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A phosphaguanidine [[Me.sub.2]NC([PPh.sub.2])=[N.sup.i]Pr], the analogous guanidine [[Me.sub.2]NC([NPh.sub.2])=NiPr], and their hydrochloride (HCl) salts were prepared to study the influence of substituting a phosphorus atom for a nitrogen atom on the basicity of the two compounds and the bonding in their conjugate acids. The [pK.sub.a] values of both HCl salts were measured in acetonitrile by NMR titration. Surprisingly, the substitution of P for N has essentially no effect on basicity even though the geometry at that atom is changed. The presence of phenyl substituents in the protonated guanidine reduces the resonance in the [CN.sub.3] core, whereas poor orbital overlap between P and C reduces the resonance in the [N.sub.2]CP core of the protonated phosphaguanidine. The neutral phosphaguanidine binds to a Cu(I) halide through both the [N.sub.imine] and the P, which suggested that the basic N atom on the bound ligand may have little utility as a Bronsted base. Fortunately, however, a Cu(I) halide complex of the protonated phosphaguanidine is stable. Thus, the tendency of the basic N to bind to metals does not proscribe it serving as a metal-proximate Bronsted base. Key words: superbase, basicity, guanidine, coordination chemistry, resonance stabilization. Nous avons prepare une phosphaguanidine [[Me.sub.2]NC([PPh.sub.2])=[N.sup.i]Pr], la guanidine analogue [[Me.sub.2]NC([NPh.sub.2])=[N.sup.i]Pr] et leur sel de chlorhydrate (HCl) afin d'etudier l'influence de la substitution d'un atome d'azote par un atome de phosphore sur la basicite des deux composes ainsi que les liaisons que forme leur acide conjugue. Nous avons mesure les valeurs de [pK.sub.a] des deux sels de chlorhydrate dans l'acetonitrile au moyen d'experiences de titrage par RMN. Etonnamment, la substitution de l'atome de N par un atome de P n'a pratiquement eu aucun effet sur la basicite, meme si la geometrie de l'atome etait modifiee. La presence de substituants phenyle sur la guanidine protonee diminue la resonance dans le noyau [CN.sub.3], tandis que le faible chevauchement entre les orbitales des atomes de P et de C diminue la resonance dans le noyau [N.sub.2]CP de la phosphaguanidine protonee. La phosphaguanidine neutre se lie a un halogenure de Cu(I) par l'intermediaire de l'atome de [Nim.sub.in]e et de l'atome de P, ce qui permet de penser que l'atome de N basique sur le ligand lie ne joue peut-etre pas un role tres important comme base de Bronsted. Heureusement, un halogenure de Cu(I) forme avec la phosphaguanidine protonee un complexe stable. La tendance de l'atome de N basique a se lier aux metaux n'interdit donc pas que ce dernier puisse agir comme base de Bronsted a proximite d'un metal. [Traduit par la Redaction] Mots-cles: superbase, basicite, guanidine, chimie de coordination, stabilisation par resonance., Introduction Guanidines [[([R.sub.2]N).sub.2]C=NR] are organosuperbases that share a Y-shaped '[CN.sub.3]' functional group (Scheme 1, left). Their basicity and nucleophilicity make them useful in many organic syntheses (1,2) and for the [...]

We report the synthesis and solid-state [.sup.17]O NMR characterization of three [.sup.17]O-labeled oxiranes: (2S*,3S*)-2,3-bis(4-nitrophenyl)-[[.sup.17]O]oxirane, (2S*,3R*)-2,3-bis(4-nitrophenyl)-[[.sup.17]O]oxirane, and 2,2,3-triphenyl-[[.sup.17]O]oxirane. In addition, we have determined the crystal structure of (2S*,3R*)-2,3-bis(4-nitrophenyl)oxirane by X-ray crystallography. When the experimentally determined [.sup.17]O NMR tensors for oxiranes (where the C-O-C bond angle is about 60[degrees]) are compared with those for dimethyl ether (where the C-O-C bond angle is 113[degrees]) and other R-O-R' functional groups, we found that the highly constrained geometry of oxiranes results in distinct tensor orientations in the molecular frame of reference. The experimental results are complemented by quantum chemical computations. This study represents the first time that [.sup.17]O chemical shift and quadrupole coupling tensors are simultaneously determined for oxirane compounds. Key words: oxirane, solid-state [.sup.17]O NMR, quadrupole coupling tensor, chemical shift tensor. Nous présentons la synthèse et la caractérisation par RMN[.sup.17]O à l'état solide de trois oxiranes marqués à l'oxygène 17 : le (2S*,3S*)-2,3-bis(4-nitrophényl)-[[.sup.17]O]oxirane, le (2S*,3R*)-2,3-bis(4-nitrophényl)-[[.sup.17]O]oxirane et le 2,2,3-triphényl-[[.sup.17]O]oxirane. En outre, nous avons déterminé la structure cristalline du (2S*,3R*)-2,3-bis(4-nitrophényl)oxirane par radiocristallographie. Lorsque nous avons comparé les valeurs expérimentales des tenseurs en RMN [.sup.17]O des oxiranes (dans lesquels l'angle de la liaison C-O-C est d'environ 60[degrees]) avec ceux du diméthyléther (dans lequel l'angle de liaison C-O-C est de 113[degrees]) et d'autres groupes fonctionnels de type R-O-R', nous avons observé que la géométrie fortement contrainte des oxiranes donne lieu à des orientations différentes des tenseurs dans le cadre de référence moléculaire. Nous présentons des calculs de chimie quantique en complément à nos résultats expérimentaux. Cette étude est la première à décrire la détermination simultanée des tenseurs de déplacement chimique et des tenseurs de couplage quadripolaire de l'oxygène 17 dans des oxiranes. [Traduit par la Rédaction] Mots-clés : oxirane, RMN [.sup.17]O à l'état solide, tenseur de couplage quadripolaire, tenseur de déplacement chimique., Introduction Oxiranes (also known as 1,2-epoxides) are a class of organic compounds containing a three-membered heterocyclic ring of two carbon atoms and one oxygen atom. Oxiranes are important building blocks [...]

A new solid-state inorganic compound, indium dilead pentachloride, InPb2Cl5, was synthesized by melting InCl and PbCl2 in a vacuum-sealed quartz ampoule. The ampoule was heated to 793 K and then slowly cooled to room temperature to induce crystallization of InPb2Cl5. InPb2Cl5 crystallizes in the monoclinic crystal system adopting a space group of type P21/c, which is isostructural with other metal halides such as RbPb2Cl5, KPb2Cl5 and TlPb2Cl5. The bulk InPb2Cl5 exhibits a metallic black/grey colour, allowing it to be separated from white/ yellow Pb2Cl5 crystals. Due to the incongruent nature of the compound, the pure bulk InPb2Cl5 was not obtained. The black/grey InPb2Cl5 crystals were characterized by powder and single-crystal X-ray diffraction. InPbCl3 was also explored, however the growth was unsuccessful. [ABSTRACT FROM AUTHOR]

Abstract: The bulky m-terphenyl phenol Ar*OH 1 (Ar* = [C.sub.6][H.sub.3]-2,6-[Mes.sub.2], Mes = 2,4,6-trimethylphenyl) was synthesized via the treatment of Ar*Li with nitrobenzene. The phenol 1 is prepared in modest to [...]

A study was conducted to determine the effects of varying the [sigma]-electron donor ability of pyridine Lewis-base ligands on the coordination environment of lead(II) in bis-thiolate complexes. The results indicate that lead-nitrogen bond distances is reduced when [sigma]-electron donor ability of the 4-substituted pyridine ligand is increased.

The cystamine conjugate [[(BocNH)Fc(CO)CSA].sub.2] was prepared by coupling cystamine with the N-protected ferrocene amino acid derivative BocHN-Fc-COOH and was fully characterized by spectroscopic methods and by single-crystal X-ray diffraction. The cystamine conjugate forms films on gold substrates, which upon deprotection of the amino group, react with chemical warfare agent (CWA) mimics, upon which the redox properties of the Fc group are affected significantly. Cyclic voltammetry shows 50(5) mV anodic shifts of the Fc redox potentials after exposure to EtSC[H.sub.2]C[H.sub.2]Cl, a simulant for sulfur mustard HD (MA), and (NC)[(EtO).sub.2]P(O), a simulant for nerve agent Tabun (NA). Exposure to MA and NA causes an increase in 2.3 and 4.5 ng mass, respectively, in QCM which indicates ca. 70% efficiency in Boc-deprotection. Ellipsometry measured a film thickness increase from 6([+ or -]1) [Angstrom] for the deprotected film to 10([+ or -]4) [Angstrom] for the film modified with MA and to 7([+ or -]2) [Angstrom] for the film modified with NA. AFM measurements show changes in the thickness and morphology of the film after reaction with MA and NA. The surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and clearly show the attachment of the cystamine conjugate on the surface and its reaction with CWA mimics.

The first magnesium and zinc boraamidinate (bam) complexes are synthesized via metathetical reactions between dilithio atoms and Grignard reagents or MCl2 (M=Mg, Zn). The results show that the bam anionic radical [PhB(N(super t)Bu)(sub 2)](super .-) can be stabilized by coordination to a variety of early main-group metal centers to provide neutral radicals whose relative stabilities are compared and discussed.

Quantitive yields of [((super t)BuNH)Te(mu-N(super t)Bu)2Te(N(super t)Bu)][OSO2CF3] is obtained by the treatment of [((super t)BuNH)Te(mu-N(super t)Bu)2Te(N(super t)Bu)] with HCF3SO3. The study reports about the crystal structures of the partially hydrolyzed products such as [((super t)BuIN)Te(mu-N(super t)Bu)2Te(mu-O)]2(I3)2, [((super t)BuMeN)Te(mu-N(super t)Bu)2Te(mu-O)]2(I3)2, and [((super t)BuMeN)Te(mu-N(super t)Bu)2Te(mu-O)]2(I3)2.2MeCN.

The ability of MP2, B3PW91 and PBE0 methods to produce reliable predictions in structural and spectroscopic properties of small selenium-halogen molecules and cations are demonstrated by using 6-311G(d) and cc-pVTZ basis sets. The experimental FT-Raman spectra of (Sel3)[AsF6] in the solid state and in SO2(I) are also reported.

The reactions of Cd[Cl.sub.2] or Hg[Cl.sub.2] with [{[Li.sub.2][Te [(N-t-Bu).sub.3]]}.sub.2] in n-hexane-THF give rise to two distinctly different types of product. In the former case the complexes [Li[(THF). sub.x]][[(CdCl).sub.3][{Te[(N-t-Bu).sub.3]}.sub.2]] (7a (x = 4), 7b (x = 3)) are obtained. The tetrasolvated complex 7a is a solvent-separated ion pair. The trisolvated complex 7b is a contact ion pair in which the fourth coordination site at the [Li.sup.+] centre is occupied by one of the Cl ligands of the anion. The polycyclic anion in 7a and 7b is comprised of two tripodal [[Te[(N-t-Bu).sub.3]].sup.2-] dianions that exhibit different coordination modes to the three Cd[Cl. sup.+] units. One ligand is N,N'-chelated to all three metal centres, and each nitrogen atom bridges two Cd atoms, whereas the other is bonded in a tris-N-monodentate fashion in 7b. In 7a there is an additional weak Cd-N interaction. The reaction of Hg[Cl.sub.2] with [{[Li.sub.2][Te[(N-t-Bu).sub.3]]}.sub.2] produces the adduct [t-BuNTe [([mu]N-t-Bu).sub.2]TeN-t-Bu]Hg[Cl.sub.2] (8), in which the dimeric tellurium diimide ligand in its cis(exo,exo) configuration is N, N'-chelated to mercury. Polymeric strands parallel to the b axis are formed by weak Te***Cl interactions (3.5248(16) [Angstrom], 3.5876(15) [Angstrom]) involving both Cl atoms, but only one Te atom of the ligand. Key words: imido ligands, cadmium, mercury, tellurium.

Research has been conducted on the cyclodiphosph(III/V)azane monoselenide. Results indicate that this compound can be obtained from the comproportional reaction of equimolar amounts of H (sub)2 cdpp and H (sub)2 cdppSe (sub)2 in toluene.

The dilithiated boraamidinate complexes [{[Li.sub.2][RB[(N-t-Bu).sub. 2]]}.sub.2] (1a, R = Ph; 1b, R = t-Bu), prepared by the reaction of B[[N(H)-t-Bu].sub.3] with three equivalents of LiR, are shown by X-ray crystallography to have dimeric structures consisting of a distorted [Li.sub.4][N.sub.4] cube capped on two opposite faces by RB units. Reactions of 1a with Te[Cl.sub.4] or P[X.sub.3] (X = Cl, Br) yielded complexes PhB[([micro]-N-t-Bu).sub.2]Te[Cl.sub.2] (2) and PhB[( [micro]-N-t-Bu).sub.2]PX (4a, X = Cl; 4b, X = Br), respectively. The structures of 2 and 4b were determined by X-ray crystallography. In the solid state, complex 2 forms a dimer with weak Te ... Cl contacts (3.2411(6) [Angstrom]). Complex 4b is monomeric with a P-Br bond length of 2.3047(11) [Angstrom]. The reactions of 2 and 4a with the appropriate amounts of Li[N(H)-t-Bu] produce the monomeric tellurium imide PhB[(p.-N-t-Bu).sub.2]Te=N-t-Bu and the amido derivative PhB( [micro]-N-t-Bu)2PN(H)-t-Bu (4c), respectively. The X-ray structure of 4c was determined. Deprotonation of 4c with n-BuLi produces the dimeric monolithium derivative [{Li[PhB[([micro]-N-t-Bu).sub.2]PN-t-Bu]}.sub.2] (5), which was shown by X-ray crystallography to have a centrosymmetric structure with a central transoid [Li.sub.2][N.sub.2] ring. Key words: boraamidinates, lithium, tellurium, phosphorus, X-ray structures.

Research has been conducted on the tellurium-chalcogenide systems. The redox chemistry of these systems has been investigated via tellurium(IV) tetrachloride reactions with Li[(super)t BuN(E)P(mu-N (super)t Bu) (sub)2 P(E)N(H) (super)t Bu] and the details are reported.

Research has been conducted on the imido system chemistry which involves tellurium or antimony. The ability of the mixed antimony-tellurium systems to be generated from the tellurium diimide dimer has been tested and the results are reported.

Research has been conducted on the [(Se (sub)2 SN (sub)2)Cl] (sub)2 reaction. The preparation of this reaction has been carried out, and its characterization has been performed via X-ray crystallography, Raman spectroscopy, NMR, mass and ESP spectroscopies.

Research describes the synthesis and X-ray structure analysis of three alums containing diazasulfate dianions and the latter's ability to assume bonding modes in alkali or alkaline earth metal salts. Data reveal that all three complexes possess novel coordination modes contributed by the diazasulfate dianion.

The reaction of SeCl2 with (super t)BuNH2 in THF in various molar ratios is investigated by (super 77)Se NMR spectroscopy. The synthesis of (super t)BuNSe(mu-(super t)NBu)(sub 2)SeO and (super t)BuNSe(mu-(super t)NBu)(sub 2)SO2 and the X-ray structures of Se3(N(super t)Bu)3, (super t)BuNSe(mu-N(super t)Bu)2SO2 and (super t)BuNSe(mu-N(super t)Bu)2SeO are described.

Research has been conducted on the tellurium diimide dimer. The use of THF as a solvent to synthesize this dimer is described.

Research has been conducted on the tellurium diimide dimer coordination complexes. Mono- and dimethylation of the complexes have been demonstrated via (super)1 H and (super)125 Te NMR spectroscopy.

Deep blue (E=S) or green (E=Se) solutions are produced by the air oxidation of the cluster compounds (Li(sub2)E(NtBu)(sub3)(sub2)) in toluene. The ESR spectra comprises a septet of decuplets and simulations show that secondary hyperfine splitting occurs from interaction of the unpaired electron with equivalent Li ions. Such spectra are assigned to the radion anions SeO(NtBu)(sub2) and SeO(sub2)(NtBu).

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The reaction of M3Cl3AsF6 and M, where M is S or Se, in sulfur dioxide yields S3Cl3AsF6 and Se3Cl3AsF6. Both compounds have M3Cl3(super +) cations. X-ray diffraction and FT-IR studies help characterize these compounds. Crystal data and ab initio calculations agree with structural parameters of the cations determined by vibrational studies.

The synthesis and structural characterization of aluminum- and gallium-bridged [1.1]chromarenophanes and [1.1]molybdarenophanes are reported. These compounds are shown to contain two pairs of inner [alpha] protons that are oriented toward each other.

New symmetrical alkyl- and aryl-substituted diamidosilyl ether ligands are synthesized by using an excess amine route and a lithiated amide pathway. The kinetic parameters of the retro-Brook rearrangement reactions for N-lithio derivatives of the ligands have shown that the rate of rearrangement has increased with decreasing steric hindrance and increasing electron-donating ability of the R substituent.