equivalent to]C-Br, with various phosphines. Some of the derivatives reported are previously known, ([Ph-C[equivalent to]C-P[Ph.sub.3]]Br, [Ph-C[equivalent to]C-P[Me.sub.3]]Br, [Ph-C[equivalent to]C-P[Bu.sub.3]]Br, and [[Ph.sub.3]P-C[equivalent to]C-[C.sub.6][H.sub.4]-C[equivalent to]C-P[Ph.sub.3]][[Br.sub.2]]), however typically these are missing complete spectroscopic characterization and many have been prepared using much more complicated methods. The derivative [Ph-C[equivalent to]C-PP[Ph.sub.3]]Br is capable of inhibiting the growth of tumour cells and has been shown crystallographically to have a significant interaction with the heat shock proteins (HSP70 or DnaK). Thus, solid state structures for all seven phosphonium salts prepared have been reported as they may be of interest to others in this field. Sterically encumbered phosphines such as [Mes.sub.3]P did not react with Ph-C[equivalent to]C-Br; however, [(2,4,6-MeO-[C.sub.6][H.sub.2]).sub.3]P was found to slowly react at moderate temperature to give the expected alkynyl phosphonium salt. However, at higher temperatures, the alkynyl phosphonium undergoes an intramolecular cyclization to form a phosphonium analogue of a 1,4-oxazine. Finally, electronic structure calculations reveal the positive charge on the acetylenic [beta]-carbon, a result of a significant contribution of other canonical structures. The flexibility of the P-C[equivalent to]C bond has been investigated showing a low-energy barrier ( Key words: main group chemistry, phosphorus, phosphonium, X-ray crystallography. Nous avons prepare une serie de sels de mono-ethynylphosphonium et de bis-ethynylphosphonium en faisant reagir les bromoacetylenes Ph-C[equivalent to]C-Br ou Br-C[equivalent to]C-[C.sub.6][H.sub.4]-C[equivalent to]C-Br avec diverses phosphines. Certains des derives que nous presentons sont deja connus : ([Ph-C[equivalent to]C-P[Ph.sub.3]]Br, [Ph-C[equivalent to]C-P[Me.sub.3]]Br, [Ph-C[equivalent to]C-P[Bu.sub.3]]Br et [[Ph.sub.3]P-C[equivalent to]C-[C.sub.6][H.sub.4]-C[equivalent to]C-P[Ph.sub.3]][[Br.sub.2]]). Cependant, la plupart de ces derniers n'avaient pas fait l'objet d'une caracterisation spectroscopique complete et bon nombre d'entre eux avaient ete synthetises par des methodes beaucoup plus compliquees. Le derive [Ph-C[equivalent to]C-P[Ph.sub.3]]Br s'est revele capable d'inhiber la croissance des cellules tumorales et a montre par cristallographie une interaction importante avec les proteines de choc thermique (Hsp70 ou DnaK). Par consequent, nous avons publie les structures a l'etat solide des sept sels de phosphonium que nous avons prepares, car ces derniers pourraient presenter un interet pour d'autres chercheurs dans ce domaine. Les phosphines steriquement encombrees comme la [Mes.sub.3]P n'ont pas reagi avec le Ph-C[equivalent to]C-Br, quoique la [(2,4,6-MeO-[C.sub.6][H.sub.2]).sub.3]P a reagi lentement a ttemperaturemodereepourproduireseld'alcynylphosphoniumattendu.Cependant,:adestemperaturespluselevees,l'alcynylphos-phonium subit une cyclisation intramoleculaire pour former un analogue phosphonium de la 1,4-oxazine. Enfin, les calculs de structure electronique revelent que le carbone [beta] acetylenique est charge positivement; ce qui temoigne d'une contribution importante des autres structures canoniques. Nous avons etudie la flexibilite de la liaison P-C[equivalent to]C et nous avons observe que la barriere d'energie de flexion etait faible ( Mots-cles : chimie des elements du groupe principal, phosphore, phosphonium, radiocristallographie., Introduction Since their initial discovery, (1) ethynylphosphonium salts continue to be popular and extremely valuable building blocks in organic synthesis. These compounds have classically been used as electrophiles, allowing for [...]

Eight lipophilic 3-hydroxy-4-pyridinones have been prepared from a microwave-mediated reaction along with the corresponding copper(II) complexes. All complexes have been obtained elementally pure and X-ray diffraction studies on two of the copper complexes have confirmed the structure of these compounds. Some of these complexes showed a promising degree of anti-mycobacterial activity against Mycobacterium tuberculosis, where activity seemed to vary by substitution at the pyridinone nitrogen atom. Key words: aliphatic amines, anti-mycobacterial, copper, hydroxypyridinones, lipophilic, tuberculosis. Huit 3-hydroxy-4-pyridinones lipophiles et leurs complexes du cuivre(II) correspondants ont ete synthetises lors d'une reaction provoquee par des micro-ondes. Tous les complexes ont ete obtenus sous leur forme pure et des analyses diffractometriques aux rayons X des deux complexes du cuivre ont confirme la structure de ces composes. Certains de ces complexes ont presente un niveau prometteur d'activite antimycobacterienne contre Mycobacterium tuberculosis, cette activite semblant varier par substitution au niveau de l'atome d'azote de la pyridinone. [Traduit par la Redaction] Mots-cles: amines aliphatiques, antimycobacterien, cuivre, hydroxypyridinones, lipophile, tuberculose., Introduction All but forgotten in some societies, tuberculosis remains a serious infectious disease and is the leading cause of death in most of the developing countries around the world. Indeed, [...]

The bis(tert-butylimido)-molybdenum(VI) framework has previously been used for the successful atomic layer deposition (ALD) and chemical vapor deposition of many molybdenum-containing thin films. Here, we have prepared and fully characterized a new thermally robust bis(tert-butylimido)molybdenum(VI) complex, bis(tert-butylimido)-bis(N-2-(tert-butyliminomethyl)pyrrolato)-molybdenum(VI), (tBuN)2Mo(PyrIm)2 (1), that incorporates two N,N'-κ2-monoanionic ligands. The volatility and thermal stability of 1 were measured using thermogravimetric analysis and differential scanning calorimetry, where it was found to achieve a vapor pressure of 1 Torr at 212 °C and had an onset of thermal decomposition at 273 °C. A comparison of its thermal properties with those of the known ALD precursor (tBuN)2Mo(dpamd)2 (dpamd = N,N'-diisopropyl-acetamidinato) showed that 1 had similar volatility but a 78 °C improvement in thermal stability. Preliminary deposition experiments indicated that 1 should be a good ALD precursor; it exhibited self-limiting adsorption and did not decompose on the surface until at least 500 °C, features that will enable its use in the development of new high-temperature ALD processes. [ABSTRACT FROM AUTHOR]

The bis(dialkylphosphino)amines R2PNHPR2 react with elemental halogens X2 in dichloromethane to produce cationic products of the general form [(R)2P(X)-N-(R)2P(X)]+ (R = i-Pr, Ph, and t-Bu; X = Cl, Br, and I). All of the nine possible products have been isolated and characterized using X-ray diffraction. The dichloro compounds crystallize as [HCl2]− salts, while the dibromo and diiodo products have been isolated as trihalides, [X3]−. A number of these compounds have been shown to react further with methanol to produce salts containing [(R)2P(OCH3)N(R)2P(OCH3)]+ cations, some of which have also been characterized using X-ray crystallography. The conversion of [(Ph)2P(I)-N-(Ph)2P(I)][I3] to [(Ph)2P(OCH3)-N-(Ph)2P(OCH3)][I3] was monitored using 31P NMR spectroscopy that revealed a stepwise reaction of the former compound with methanol. The results are discussed within the context of coupled reactions; this is then used to rationalize a mechanism for the formation of a rare catenated bismuth compound we reported previously. We suggest that the formation of the weak Bi–Bi bonds is offset by a coupled or a connected reaction mechanism, involving an irreversible reaction forming strong P–OR bonds in another of the isolated products. [ABSTRACT FROM AUTHOR]

X-ray crystallographic studies of two axial glycosyl sulfoxides having [R.sub.S] configurations (derivatives of phenyl 2-azido-2-deoxy-1-thio-α-D-galactopyranoside S-oxide) show that they adopt anti conformations in the solid state, in contrast to previous observations and assumptions. Density functional theory (DFT) calculations at the B3lYP6-311G+(d,p)/ 6-31G(d) level confirm that anti conformations of both phenyl and methyl [R.sub.S] glycosyl sulfoxides of 2-azido-2-deoxy-α-D-pyranosides are more stable than exo-anomeric conformations in the gas phase. 1D NOE measurements indicate that the more polar exo-anomeric conformers are only populated to a slight extent in solution. The anti conformations are distorted so that the glycosyl substituents are closer to being eclipsed with H1. This distortion allows S n → [σ.sup.*] overlap if the sulfur lone pair is a p-type lone pair. Evidence for this overlap comes from short C1-S bond distances, as short as the comparable bond distances in the X-ray crystal structure and in the results from DFT calculations for the [S.sub.S] glycoside, which does adopt the expected exo-anomeric conformation, both in the solid state and in solution, and has normal n → [σ.sup.*] overlap. For 2-deoxy derivatives not bearing a 2-azido group, gas-phase DFT calculations at the same level indicate that the anti- and exo-anomeric conformers have comparable stabilities. Comparison of the results of the two series shows that electronegative substituents in equatorial orientations at C2 destabilize conformations with parallel S-O arrangements, the conformation favored by having an endocyclic C-O dipole antiparallel to the S-O dipole, by about 2.5 kcal [mol.sup.-1] (1 cal = 4.184 J). An equatorial glycosyl sulfoxide, ([S.sub.S]) phenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-1-thio-β- D-glucopyranoside S-oxide, also adopts an anti conformation in the solid state as shown by X-ray diffraction. It also adopts this conformation in solution, in contrast to studies of other equatorial glycosyl sulfoxides. Key words: sulfoxide configurations, glycosyl sulfoxides, conformational analysis, density functional theory (DFT) calculations, 1D NOE measurements, X-ray crystallography. Des etudes de cristallographie par diffraction des rayons-X de deux glycosyles sulfoxydes axiaux de configurations [R.sub.S], des derives du S-oxyde de 2-azido-2-desoxy-1-thio-a-galactopyranoside de phenyle, montrent qu'ils adoptent des conformations anti a l'etat solide, contrairement aux observations anterieures et aux hypotheses. Des calculs selon la theorie de la fonctionnelle de la densite; (TFD) au niveau B31YP6-311G+(d,p)/6-31G(d) confirment que les conformations anti que, en phase gazeuse, chacun des [R.sub.S] glycosyles sulfoxydes, 2-azido-2-desoxy-1-thio-α- galactopyranoside tant de methyle que de phenyle sont plus stable dans les conformations anomeres exo. Des mesures d'effet Overhauser nucleaire (eOn) 1D indiquent que, en solution, les conformeres anomeres les plus polaires ne forment qu'une faible partie de la population. Les conformations anti sont deformees de facon a ce que les substituants glycolyses soient dans une position pratiquement eclipsee avec le H1. Cette distorsion permet un recouvrement S n → [σ.sup.*] sur la paire libre du soufre est une paire libre de type p. Un support pour ce recouvrement vient des courtes longueurs de liaison C1-S, pratiquement aussi courtes que les longueurs mesurees par diffraction des rayons-X dans la structure cristalline et en accord avec les resultats des calculs TFD pour le [S.sub.S] glycoside qui adopte la conformation anomere exo attendue, tant a l'etat solide qu'en solution, et pour le recouvrement n → [σ.sup.*] normal. Pour les derives 2-desoxy ne portant pas de groupe azido, les calculs de TFD en phase gazeuse, au meme niveau, indiquent que les conformeres anomeres anti et exo ont des stabilites comparables. Une comparaison des resultats des deux series montre que les substituants electronegatifs en orientations equatoriales en C2 destabilisent les conformations avec des arrangements S-O paralleles, la conformation favorisee par un dipole C-O endocyclique antiparallele au dipole S-O par environ 2,5 kcal [mol.sup.-1] (1 cal = 4.184 J). La diffraction des rayons-X montre aussi que, a l'etat solide, un glycosyle sulfoxyde equatorial, le S-oxyde du [S.sub.S] 3,4,6-tri-O-acetyl-2-desoxy-2- phtalimido-1-thio-β-D-glucopyranoside de phenyle, adopte aussi une conformation anti. Il adopte aussi cette conformation en solution, en opposition a ce qui a ete observe dans les etudes sur glycosyles sulfoxydes equatoriaux. Mots-cles: configurations de sulfoxydes, glycosyles sulfoxydes, analyse conformationnelle, calculs selon la theorie de la fonctionnelle de la densite (TFD), mesures d'effet Overhauser nucleaire (eOn) 1D, cristallographie., Introduction One of the most important techniques for the formation of glycosides employs glycosyl sulfoxides activated by electrophiles as leaving groups. (1) This method has been used to form glycosides [...]

Abstract: The synthesis of an 'unknown' Fe(II) complex originally reported in 1973 and formulated then as [Fe(DMSO)5C1] [Sn[Cl.sub.4]] was thoroughly reproduced and the compound reformulated as the novel [Fe[(DMSO).sub.6]] [Sn[Cl.sub.6]] [...]

The inter/intramolecular interactions (S...I, S...S, I...I, and I...H) present in the iodoform octasulfur molecule are investigated based on the properties of the electron density at the bond critical point (BCP). The results have shown that these interactions play an important role in the stability of the crystalline state of iodoform octasulfur.

Abstract: The tetraiphenylphosphonium squarate salt crystallizes with a number of diverse interactions, which all have the potential to be classified as hydrogen bonds. The squarate anions are found as dimers [...]

We report the synthesis, using an organic-template-free hydrothermal crystallization method, and catalysis of a new type of nanocomposite material, 1.3 nm-sized Ru[O.sub.2] particles confined in faujasite zeolite. The zeolite-confined Ru[O.sub.2] composites were fully characterized with X-ray powder diffraction, Ru K-edge X-ray absorption, and high-resolution transmission electron microscopy. XRD and X-ray fluorescence analysis indicate that the framework is faujasite zeolite with a Si:A1 ratio of 1.25. Ru K-edge X-ray absorption near-edge structures indicate that the ruthenium species in the zeolite is Ru(IV) with nearest-neighbor octahedral environments similar to hydrous Ru[O.sub.2], i.e., distorted "Ru[O.sub.6]". The [k.sup.2]-weighted extended X-ray absorption fine structure indicates that the Ru(IV) species anchored in the zeolite likely form amorphous Ru[O.sub.2] with a 2D-chain structure, in which Ru[O.sub.6] units are connected together by two shared oxygen atoms. TEM shows that the particle size of Ru[O.sub.2] encapsulated inside the supercages of FAU is about 1.3 nm. The Ru[O.sub.2]-FAU composites display significant catalytic activity in the oxidation of cyclohexane with BHP under mild (room temperature and 1 atm (1 atm [equivalent]101.325 kPa)) conditions. The ketone and alcohol concentration can be as high as 0.26 mol [L.sup.-1] in 5 h with 48% peroxide efficiency. The catalyst is stable and reusable. Possible oxidation mechanisms are also discussed. Key words: nanocomposite, ruthenium oxide, catalysis, oxidation, zeolite.

The crystal structures of the tetraphenylborates of the dabco[H.sup.+], guanidinium (MeCN solvate), and biguanidiniun cations are shown to contain a variety of C-H ... H-C dihydrogen (DB) bonds of nominally zero polarity, as well as a variety of N-H ... N, C-H ... N, N-H ... Ph, and C-H ... Ph hydrogen (HB) bonds. These intermolecular bonds have been characterized topologically after multipole refinement of the structures. The coexistence of the DBs and HBs in each of the structures makes it possible to establish their relative strength hierarchy. It also illustrates the importance of the DBs in satisfying the tendency of these structures to maximize the total intermolecular bonding engagement. To compare the above DBs with other DBs, the results of an extensive set of MP2/6-31G(d,p) calculations (supplied by I. Alkorta) were analyzed for reference correlations between the bond-critical parameters. Thus, for an X-H ... H-Y bond, the difference [Delta][epsilon][(H).sub.m] between the Mulliken charges on the H atoms in the uncomplexed X-H and H-Y components correlates quite well with the X-H ... H-Y parameters and can be used for predicting the topological strength of an X-H ... H-Y bond. The use of the difference [Delta][epsilon][(H).sub.c] in the bond does not appear to change the correlation significantly; closer correlations are observed when the amount of charge transferred on formation of the H ... H bond is used instead of [Delta][epsilon][(H).sub.m] or [Delta][epsilon][(H).sub.c]. Bonding interactions are obtained even between like or symmetry-related H atoms as a consequence of induced-dipole interactions, which accounts for the existence of the above intermolecular C-H ... H-C bonds with d(H ... H) = 2.18-2.57 [Angstrom] electron density at the bond-critical point of [Tilde]0.05-0.08 e/[Angstrom .sup.3], and a rough estimate of the H ... H binding energy of [Tilde]1-5 kcal/mol. Examination of the bond-critical parameters of X-H ... H-Y bonds also suggests a criterion of stability of these bonds with respect to the transition from non-shared (closed-shell) X-H ... H-Y interaction to covalent (shared-shell) X ... H-H ... Y interaction. This transition appears to be discontinuous. Key words: bond-critical parameters, bond topology, dihydrogen bonds, hydrogen bonds, organoammonium tetraphenylborates.

As part of a systematic development of bismuth coordination chemistry, we are exploiting the thermodynamic and hydrolytic stability of Bi--S bonds. A series of heteroleptic thiolate bismuth complexes have been isolated and characterized. The generally applicable synthetic methodology involves the use of hetero-bifunctional ligands containing a thiolate moiety as an anchor to facilitate coordinate interaction of weak donors (carbonyls, amines, hydroxyls) with bismuth. The bifunctional nature of the ligands is manifested in chelating roles. Important comparisons with established thiolate complexes of bismuth are discussed. Key words: bismuth, thiolate, heteroleptic, crystallography.

Methods were developed to convert dipentaerythritol efficiently into di-[OMICRON]-benzylidene, di-[OMICRON]-cyclohexylidene, di-[OMICRON]-l-ethylpropylidene, and di-[OMICRON]-methylene diacetals. The known di-[OMICRON]-benzylidene acetal, considered to be a single isomer, was shown to be close to a statistical mixture of the cis, cis-,cis,trans-, and trans,trans-isomers. Structures were established by a combination of NMR spectroscopy and X-ray crystallography. Reaction of the di-[OMICRON]-benzylidene acetals with benzyl chloride and potassium hydroxide surprisingly gave good to excellent yields of the monobenzyl ethers. An explanation for this observation was advanced. The dibenzyl derivatives of the di-[OMICRON]-benzylidene acetals were formed by reaction of their dianions with benzyl bromide in DMF. Selective reduction of the di-[OMICRON]-benzylidene acetals with triethylsilane and boron trifluoride etherate gave 2',6'-di-[OMICRON]-benzyldipentaerythritol. A crown ether was formed in modest yield (12%) by reaction of the dianion of the di-[OMICRON]-methylene acetal with [alpha],[alpha]'-dibromo-m-xylene in DMF. Key words: dipentaerythritol, pentaerythritol, acetals, dendrimer, selective benzylation, crown ether.

Research has been conducted on the nucleophilic carbene. The reactions of this compound with diazofluorene, diphenyldiazomethane and azidotrimethylsilane have been investigated via single-crystal X-ray crystallography and the results are discussed.

The effectiveness of simple sulfinyl and sulfonyl groups as electron-withdrawing protecting groups for pyrroles is analyzed using (super 13)C NMR spectroscopy and confirmed by consideration of X-ray crystal structures. The 2,4-dinitrobenzenesulfinyl and sulfonyl groups are shown to be effective electron-withdrawing protecting groups for pyrroles.

The title compound, [Co(C10H15)(C2H4)2], was prepared by Na/Hg reduction of [Co2(C10H15)2(μ-Cl)2] in THF under an ethylene atmosphere and crystallized from pentane at 193 K. The Co-C(olefin) bonds have an average length of 2.022 (2) Å, while the Co-C(pentadienyl) bonds average 2.103 (19) Å. The olefin C C bonds are 1.410 (1) Å. The dihedral angle between the planes defined by the cyclopentadienyl ligand and the two olefin ligands is 0.25 (12)°. In the crystal, molecules are linked into chains by C-H...πinteractions. [ABSTRACT FROM AUTHOR]

The synthesis of an "unknown" Fe(II) complex originally reported in 1973 and formulated then as [Fe(DMSO)5Cl][SnCl4] was thoroughly reproduced and the compound reformulated as the novel [Fe(DMSO)6][SnCl6] double complex salt. Current elemental analysis and IR and Mössbauer spectroscopy matched the original 1973 data, and Raman spectroscopy and single crystal X-ray diffraction provided additional confirmation of our reformulation. [Fe(DMSO)6][SnCl6] (1) crystallizes in the trigonal space group R[IMG] with octahedral [Fe(DMSO)6]2+ and [SnCl6]2– complex ions with an Fe—O bond length of 2.121(3) Å. The same synthesis was extended to Co(II) and Ni(II) to generate the novel [Co(DMSO)6][SnCl6] (2), which crystallizes in the triclinic space group P[IMG] with a Co—O bond length of 2.093(4)–2.113(5) Å, and [Ni(DMSO)6][SnCl6] (3), which crystallized in the trigonal R[IMG] space group and has a Ni—O bond length of 2.062(2) Å. The Sn—Cl bond length in all three complexes ranged from 2.421(2) to 2.448(2) Å.Key words: DMSO complexes of Fe(II), Co(II) and Ni(II), SnCl62– salts, IR, Raman and Mössbauer spectroscopy, X-ray crystal structures. La synthèse d'un complexe "inconnu" de Fe(II), qui avait originalement été rapportée en 1973 et pour lequel la formule [Fe(DMSO)5Cl][SnCl4] avait alors été proposée, a été complètement reproduite et on peut maintenant lui attribuer la formule [Fe(DMSO)6][SnCl6], un double sel complexe. Les données obtenues au cours de ce travail pour les analyses élémentaires, les spectres infrarouge et de Mössbauer correspondent à celles qui avaient été obtenues dans le travail original de 1973; on a par ailleurs déterminé le spectre Raman et la structure cristalline par diffraction des rayons X sur un cristal unique et ces données ont permis de confirmer notre reformulation. Le complexe [Fe(DMSO)6][SnCl6] (1) cristallise dans le groupe d'espace trigonal R[IMG] avec un ion octaédrique [Fe(DMSO)6]2+ et des ions complexes [SnCl6]2–; la longueur de la distance Fe—O est de 2,121(3) Å. On a étendu cette synthèse au Co(II) et au Ni(II) pour générer la formation du complexe [Co(DMSO)6][SnCl6] (2) qui cristallise dans le groupe d'espace triclinique P[IMG] avec une longueur de la liaison Co—O de 2,093(4)–2,113(5) Å et du complexe [Ni(DMSO)6][SnCl6] (3) qui cristallise dans le groupe d'espace trigonal R[IMG] avec une longueur de la liaison Ni—O de 2,062(2) Å. La longueur de la liaison Sn—Cl dans les trois complexes est de 2,421(2)-2,448(2) Å.Mots-clés : complexes du Fe(II), du Co(II) et du Ni(II) avec le DMSO, sels complexes du SnCl62–, spectroscopie Raman et de Mössbauer, structures cristallines par diffraction des rayons X.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]