Probing crystal structures and transformation reactions of ammonium molybdates by 14N MAS NMR spectroscopy

The unique high-resolution feature offered by 14N magic-angle spinning (MAS) NMR spectroscopy of ammonium ions has been used to characterize the crystal structures of various ammonium molybdates by their 14N quadrupole coupling parameters, i.e., CQ, the quadrupole coupling constant, and etaQ, the asymmetry parameter. Two polymorphs of diammonium monomolybdate, (NH4)2MoO4, recently structurally characterized by single-crystal X-ray diffraction (XRD) and named mS60 and mP60, show distinct but different 14N MAS NMR spectra from each of which two sets of characteristic 14N CQ and etaQ values have been obtained. Similarly, the well-characterized ammonium polymolybdates (NH4)2Mo2O7, (NH4)6Mo7O24.4H2O, and (NH4)6Mo8O27.4H2O also give rise to distinct and characteristic 14N MAS NMR spectra. In particular, it is noted that simulation of the experimental (NH4)6Mo7O24.4H2O spectrum requires an iterative fit with six independent NH4+ sites. For the slow spinning frequencies employed (nu(r) = 1500-3000 Hz), all 14N MAS NMR spectra of the ammonium molybdates in this study are fingerprints of their identity. These different 14N MAS NMR fingerprints are shown to be an efficient tool in qualitative and quantitative assessment of the decomposition of (NH4)2MoO4 in humid air. Finally, by a combination of the 14N and 95Mo MAS NMR experiments performed here, it has become clear that a recent report of the 95Mo MAS spectra and data for the mS60 and mP60 polymorphs of (NH4)2MoO4 are erroneous because the sample examined had decomposed to (NH4)2Mo2O7.     

Liquid-liquid distribution of ion-associates of dichlorocuprate(I) with quaternary ammonium counter-ions

The dichlorocuprate(I) anion CuCl(-)(2) can be extracted as its ion-associates Q(+).CuCl(-)(2) with quaternary ammonium cations (Q(+)) into chloroform. The extraction constants K(ex) have been determined, and the log K(ex) values found for the various counter-ions used are 1.93 for (C(3)H(7))(4)N(+), 4.10 for (C(4)H(9))(4)N(+), 6.57 for (C(5)H(11))(4)N(+), 1.57 for C(8)H(17)N(+) (CH(3))(3), 2.83 for C(10)H(21)N(+) (CH(3))(3) 4.12 for C(12)H(25)N(+) (CH(3))(3) and 5.21 for C(14)H(29)N(+)(CH(3))(3), respectively. A linear relationship was found between log K(ex) and the total number of carbon atoms in Q(+); from the slope of the line, the contribution of a methylene group to log K(ex) was calculated to be 0.59. The extractability with alkyltrimethylammonium cations was larger than that with symmetrical tetra-alkylammonium cations and the difference in log K(ex) for two cations (one of each type) with the same number of carbon atoms was about 0.4. From the extraction constants obtained, the extractability of CuCl(-)(2) was found to lie between that of ReO(-)(4) and ClO(-)(4).     

1H NMR study on pre-micellization of quaternary ammonium gemini surfactants

Two quaternary ammonium Gemini surfactant series, 12-s-12, ([C(12)H(25)N+ (CH(3))(2)](2)(CH(2))(s).(2)Br(-)) and 14-s-14 ([C(14)H(29)N(+)(CH(3))(2)](2)(CH(2))(s).(2)Br(-)), where s = 2, 3, and 4, have been studied by the use of (1)H NMR in aqueous solution at concentrations below their critical micelle concentrations (CMC) at 25 degrees C. The appearance of a second set of peaks for the 14-s-14 series and the changes in chemical shifts, line widths, and line shapes of the 12-s-12 series with increasing concentration below the CMC are interpreted as evidence for the formation of premicelle aggregates (oligomers) that appear at approximately one-half their CMC values. Self-diffusion coefficients (D) and transverse relaxation times (T(2)) have also been detected and support the results obtained by (1)H NMR.     

Remarkable reactions of cyclooctatetraene diiron-bridging carbyne complexes with amino and amido compounds: nucleophilic addition to and breaking of the cyclooctatetraene ring

The reactions of the cationic, diiron-bridging carbyne complexes [Fe(2)(mu-CAr)(CO)(4)(eta(8)-C(8)H(8))]BF(4) (1, Ar=C(6)H(5); 2, Ar=p-CH(3)C(6)H(4); 3, Ar=p-CF(3)C(6)H(4)) with LiN(C(6)H(5))(2) in THF at low temperature gave novel N-nucleophilic-addition products, namely, the neutral, diiron-bridging carbyne complexes [Fe(2)(mu-CAr)(CO)(4)(eta(7)-C(8)H(8)N(C(6)H(5))(2))] (4, Ar=C(6)H(5); 5, Ar=p-CH(3)C(6)H(4); 6, Ar=p-CF(3)C(6)H(4))). Cationic bridging carbyne complexes 1-3 react with (C(2)H(5))(2)NH, (iC(3)H(7))(2)NH, and (C(6)H(11))(2)NH under the same conditions with ring cleavage of the COT ligand to produce the novel diiron-bridging carbene inner salts [Fe(2)[mu-C(Ar)C(8)H(8)NR(2)](CO)(4)] (7, Ar=C(6)H(5), R=C(2)H(5); 8, Ar=p-CH(3)C(6)H(4), R=C(2)H(5); 9, Ar=p-CF(3)C(6)H(4), R=C(2)H(5); 10, Ar=C(6)H(5), R=iC(3)H(7); 11, Ar=p-CH(3)C(6)H(4), R=iC(3)H(7); 12, Ar=p-CF(3)C(6)H(4), R=iC(3)H(7); 13, Ar=C(6)H(5), R=C(6)H(11); 14, Ar=p-CH(3)C(6)H(4), R=C(6)H(11), 15, Ar=p-CF(3)C(6)H(4), R=C(6)H(11)). Piperidine reacts similarly with cationic carbyne complex 3 to afford the corresponding bridging carbene inner salt [Fe(2)[mu-C(Ar)C(8)H(8)N(CH(2))(5)](CO)(4)] (16). Compound 9 was transformed into a new diiron-bridging carbene inner salt 17, the trans isomer of 9, by heating in benzene. Unexpectedly, the reaction of C(6)H(5)NH(2) with 2 gave a novel COT iron-carbene complex [Fe(2)[=C(C(6)H(4)CH(3)-p)NHC(6)H(5)](mu-CO)(CO)(3)(eta(8)-C(8)H(8))] (18). However, the analogous reactions of 2-naphthylamine with 2 and of p-CF(3)C(6)H(4)NH(2) with 3 produce novel chelated iron-carbene complexes [Fe(2)[=C(C(6)H(4)CH(3)-p)NC(10)H(7)](CO)(4)(eta(2):eta(3):eta(2)-C(8)H(9))] (19) and [Fe(2)[=C(C(6)H(4)CF(3)-p)NC(6)H(4)CF(3)-p](CO)(4)(eta(2):eta(3):eta(2)-C(8)H(9))] (20), respectively. Compound 18 can also be transformed into the analogous chelated iron-carbene complex [Fe(2)[=C(C(6)H(4)CH(3)-p)NC(6)H(5)](CO)(4)(eta(2):eta(3):eta(2)-C(8)H(9))] (21). The structures of complexes 6, 9, 15, 17, 18, and 21 have been established by X-ray diffraction studies.     

Imido Complexes Derived from the Reactions of Niobium and Tantalum Pentachlorides with Primary Amines: Relevance to the Chemical Vapor Deposition of Metal Nitride Films

Reactions of niobium and tantalum pentachlorides with tert-butylamine (>/=6 equiv) in benzene afford the dimeric imido complexes [NbCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2) (90%) and [TaCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2) (79%). The niobium complex exists as two isomers in solution, while the tantalum complex is composed of three major isomers and at least two minor isomers. Analogous treatments with isopropylamine (>/=7 equiv) give the monomeric complexes NbCl(2)(N(i)Pr)(NH(i)Pr)(NH(2)(i)Pr)(2) (84%) and TaCl(2)(N(i)Pr)(NH(i)Pr)(NH(2)(i)Pr)(2) (84%). The monomeric complexes are unaffected by treatment with excess isopropylamine, while the dimeric complexes are cleaved to the monomers MCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)(2) upon addition of excess tert-butylamine in chloroform solution. Treatment of niobium and tantalum pentachlorides with 2,6-diisopropylaniline affords insoluble precipitates of [NH(3)(2,6-(CH(CH(3))(2))(2)C(6)H(3))](2)[NbCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] (100%) and [NH(3)(2,6-(CH(CH(3))(2))(2)C(6)H(3))](2)[TaCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] (100%), which react with 4-tert-butylpyridine to afford the soluble complexes [4-t-C(4)H(9)C(5)H(4)NH](2)[NbCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] (45%) and [4-t-C(4)H(9)C(5)H(4)NH](2)[TaCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] (44%). Sublimation of [NbCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2), MCl(2)(N(i)Pr)(NH(i)Pr)(NH(2)(i)Pr)(2), and [NH(3)(2,6-(CH(CH(3))(2))(2)C(6)H(3))](2)[MCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] leads to decomposition to give [MCl(3)(NR)(NH(2)R)](2) as sublimates (32-49%), leaving complexes of the proposed formulation MCl(NR)(2) as nonvolatile residues. By contrast, [TaCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2) sublimes without chemical reaction. Analysis of the organic products obtained from thermal decomposition of [NbCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2) showed isobutylene and tert-butylamine in a 2.2:1 ratio. Mass spectra of [NbCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2), [TaCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2), and [NbCl(3)(N(i)Pr)(NH(2)(i)Pr)](2) showed the presence of dimeric imido complexes, monomeric imido complexes, and nitrido complexes, implying that such species are important gas phase species in CVD processes utilizing these molecular precursors. The crystal structures of [4-t-C(4)H(9)C(5)H(4)NH](2)[NbCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))], [NbCl(3)(N(i)Pr)(NH(2)(i)Pr)](2), [NbCl(3)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))(NH(2)(2,6-(CH(CH(3))(2))(2)C(6)H(3)))](2), and [TaCl(3)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))(NH(2)(2,6-(CH(CH(3))(2))(2)C(6)H(3)))](2) were determined. [4-t-C(4)H(9)C(5)H(4)NH](2)[NbCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] crystallizes in the space group P2(1)/c with a = 12.448(3) ?, b = 10.363(3) ?, c = 28.228(3) ?, beta = 94.92(1) degrees, V = 3628(5) ?(3), and Z = 4. [NbCl(3)(N(i)Pr)(NH(2)(i)Pr)](2) crystallizes in the space group P2(1)/c with a = 9.586(4) ?, b = 12.385(4) ?, c = 11.695(4) ?, beta = 112.89(2) degrees, V = 1279.0(6) ?(3), and Z = 2. [NbCl(3)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))(NH(2)(2,6-(CH(CH(3))(2))(2)C(6)H(3)))](2) crystallizes in the space group P2(1)/n with a = 10.285(3) ?, b = 11.208(3) ?, c = 23.867(6) ?, beta = 97.53 degrees, V = 2727(1) ?(3), and Z = 2. [TaCl(3)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))(NH(2)(2,6-(CH(CH(3))(2))(2)C(6)H(3)))](2) crystallizes in the space group P2(1)/n with a = 10.273(1) ?, b = 11.241(2) ?, c = 23.929(7) ?, beta = 97.69(2) degrees, V = 2695(2) ?(3), and Z = 2. These findings are discussed in the context of niobium and tantalum nitride film depositions from molecular precursors.     

Reactions of manganese and rhenium complexes with organic azides: preparation of tetraazabutadiene derivatives

Azide complexes [M(RN(3))(CO)(3)P(2)]BPh(4)[M = Mn, Re; R = C(6)H(5)CH(2), 4-CH(3)C(6)H(4)CH(2), C(6)H(5), 4-CH(3)C(6)H(4), C(5)H(9); P = PPh(OEt)(2), PPh(2)(OEt)] were prepared by allowing tricarbonyl MH(CO)(3)P(2) hydride complexes to react first with Br?nsted acid (HBF(4), CF(3)SO(3)H) and then with organic azide in the dark. In sunlight the reaction yielded tetraazabutadiene [M(eta(2)-1,4-R(2)N(4))(CO)(2)P(2)]BPh(4) complexes or, with benzyl azide, imine [M{eta(1)-NH[double bond, length as m-dash]C(H)Ar}(CO)(3)P(2)]BPh(4)(Ar = C(6)H(5), 4-CH(3)C(6)H(4)) derivatives. Tetraazabutadiene [M(eta(2)-1,4-R(2)N(4))(CO)(2)P(2)]BPh(4) complexes were also prepared by reacting dicarbonyl MH(CO)(2)P(3) species first with Br?nsted acid and then with an excess of organic azide. Complexes were characterised spectroscopically (IR, (1)H, (31)P, (13)C, (15)N NMR data) and by the X-ray crystal structure determination of complex [Re{eta(2)-1,4-(C(6)H(5)CH(2))(2)N(4)}(CO)(2){PPh(OEt)(2)}(2)]BPh(4)(). Strong evidence for coordination of the organic azide was obtained from the (15)N NMR spectra of labelled [M(C(6)H(5)CH(2)(15)NN(15)N)(CO)(3)P(2)]BPh(4) derivatives.     

Assembly of hybrid organic-organometallic materials through mechanochemical acid-base reactions

Manual grinding of the organometallic complex [Fe(eta(5)-C(5)H(4)COOH)(2)] with a number of solid bases, namely 1,4-diazabicyclo[2.2.2]octane, C(6)H(12)N(2), 1,4-phenylenediamine, p-(NH(2))(2)C(6)H(4), piperazine, HN(C(2)H(4))(2)NH, trans-1,4-cyclohexanediamine, p-(NH(2))(2)C(6)H(10), and guanidinium carbonate [(NH(2))(3)C](2)[CO(3)], generates quantitatively the corresponding adducts, [HC(6)H(12)N(2)][Fe(eta(5)-C(5)H(4)COOH)(eta(5)-C(5)H(4)COO)] (1), [HC(6)H(8)N(2)][Fe(eta(5)-C(5)H(4)COOH)(eta(5)-C(5)H(4)COO)] (2), [H(2)C(4)H(10)N(2)][Fe(eta(5)-C(5)H(4)COO)(2)] (3), [H(2)C(6)H(14)N(2)][Fe(eta(5)-C(5)H(4)COO)(2)].2 H(2)O, (4.2 H(2)O), and [C(NH(2))(3)](2)[Fe(eta(5)-C(5)H(4)COO)(2)].2 H(2)O, (5.2 H(2)O), respectively. Crystallization from methanol in the presence of seeds of the ground sample allows the growth of single crystals of these adducts; therefore we were able to determine the structures of the adducts by single-crystal X-ray diffraction. This information was used in turn to identify and characterize the polycrystalline materials obtained by the grinding process. In the case of [HC(6)N(2)H(12)][Fe(eta(5)-C(5)H(4)COOH)(eta(5)-C(5)H(4)COO)] (1), the base can be removed by mild treatment regenerating the starting dicarboxylic acid, while in all other cases decomposition is observed. The solid-solid processes described herein imply molecular diffusion through the lattice, breaking and reassembling of hydrogen-bonded networks, and proton transfer from acid to base.     

Organolanthanide-catalyzed intramolecular hydroamination/cyclization/bicyclization of sterically encumbered substrates. Scope, selectivity, and catalyst thermal stability for amine-tethered unactivated 1,2-disubstituted alkenes

This paper reports the organolanthanide-catalyzed intramolecular hydroamination/cyclization of amine-tethered unactivated 1,2-disubstituted alkenes to afford the corresponding mono- and disubstituted pyrrolidines and piperidines using coordinatively unsaturated complexes of the type (eta(5)-Me(5)C(5))(2)LnCH(TMS)(2) (Ln = La, Sm), [Me(2)Si(eta(5)-Me(4)C(5))(2)]SmCH(TMS)(2), and [Me(2)Si(eta(5)-Me(4)C(5))((t)BuN)]LnE(TMS)(2) (Ln = Sm, Y, Yb, Lu; E = N, CH) as precatalysts. [Me(2)Si(eta(5)-Me(4)C(5))((t)BuN)]LnE(TMS)(2) mediates intramolecular hydroamination/cyclization of sterically demanding amino-olefins to afford disubstituted pyrrolidines in high diastereoselectivity (trans/cis = 16/1) and good to excellent yield. In addition, chiral C(1)-symmetric organolanthanide catalysts of the type [Me(2)Si(OHF)(CpR*)]LnN(TMS)(2) (OHF = eta(5)-octahydrofluorenyl; Cp = eta(5)-C(5)H(3); R* = (-)-menthyl; Ln = Sm, Y), and [Me(2)Si(eta(5)-Me(4)C(5))(CpR*)]SmN(TMS)(2) (Cp = eta(5)-H(3)C(5); R* = (-)-menthyl) mediate asymmetric intramolecular hydroamination/cyclization of amines bearing internal olefins and afford chiral 2-substituted piperidine and pyrrolidine in enantioselectivities as high as 84:16 er at 60 degrees C. The substrate of the structure NH(2)CH(2)CMe(2)CH(2)CH=CH(CH(2))(2)CH=CH(2) is regiospecifically bicyclized by [Me(2)Si(eta(5)-Me(4)C(5))((t)BuN)]LnE(TMS)(2) to the corresponding indolizidine skeleton in good yield and high diastereoselectivity. Thermolysis of (eta(5)-Me(5)C(5))(2)LaCH(TMS)(2) in cyclohexane-d(12) at 120 degrees C rapidly releases CH(2)(SiMe(3))(2) and leads to possible formation of fulvene (eta(6)-Me(4)C(5)CH(2)-) species. The thermolysis product readily reverts to active catalysts upon protonolysis by substrate and exhibits the same catalytic activity as the (eta(5),eta(1)-Me(5)C(5))(2)LaCH(TMS)(2) precatalyst at 120 degrees C in the cyclization of cis-2,2-dimethylhept-5-enylamine. Catalytically-active lanthanide-amido complexes (eta(5)-Me(5)C(5))(2)La(NHR)(NH(2)R)(n) and [Me(2)Si(eta(5)-Me(4)C(5))((t)BuN)]Sm(NHR)(NH(2)R)(n) are shown to be thermally robust species.     

Reaction of an osmium(VI) nitrido complex with cyanide: formation and reactivity of an osmium(III) hydrogen cyanamide complex

Reaction of [Os(VI)(N)(L(1))(Cl)(OH(2))] (1) with CN(-) under various conditions affords (PPh(4))[Os(VI)(N)(L(1))(CN)(Cl)] (2), (PPh(4))(2)[Os(VI)(N)(L(2))(CN)(2)] (3), and a novel hydrogen cyanamido complex, (PPh(4))(2)[Os(III){N(H)CN}(L(3))(CN)(3)] (4). Compound 4 reacts readily with both electrophiles and nucleophiles. Protonation and methylation of 4 produce (PPh(4))[Os(III)(NCNH(2))(L(3))(CN)(3)] (5) and (PPh(4))[Os(III)(NCNMe(2))(L(3))(CN)(3)] (6), respectively. Nucleophilic addition of NH(3), ethylamine, and diethylamine readily occur at the C atom of the hydrogen cyanamide ligand of 4 to produce osmium guanidine complexes with the general formula [Os(III){N(H)C(NH(2))NR(1)R(2)}(L(3))(CN)(3)](-) , which have been isolated as PPh(4) salts (R(1) = R(2) = H (7); R(1) = H, R(2) = CH(2)CH(3) (8); R(1) = R(2) = CH(2)CH(3) (9)). The molecular structures of 1-5 and 7 and 8 have been determined by X-ray crystallography.     

Partial proton transfer in a molecular complex: assessments from both the donor and acceptor points of view

Microwave spectra have been observed for the gas phase complexes (CH(3))(3)(14)N-H(14)NO(3) and (CH(3))(3)(15)N-H(14)NO(3) and rotational and nuclear quadrupole coupling constants are reported. The structure and binding energy have also been calculated at the MP2 level of theory using the 6-311++G(d,p) and 6-311++G(2df,2pd) basis sets both with and without corrections for basis set superposition error. The HNO(3) forms a near-linear hydrogen bond to the amine nitrogen with a rather short hydrogen bond distance of about 1.5-1.6 ? (depending on the basis set and method of computation). The C(3) axis of the trimethylamine lies in the plane of the nitric acid. For both the H(14)NO(3) and the (CH(3))(3)(14)N moieties of the parent species, the component of the nuclear quadrupole coupling tensor perpendicular to the molecular symmetry plane, χ(cc), is sensitive to the electronic structure at the corresponding nitrogen but independent of relative orientation within the plane. Its value, therefore, provides a convenient experimental measure of the degree of proton transfer within the complex. For the HNO(3), χ(cc) lies 62% of the way between those of free HNO(3) and aqueous NO(3)(-), indicating a substantial degree of proton transfer. A similar comparison of the quadrupole coupling constant of (CH(3))(3)N in the (CH(3))(3)N-HNO(3) complex with those of free (CH(3))(3)N and (CH(3))(3)NH(+) indicates only about 31% proton transfer, about half that determined from the HNO(3) coupling constant. Though surprising at first, this disparity is to be expected if the quadrupole coupling constants vary nonlinearly with the position of the proton relative to the donor and acceptor atoms. Calculations of the (14)N nuclear quadrupole coupling constants as a function of proton position using density functional theory are reported and confirm that this is the case. We suggest that when proton transfer is assessed according to changes in individual monomer molecular properties, the overall process may be best described in terms of a dual picture involving proton release by the acid and proton acquisition by the base.     

Solution structures and dynamic properties of chelated d(0) metal olefin complexes [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))(+) (R = H, Me): Models for the [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(R')(olefin)(+) intermediates in "constrained geometry" catalysts.

To model the Ti-olefin interaction in the putative [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(R')(olefin)(+) intermediates in "constrained geometry" Ti-catalyzed olefin polymerization, chelated alkoxide olefin complexes [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))(+) have been investigated. The reaction of [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(2) (1a,b; R = H, Me) with HOCMe(2)CH(2)CH(2)CH=CH(2) yields mixtures of [eta(5)-C(5)R(4)SiMe(2)NH(t)Bu]TiMe(2)(OCMe(2)CH(2)CH(2)CH=CH(2)) (2a,b) and [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(OCMe(2)CH(2)CH(2)CH=CH(2)) (3a,b). The reaction of 2a/3a and 2b/3b mixtures with B(C(6)F(5))(3) yields the chelated olefin complexes [[eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][MeB(C(6)F(5))(3)] (4a,b; 71 and 89% NMR yield). The reaction of 2b/3b with [Ph(3)C][B(C(6)F(5))(4)] yields [[eta(5): eta(1)-C(5)Me(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][B(C(6)F(5))(4)] (5b, 88% NMR yield). NMR studies establish that 4a,b and 5b exist as mixtures of diastereomers (isomer ratios: 4a/4a', 62/38; 4b/4b', 75/25; 5b/5b', 75/25), which differ in the enantioface of the olefin that is coordinated. NMR data for these d(0) metal olefin complexes show that the olefin coordinates to Ti in an unsymmetrical fashion primarily through C(term) such that the C=C pi bond is polarized with positive charge buildup on C(int). Dynamic NMR studies show that 4b/4b' undergoes olefin face exchange by a dissociative mechanism which is accompanied by fast inversion of configuration at Ti ("O-shift") in the olefin-dissociated intermediate. The activation parameters for the conversion of 4b to 4b' (i.e., 4b/4b' face exchange) are: DeltaH = 17.2(8) kcal/mol; DeltaS = 8(1) eu. 4a/4a' also undergoes olefin face exchange but with a lower barrier (DeltaH = 12.2(9) kcal/mol; DeltaS = -2(3) eu), for the conversion of 4a to 4a'.     

Refinement of borate structures from 11B MAS NMR spectroscopy and density functional theory calculations of 11B electric field gradients

The refinement of borate structures using DFT calculations combined with experimental (11)B quadrupole coupling parameters from solid-state NMR spectroscopy is presented. The (11)B electric field gradient (EFG) tensors, calculated using the WIEN2k software for trigonal and tetrahedral boron sites in a series of model compounds, exhibit a convincing linear correlation with the quadrupole coupling tensor elements, determined from (11)B MAS NMR spectra of the central or satellite transitions. The model compounds include Li(2)B(4)O(7), Mg(2)B(2)O(5), Mg(3)B(2)O(6), NH(4)B(C(6)H(5))(4), and colemanite (CaB(3)O(4)(OH)(3).H(2)O). The (11)B quadrupole moment, Q = 0.0409 +/- 0.0002 barn, derived from the linear correlation, is in excellent agreement with the accepted value for Q((11)B). This demonstrates that DFT (WIEN2k) calculations can provide precise (11)B quadrupole coupling parameters on an absolute scale. On the other hand, DFT calculations based on the reported crystal structures for datolite (CaBSiO(4)(OH)) and danburite (CaB(2)Si(2)O(8)) cannot reproduce the experimental (11)B quadrupole coupling parameters to the same high precision. However, optimization of these structures by minimization of the forces between the atoms (obtained by DFT) results in a significant improvement between the calculated and experimental (11)B quadrupole coupling parameters, which indicates that reliable refinements of the borate structures are obtained by this method. Finally, the DFT calculations also provide important structural information about the sign and orientation of the EFG tensor elements in the crystal frame, a kind of information that cannot be achieved from (11)B NMR experiments on powdered samples.     

Reactivity of Mo(PMe3)6 towards benzothiophene and selenophenes: new pathways relevant to hydrodesulfurization

Mo(PMe(3))(6) cleaves a C-S bond of benzothiophene to give (kappa(2)-CHCHC(6)H(4)S)Mo(PMe(3))(4), which rapidly isomerizes to the olefin-thiophenolate and 1-metallacyclopropene-thiophenolate complexes, (kappa(1),eta(2)-CH(2)CHC(6)H(4)S)Mo(PMe(3))(3)(eta(2)-CH(2)PMe(2)) and (kappa(1),eta(2)-CH(2)CC(6)H(4)S)Mo(PMe(3))(4). The latter two molecules result from a series of hydrogen transfers and are differentiated according to whether the termini of the organic fragments coordinate as olefin or eta(2)-vinyl ligands, respectively. The reactions between Mo(PMe(3))(6) and selenophenes proceed differently from those of the corresponding thiophenes. For example, whereas Mo(PMe(3))(6) reacts with thiophene to give eta(5)-thiophene and butadiene-thiolate complexes, (eta(5)-C(4)H(4)S)Mo(PMe(3))(3) and (eta(5)-C(4)H(5)S)Mo(PMe(3))(2)(eta(2)-CH(2)PMe(2)), selenophene affords the metallacyclopentadiene complex [(kappa(2)-C(4)H(4))Mo(PMe(3))(3)(Se)](2)[Mo(PMe(3))(4)] in which the selenium has been completely abstracted from the selenophene moiety. Likewise, in addition to (kappa(1),eta(2)-CH(2)CC(6)H(4)Se)Mo(PMe(3))(4) and (kappa(1),eta(2)-CH(2)CHC(6)H(4)Se)Mo(PMe(3))(3)(eta(2)-CH(2)PMe(2)), which are counterparts of the species observed in the benzothiophene reaction, the reaction of Mo(PMe(3))(6) with benzoselenophene yields products resulting from C-C coupling, namely [kappa(2),eta(4)-Se(C(6)H(4))(CH)(4)(C(6)H(4))Se]Mo(PMe(3))(2) and [mu-Se(C(6)H(4))(CH)C(CH)(2)(C(6)H(4))](mu-Se)[Mo(PMe(3))(2)][Mo(PMe(3))(2)H].     

Novel organometallic building blocks for molecular crystal engineering. Part 4. Synthesis and characterization of mono- and bis-amido derivatives of [Co(III)(eta5-C5H4COOH)2]+ and their utilization as ligands

The synthesis and structural characterization of the hexafluorophosphate salts of the substituted bis-amido molecular complexes [Co(III)(eta5-C5H4CONHC4H3N2)2]+ (1), [Co(III)(eta5-C5H4CONHCH2C5H4N)2]+ (2), [Co(III)(eta5-C5H4CON(C5H4N)2)2]+ (3), and of the amido-carboxyl complexes [Co(III)(eta5-C5H4CON(C5H4N)2)(eta5-C5H4COOH)]+ (4), and [Co(III)(eta5-C5H4CONHC2N3(C5H4N)2)(eta5-C5H4COOH)]+ (5) are reported. The pyridyl and pyrazine substituted amido ligands on the sandwich cores have been chosen because they allow both coordination to metal centres and participation in hydrogen bonding. The hydrogen bonding interactions established by the family of complexes in the solid state has been investigated. The utilization of complex 5 for the preparation of the complex of complexes[Cd(NO3)2{Co(III)(eta5-C5H4CONHC2N3(C5H4N)(C5H4NH))(eta5-C5H4COOH)}2]6+ (6) is reported as a first example of the potential of the substituted mono-and bis-amides as ligands. The isolation and structural characterization of the carbonyl chloride cation [Co(III)(eta5-C5H4COCl)2]+ (7) as its tetrachloro cobaltate anion salt is also described.     

A novel series of materials composed of arrays of vanadium oxide container molecules, [V18O42(X)] (X = H2O,Cl-, Br-): synthesis and characterization of [M2(H2N(CH2)2NH2)5][(M(H2N(CH2)2NH2)2]2V18O42(X)]. 9H2O (M = Zn,Cd)

The synthesis and characterization of the novel systems [Zn(2)(H(2)N(CH(2))(2)NH(2))(5)][(Zn(H(2)N(CH(2))(2)NH(2))(2))(2)V(18)O(42)(H(2)O)].9H(2)O (1), [Cd(2)(H(2)N(CH(2))(2)NH(2))(5)][(Cd(H(2)N(CH(2))(2)NH(2))(2))(2)V(18)O(42)(Br)].9H(2)O (2), and [Zn(2)(H(2)N(CH(2))(2)NH(2))(5)][(Zn(H(2)N(CH(2))(2)NH(2))(2))(2)V(18)O(42)(Cl)].9H(2)O (3) have been described. These materials represent a new class of solids that have been prepared by combining conventional coordination compounds with spherical polyoxovanadate clusters. The isomorphous structures of these hybrid solids consist of two-dimensional arrays of container cluster molecules [V(18)O(42)(X)] (X = H(2)O, Br-, Cl-) interlinked by the transition metal complex moieties [M(H(2)N(CH(2))(2)NH(2))(2)] (M = Zn, Cd). These compounds contain an unprecedented complex cation, [M(2)(H(2)N(CH(2))(2)NH(2))(5)](4+). Crystal data for 1: C(9)H(46)N(9)O(26)V(9)Zn(2), monoclinic space group P2(1)/m (No. 11), a = 12.3723(7) A, b = 20.9837(11) A, c = 15.8379(8) A, beta = 97.3320(10) degrees, Z = 4.     

Synthesis and Evaluation of Thioether-Based Tris-Melamines as Components of Self-Assembled Aggregates Based on the CA.M Lattice

Two new tris-melamine derivatives, triazine-thio-M(3) (5) (C(3)N(3)-2,4,6-[SCH(2)C(6)H(4)-3-N(CH(2)C(6)H(4)-4-C(CH(3))(3))COC(6)N(3)-2-NHC(3)N(3)(NH(2))(NHCH(2)CH(2)C(CH(3))(3))-5-Br](3)) and benzene-thio-M(3) (6) (C(6)H(3)-1,3,5-[SCH(2)C(6)H(4)-3-N(CH(2)C(6)H(4)-4-C(CH(3))(3))COC(6)H(3)-2-NHC(3)N(3)(NH(2))(NHCH(2)CH(2)C(CH(3))(3))-5-Br](3)), were synthesized by reactions of 2,4,6-trithiocyanuric acid and 1,3,5-trimercaptobenzene with a bromobenzyl melamine derivative 19 (BrCH(2)C(6)H(4)-3-N(CH(2)C(6)H(4)-4-C(CH(3))(3))COC(6)H(3)-2-NHC(3)N(3)(NH(2))(NHCH(2)CH(2)C(CH(3))(3))-5-Br). These two compounds formed stable and structurally well-defined 1 + 3 supramolecular aggregates with neohexyl isocyanurate (R'CA) (9) as shown by NMR spectroscopy and gel permeation chromatography. (1)H NMR competition experiments indicated that the stability of triazine-thio-M(3).(R'CA)(3) (1) was similar to that of benzene-thio-M(3).(R'CA)(3) (2). The order of stabilities of tris-melamine-based 1 + 3 complexes was hubM(3).(R'CA)(3) (3) > triazine-thio-M(3).(R'CA)(3) (1) approximately benzene-thio-M(3).(R'CA)(3) (2) > flexM(3).(R'CA)(3) (4). Computational simulations were also carried out on triazine-thio-M(3).(R'CA)(3) and hubM(3).(R'CA)(3) fully solvated in CHCl(3). Values of DP (the deviation from planarity of the cyanuric acid and melamine rosette) obtained from these simulations correlated correctly with the observed stabilities and suggested a structural reason why triazine-thio-M(3).(R'CA)(3) was less stable than hubM(3).(R'CA)(3).     

Binuclear half-sandwich cobalt(III) and rhodium(III) ortho-carboranedichalocogenolato complexes with ether chain-bridged bis(cyclopentadienyl) ligand

1, 1'-(3-Oxapentamethylene)dicyclopentadiene [O(CH(2)CH(2)C(5)H(5))(2)], containing a flexible chain-bridged group, was synthesized by the reaction of sodium cyclopentadienide with bis(2-chloroethyl) ether through a slightly modified literature procedure. Furthermore, the binuclear cobalt(III) complex O[CH(2)CH(2)(eta(5)-C(5)H(4))Co(CO)I(2)](2) and insoluble polynuclear rhodium(III) complex {O[CH(2)CH(2)(eta(5)-C(5)H(4))RhI(2)](2)}(n) were obtained from reactions of with the corresponding metal fragments and they react easily with PPh(3) to give binuclear metal complexes, O[CH(2)CH(2)(eta(5)-C(5)H(4))Co(PPh(3))I(2)](2) and O[CH(2)CH(2)(eta(5)-C(5)H(4))Rh(PPh(3))I(2)](2), respectively. Complexes react with bidentate dilithium dichalcogenolato ortho-carborane to give eight binuclear half-sandwich ortho-carboranedichalcogenolato cobalt(III) and rhodium(III) complexes O[CH(2)CH(2)(eta(5)-C(5)H(4))Co(PPh(3))(E(2)C(2)B(10)H(10))](2) (E = S and Se), O[CH(2)CH(2)(eta(5)-C(5)H(4))](2)Co(2)(E(2)C(2)B(10)H(10)) (E = S and Se), O[CH(2)CH(2)(eta(5)-C(5)H(4))Co(E(2)C(2)B(10)H(10))](2) (E = S and Se and O[CH(2)CH(2)(eta(5)-C(5)H(4))Rh(PPh(3))(E(2)C(2)B(10)H(10))](2) (E = S and Se). All complexes have been characterized by elemental analyses, NMR spectra ((1)H, (13)C, (31)P and (11)B NMR) and IR spectroscopy. The molecular structures were determined by X-ray diffractometry.     

Melem (2,5,8-triamino-tri-s-triazine), an important intermediate during condensation of melamine rings to graphitic carbon nitride: synthesis,structure determination by X-ray powder diffractometry,solid-state NMR,and theoretical studies

Single-phase melem (2,5,8-triamino-tri-s-triazine) C(6)N(7)(NH(2))(3) was obtained as a crystalline powder by thermal treatment of different less condensed C-N-H compounds (e.g., melamine C(3)N(3)(NH(2))(3), dicyandiamide H(4)C(2)N(4), ammonium dicyanamide NH(4)[N(CN)(2)], or cyanamide H(2)CN(2), respectively) at temperatures up to 450 degrees C in sealed glass ampules. The crystal structure was determined ab initio by X-ray powder diffractometry (Cu K alpha(1): P2(1)/c (No. 14), a = 739.92(1) pm, b = 865.28(3) pm, c = 1338.16(4) pm, beta = 99.912(2) degrees, and Z = 4). In the solid, melem consists of nearly planar C(6)N(7)(NH(2))(3) molecules which are arranged into parallel layers with an interplanar distance of 327 pm. Detailed (13)C and (15)N MAS NMR investigations were performed. The presence of the triamino form instead of other possible tautomers was confirmed by a CPPI (cross-polarization combined with polarization inversion) experiment. Furthermore, the compound was characterized using mass spectrometry, vibrational (IR, Raman), and photoluminescence spectroscopy. The structural and vibrational properties of molecular melem were theoretically studied on both the B3LYP and the MP2 level. A structural optimization in the extended state was performed employing density functional methods utilizing LDA and GGA. A good agreement was found between the observed and calculated structural parameters and also for the vibrational frequencies of melem. According to temperature-dependent X-ray powder diffractometry investigations above 560 degrees C, melem transforms into a graphite-like C-N material.     

Direct solid-state NMR spectroscopic evidence for the NH4AlF4 crystalline phase derived from zeolite HY dealuminated with ammonium hexafluorosilicate

Multinuclear (1)H, (19)F, and (27)Al MAS (magic angle spinning) and corresponding 2D HETCOR (heteronuclear correlation) NMR spectroscopy, in combination with powder XRD measurements, provide the direct evidence for the NH(4)AlF(4) crystalline phase, which was formed from zeolite HY dealuminated with an aqueous (NH(4))(2)SiF(6) solution at 80 degrees C. The NH(4)AlF(4) crystalline phase exhibits a characteristic second-order quadrupolar-induced (27)Al NMR line shape spreading from 0 to -90 ppm (in a magnetic field of 11.7 T) and two (19)F resonances at -151 and -166 ppm in the (19)F NMR spectrum. An( 27)Al quadrupolar coupling constant (C(Q)) of 9.5 MHz and an asymmetry parameter (eta) of 0.1 were identified, for the first time, for the NH(4)AlF(4) crystalline phase observed. On the basis of the (19)F{(27)Al} TRAPDOR (transfer population in double resonance) NMR results, the (19)F resonances at -151 and -166 ppm are therefore assigned to (19)F spins associated with the fluorines in the terminal Al-F and the bridging Al-F-Al groups, respectively.     

Homolysis of the Ln-N (Ln = Yb, Eu) bond. Synthesis, structural characterization and catalytic activity of ytterbium(II) and europium(II) complexes with methoxyethyl functionalized indenyl ligands

The interaction of methoxyethyl functionalized indene compounds (C(9)H(6)-1-R-3-CH(2)CH(2)OMe, R =t-BuNHSiMe(2)(1), Me(3)Si (2), H (3)) with [(Me(3)Si)(2)N](3)Ln(mu-Cl)Li(THF)(3)(Ln=Yb (4), Eu (5)) produced a series of new ytterbium(II) and europium(II) complexes via tandem silylamine elimination/homolysis of the Ln-N (Ln=Yb, Eu) bond. Treatment of the lanthanide(III) amides [(Me(3)Si)(2)N](3)Ln(mu-Cl)Li(THF)(3)(Ln=Yb (4), Eu (5) with 2 equiv. of, 1,2 and 3, respectively, produced, after workup, the ytterbium(II) complexes [eta5:eta1-Me(2)Si(MeOCH(2)CH(2)C(9)H(5))(NHBu-t)](2)Yb(II) (6), (eta5:eta1-MeOCH(2)CH(2)C(9)H(5)SiMe(3))(2)Yb(II) (7), (eta5:eta1-MeOCH(2)CH(2)C(9)H(6))(2)Yb(II)(8) and the corresponding europium(II) complexes [eta5:eta1-Me(2)Si(MeOCH(2)CH(2)C(9)H(5))(NHBu-t)](2)Eu(II)(9), (eta5:eta1-MeOCH(2)CH(2)C(9)H(5)SiMe(3))(2)Eu(II)(10) and (eta5:eta1-MeOCH(2)CH(2)C(9)H(6))(2)Eu(II)(11) in moderate to good yield. In contrast, interaction of the corresponding indene compounds 1, 2 or 3 with the lanthanide amides [(Me(3)Si)(2)N](3)Ln (Ln = Yb, Eu) was not observed, while addition of 0.5 equiv. of anhydrous LiCl to the corresponding reaction mixture produced, after workup, the corresponding ytterbium(II) or europium(II) complexes. All the new compounds were fully characterized by spectroscopic and elemental analyses. The structures of complexes, and were determined by single-crystal X-ray analyses. The catalytic activity of all the ytterbium(II) and europium(II) complexes on MMA polymerization was examined. It was found that all the ytterbium(II) and europium(II) complexes can function as single-component MMA polymerization catalysts. The temperature, solvent and ligand effects on the catalytic activity were studied.