Further Examples of the P-O-P Connection in Borophosphates: Synthesis and Characterization of Li(2) Cs(2) B(2) P(4) O(15) , LiK(2) BP(2) O(8) , and Li(3) M(2) BP(4) O(14) (M=K, Rb)

A new series of anhydrous mixed alkali-metal borophosphates-Li(2) Cs(2) B(2) P(4) O(15) (1), LiK(2) BP(2) O(8) (2), Li(3) K(2) BP(4) O(14) (3), and Li(3) Rb(2) BP(4) O(14) (4)-have been successfully synthesized by using the conventional solid-state reaction method. Compound 1 contains a novel fundamental building unit (FBU), [B(4) P(8) O(30) ], with B/P=1:2. Compound 2 contains an FBU of [B(2) P(4) O(16) ] with B/P=1:2. Compounds 3 and 4 are isotypic, and they have a [B(P(2) O(7) )(2) ] unit as their FBU. In all four compounds, their FBUs are connected through corner sharing to generate layered anionic partial structures, and then further linked with metallic polyhedra to form three-dimensional (3D) frameworks. Most interestingly, three of the four compounds contain direct P-O-P connections in their structures, which is extremely rare among borophosphates. Thermal analyses, IR spectroscopy, and UV/Vis/near-IR diffuse reflectance spectroscopy have also been performed on the four title compounds.     

The Synthesis and Structure of (1-(Diphenylphosphino)-1 - (Phenylthio)Ferrocene)Tricarbonyliron(O) (ptppf)Fe(CO)3

The complex (ptppf)Fe(CO)₃ has been prepared in high yield by the reaction of ptppf, l-(diphenyl-phosphino)-l'-(phenylthio)ferrocene, with (cis-cyclooctene)₂-Fe(CO)₃ in THF at ?60°C. The complex has been characterized by IR, ³¹P NMR, mass spectrometry and single-crystal X-ray diffraction. This compound is the first example of a ferrocenyl ligand having both sulfur and phosphorus donor atoms bound to a Fe(CO)₃ moiety. X-ray crystallography shows that the two cyclopentadienyl rings are approximately eclipsed, a rotation of 13° from exactly eclipsed conformation. The tricarbonyl iron center has a trigonal bipyramidal geometry with sulfur occupying the equatorial site and phosphorus the axial site. Crystals of (ptppf)Fe(CO)₃ are monoclinic, with a = 11.645(2), b = 14.304(1), c = 17.075(2) Å,β = 109.23(3)°, Z = 4, and space group P 2₁/n. The structure was solved according to the heavy-atom method and refined by full-matrix least-squares procedures to R = 0.037 for 2098 reflections with I ≥ 2.5σ(I).     

New layered materials: syntheses, structures, and optical properties of K(2)TiCu(2)S(4), Rb(2)TiCu(2)S(4), Rb(2)TiaAg(2)S(4), Cs(2)TiAg(2)sS(4), and Cs(2)TiCu(2)Se(4)

The new compounds K(2)TiCu(2)S(4), Rb(2)TiCu(2)S(4), Rb(2)TiAg(2)S(4), Cs(2)TiAg(2)S(4), and Cs(2)TiCu(2)Se(4) have been synthesized by the reactions of A(2)Q(3) (A = K, Rb, Cs; Q = S, Se) with Ti, M (M = Cu or Ag), and Q at 823 K. The compounds Rb(2)TiCu(2)S(4), Cs(2)TiAg(2)S(4), and Cs(2)TiCu(2)Se(4) are isostructural. They crystallize with two formula units in space group P4(2)/mcm of the tetragonal system in cells of dimensions a = 5.6046(4) A, c = 13.154(1) A for Rb(2)TiCu(2)S(4), a =6.024(1) A, c = 13.566(4) A for Cs(2)TiAg(2)S(4), and a =5.852(2) A, c =14.234(5) A for Cs(2)TiCu(2)Se(4) at 153 K. Their structure is closely related to that of Cs(2)ZrAg(2)Te(4) and comprises [TiM(2)Q(4)(2)(-)] layers, which are separated by alkali metal atoms. The [TiM(2)Q(4)(2)(-)] layer is anti-fluorite-like with both Ti and M atoms tetrahedrally coordinated to Q atoms. Tetrahedral coordination of Ti(4+) is rare in the solid state. On the basis of unit cell and space group determinations, the compounds K(2)TiCu(2)S(4) and Rb(2)TiAg(2)S(4) are isostructural with the above compounds. The band gaps of K(2)TiCu(2)S(4), Rb(2)TiCu(2)S(4), Rb(2)TiAg(2)S(4), and Cs(2)TiAg(2)S(4) are 2.04, 2.19, 2.33, and 2.44 eV, respectively, as derived from optical measurements. From band-structure calculations, the optical absorption for an A(2)TiM(2)Q(4) compound is assigned to a transition from an M d and Q p valence band (HOMO) to a Ti 3d conduction band.     

Polydentate N(2)S(2)O and N(2)S(2)O(2) Ligands as Alcoholic Derivatives of (N,N'-Bis(2-mercaptoethyl)-1,5-diazacyclooctane)nickel(II) and (N,N'-Bis(2-mercapto-2-methylpropane)-1,5-diazacyclooctane)nickel(II)

The synthesis, structural characterization, spectroscopic, and electrochemical properties of N(2)S(2)-ligated Ni(II) complexes, (N,N'-bis(2-mercaptoethyl)-1,5-diazacyclooctane)nickel(II), (bme-daco)Ni(II), and (N,N'-bis(2-mercapto-2-methylpropane)1,5-diazacyclooctane)nickel(II), (bme-daco)Ni(II), derivatized at S with alcohol-containing alkyl functionalities, are described. Reaction of (bme-daco)Ni(II) with 2-iodoethanol afforded isomers, (N,N'-bis(5-hydroxy-3-thiapentyl)-1,5-diazacyclooctane-O,N,N',S,S')halonickel(II) iodide (halo = chloro or iodo), 1, and (N,N'-bis(5-hydroxy-3-thiapentyl)-1,5-diazacyclooctane-N,N',S,S')nickel(II) iodide, 2, which differ in the utilization of binding sites in a potentially hexadentate N(2)S(2)O(2) ligand. Blue complex 1 contains nickel in an octahedral environment of N(2)S(2)OX donors; X is best modeled as Cl. It crystallizes in the monoclinic space group P2(1)/n with a = 12.580(6) ?, b = 12.291(6) ?, c = 13.090(7) ?, beta = 97.36(4) degrees, and Z = 4. In contrast, red complex 2 binds only the N(2)S(2) donor set forming a square planar nickel complex, leaving both -CH(2)CH(2)OH arms dangling; the iodide ions serve strictly as counterions. 2 crystallizes in the orthorhombic space group Pca2(1) with a = 15.822(2) ?, b = 13.171(2) ?, c = 10.0390(10) ?, and Z = 4. Reaction of (bme-daco)Ni(II) with 1,3-dibromo-2-propanol affords another octahedral Ni species with a N(2)S(2)OBr donor set, ((5-hydroxy-3,7-dithianonadiyl)-1,5-diazacyclooctane-O,N,N',S,S')bromonickel(II) bromide, 3. Complex 3 crystallizes in the orthorhombic space group Pca2(1) with a = 15.202(5) ?, b = 7.735(2) ?, c = 15.443(4) ?, and Z = 4. Complex 4.2CH(3)CN was synthesized from the reaction of (bme-daco)Ni(II) with 1,3-dibromo-2-propanol. It crystallizes in the monoclinic space group P2/c with a = 20.348(5) ?, b = 6.5120(1) ?, c = 20.548(5) ?, and Z = 4.     

OH(3) (-) and O(2)H(5) (-) double Rydberg anions: predictions and comparisons with NH(4) (-) and N(2)H(7) (-)

A low barrier in the reaction pathway between the double Rydberg isomer of OH(3) (-) and a hydride-water complex indicates that the former species is more difficult to isolate and characterize through anion photoelectron spectroscopy than the well known double Rydberg anion (DRA), tetrahedral NH(4) (-). Electron propagator calculations of vertical electron detachment energies (VEDEs) and isosurface plots of the electron localization function disclose that the transition state's electronic structure more closely resembles that of the DRA than that of the hydride-water complex. Possible stabilization of the OH(3) (-) DRA through hydrogen bonding or ion-dipole interactions is examined through calculations on O(2)H(5) (-) species. Three O(2)H(5) (-) minima with H(-)(H(2)O)(2), hydrogen-bridged, and DRA-molecule structures resemble previously discovered N(2)H(7) (-) species and have well separated VEDEs that may be observable in anion photoelectron spectra.     

Bis(trifluoroacetyl) peroxide, CF(3)C(O)OOC(O)CF(3)

Pure, highly explosive CF(3)C(O)OOC(O)CF(3) is prepared for the first time by low-temperature reaction between CF(3)C(O)Cl and Na(2)O(2). At room temperature CF(3)C(O)OOC(O)CF(3) is stable for days in the liquid or gaseous state. The melting point is -37.5 degrees C, and the boiling point is extrapolated to 44 degrees C from the vapor pressure curve log p = -1875/T + 8.92 (p/mbar, T/K). Above room temperature the first-order unimolecular decay into C(2)F(6) + CO(2) occurs with an activation energy of 129 kJ mol(-1). CF(3)C(O)OOC(O)CF(3) is a clean source for CF(3) radicals as demonstrated by matrix-isolation experiments. The pure compound is characterized by NMR, vibrational, and UV spectroscopy. The geometric structure is determined by gas electron diffraction and quantum chemical calculations (HF, B3PW91, B3LYP, and MP2 with 6-31G basis sets). The molecule possesses syn-syn conformation (both C=O bonds synperiplanar to the O-O bond) with O-O = 1.426(10) A and dihedral angle phi(C-O-O-C) = 86.5(32) degrees. The density functional calculations reproduce the experimental structure very well.     

Novel quaternary lanthanum bismuth sulfides Pb(2)La(x)Bi(8-x)(S(14)), Sr(2)La(x)Bi(8-x)S(14), and Cs(2)La(x)Bi(10-x)S(16) with complex structures

The compounds Pb(2)La(x)Bi(8-x)S(14) (I), Sr(2)La(x)Bi(8-x)S(14) (II), and Cs(2)La(x)Bi(10-x)S(16) (III) were synthesized from the corresponding elements or binary sulfides at temperatures above 850 degrees C. Compounds I and II are isostructural, forming a new structure type, while the structure of III is related to the structure of the mineral kobellite. All compounds crystallize in the orthorhombic space group Pnma (No. 62) with a = 21.2592(4) A, b = 4.0418(1) A, c = 28.1718(3) A, Z = 4 for I, a = 21.190(1) A, b = 4.0417(2) A, c = 28.285(2) A, Z = 4 for II and a = 34.893(4) A, b = 4.0697(4) A, c = 21.508(2) A, Z = 4 for III. All compounds exhibit mixed site occupancy between Bi and La. Furthermore, I and II exhibit disorder between the divalent atom (Sr or Pb) and/or La and/or Bi. The structures of I and II consist of thin walls made of two metal-atom-thick NaCl-type blocks running in two opposite directions in the ac plane, forming rhombus-shaped tunnels. These tunnels are filled with Bi(2)Te(3)-type fragments. In the points where the walls intersect they form Gd(2)S(3)-type fragments. The structure of III consists of a complex three-dimensional framework with Cs-filled tunnels. All compounds are semiconductors with band gaps around 1.0 eV, and they melt around 740-860 degrees C.     

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'.     

{H(3-(t)Bupz)B(3-(t)Bupz)(2)-eta(2)}AlEt(2) and {H(3-(t)Bupz)B(3-(t)Bupz)(5-(t)Bupz)-eta(2)}AlEt(2). Structure, Dynamic Solution Behavior, and the 1,2-Borotropic Shift

HB(3-(t)Bupz)(3)Tl and AlEt(3) in benzene yield {H(3-(t)Bupz)B(3-(t)Bupz)(2)-eta(2)}AlEt(2), 1, as a hydrocarbon-soluble crystalline solid. Compound 1 is also obtained in a related reaction involving ClAlEt(2) via a preferential metathesis of the Al-Cl bond. Crystal data for 1 at -101 degrees C: a = 11.770(3) ?, b = 11.054(3) ?, c = 21.973(6) ?, beta = 95.57(1) degrees, Z = 4, space group P2(1)/a. In 1 the Al center is four-coordinate with Al-C = 1.97(1) ? and Al-N = 1.99(1) ? and with C-Al-C = 127 degrees and N-Al-N = 101 degrees being the largest and smallest angles, respectively. The average N-B-N angle is 109(1) degrees. In toluene-d(8) and tetrahydrofuran-d(8), 1 shows two types of 3-(t)Bupz groups in the integral ratio 2:1 and two distinct ethyl ligands. At low temperature there is a broadening of the 3-(t)Bupz singlet that is assigned to the eta(2)-(t)Bupz ligands. Up to +60 degrees C, compound 1 is nonfluxional on the NMR time scale but does isomerize to {H(3-(t)Bupz)B(3-(t)Bupz)(5-(t)Bupz)-eta(2)}AlEt(2), 2. Crystal data for 2 at -172 degrees C: a = 29.235(5) ?, b = 11.298(1) ?, c = 22.033(3) ?, beta = 129.66(1) degrees, Z = 8, space group = C2/c. In 2 there is a pseudotetrahedral Al center with Al-C = 1.97(1) ? (average) and Al-N = 1.95(1) ? (average) and with C-Al-C = 119 degrees and N-Al-N = 98 degrees as the largest and smallest angles, respectively. The average N-B-N angle is 108(1) degrees. In 2 the eta(2)-tris(alkylpyrazolyl)borate ligand isomerizes by a 1,2-borotropic shift to give one 5-(t)Bupz fragment that is part of the eta(2)-N,N' aluminum-bonded ligand. Variable-temperature (1)H NMR spectra of 2 in toluene-d(8) and THF-d(8) reveal temperature-dependent exchange involving the 3-(t)Bupz moieties, with more rapid site exchange in toluene-d(8) than in THF-d(8). At low temperature there are two ethyl signals, one of which indicates diastereotopic methylene protons, as well as three (t)Bu signals in the ratio 1:1:1. The dynamic behavior of 2 is consistent with an eta(2) right harpoon over left harpoon eta(3) exchange process as opposed to an eta(2) right harpoon over left harpoon eta(1) exchange wherein the Al center is transiently three-coordinate. The isomerization of 1 to 2 has been studied in benzene-d(6) (DeltaH() = 21.0(2) kcal/mol, DeltaS() = -15(1) eu) and THF-d(8) (DeltaH() = 18.3(4) kcal/mol, DeltaS() = -15(1) eu) and compared to a related isomerization involving {H(2)B(3-(t)Bupz)(2)-eta(2)}AlMe(2) reported by Parkin and Looney [Polyhedron 1990, 9, 265] in benzene-d(6) (DeltaH() = 34.5(8) kcal/mol, DeltaS() = 6(2) eu). It is proposed that the rate-determining 1,2-borotropic shift in the 1 --> 2 reaction occurs in a noncoordinating (t)Bupz group and that this is followed by a rapid associative interchange of pz groups wherein the sterically less demanding 5-(t)Bupz moiety remains bound to the metal.     

Proposed fluorination mechanism of CB(5)H(6)(-) and CB(9)H(10)(-) with HF. Evidence of kinetic control in the formation of 2-CB(5)H(5)F(-) and 6-CB(9)H(9)F(-)

Two pathways have been considered in the fluorination of CB(5)H(6)(-) and CB(9)H(10)(-) by HF. In the ionic HF fluorination pathway, the monocarborane anion cage is first protonated in a BBB face followed by H(2) elimination and fluoride anion addition. In the covalent HF fluorination pathway, HF is first coordinated through hydrogen to the BBB face. Next, the fluorine can add to either an axial or equatorial boron atom which opens the cage to a nido structure with an endo fluoride substituent. Endo to exo rearrangement occurs with a small activation barrier followed by H(2) elimination. In both pathways, fluorination at the equatorial boron position is predicted to have smaller activation barriers even though substitution at the axial position leads to the more stable products.     

Silver(I) undecafluorodiantimonate(V)

The reaction between AgBF4 and excess of SbF5 in anhydrous hydrogen fluoride (aHF) yields the white solid AgSb2F11 after the solvent and the excess of SbF5 have been pumped off. Reaction between equimolar amounts of AgSb2F11 and AgBF4 yields AgSbF6. Meanwhile, oxidation of solvolyzed AgSb2F11 in aHF by elemental fluorine yields a clear blue solution of solvated Ag(II) cations and SbF6- anions. AgSb2F11 is orthorhombic, at 250 K, Pbca, with a=1091.80(7) pm, b=1246.28(8) pm, c=3880.2(3) pm, V=5.2797(6) nm3, and Z=24. The crystal structure of AgSb2F11 is related to the already known crystal structure of H3OSb2F11. Vibrational spectra of AgSb2F11 entirely match the literature-reported vibrational spectra of beta-Ag(SbF6)2, for which a formulation of a mixed-valence AgI/AgIII compound was suggested (AgIAgIII(SbF6)4). On the basis of obtained results it can be concluded that previously reported beta-Ag(SbF6)2 is in fact Ag(I) compound with composition AgSb2F11.     

Oxidation chemistry of poly(ethylene glycol)-supported carbonylruthenium(II) and dioxoruthenium(VI) meso-tetrakis(pentafluorophenyl)porphyrin

[Ru(II)(F(20)-tpp)(CO)] (1, F(20)-tpp=meso-tetrakis(pentafluorophenyl)porphyrinato dianion) was covalently attached to poly(ethylene glycol) (PEG) through the reaction of 1 with PEG and sodium hydride in DMF. The water-soluble PEG-supported ruthenium porphyrin (PEG-1) is an efficient catalyst for 2,6-Cl(2)pyNO oxidation and PhI==NTs aziridination/amidation of hydrocarbons, and intramolecular amidation of sulfamate esters with PhI(OAc)(2). Oxidation of PEG-1 by m-CPBA in CH(2)Cl(2), dioxane, or water afforded a water-soluble PEG-supported dioxoruthenium(VI) porphyrin (PEG-2), which could react with hydrocarbons to give oxidation products in up to 80 % yield. The behavior of the two PEG-supported ruthenium porphyrin complexes in water was probed by NMR spectroscopy and dynamic light-scattering measurements. PEG-2 is remarkably stable to water. The second-order rate constants (k(2)) for the oxidation of styrene and ethylbenzene by PEG-2 in dioxane-water increase with water content, and the k(2) values at a water content of 70 % or 80 % are up to 188 times that obtained in ClCH(2)CH(2)Cl.     

Syntheses and structures of the infinite chain compounds Cs(4)Ti(3)Se(13), Rb(4)Ti(3)S(14), Cs(4)Ti(3)S(14), Rb(4)Hf(3)S(14), Rb(4)Zr(3)Se(14), Cs(4)Zr(3)Se(14), and Cs(4)Hf(3)Se(14)

The alkali metal/group 4 metal/polychalcogenides Cs(4)Ti(3)Se(13), Rb(4)Ti(3)S(14), Cs(4)Ti(3)S(14), Rb(4)Hf(3)S(14), Rb(4)Zr(3)Se(14), Cs(4)Zr(3)Se(14), and Cs(4)Hf(3)Se(14) have been synthesized by means of the reactive flux method at 823 or 873 K. Cs(4)Ti(3)Se(13) crystallizes in a new structure type in space group C(2)(2)-P2(1) with eight formula units in a monoclinic cell at T = 153 K of dimensions a = 10.2524(6) A, b = 32.468(2) A, c = 14.6747(8) A, beta = 100.008(1) degrees. Cs(4)Ti(3)Se(13) is composed of four independent one-dimensional [Ti(3)Se(13)(4-)] chains separated by Cs(+) cations. These chains adopt hexagonal closest packing along the [100] direction. The [Ti(3)Se(13)(4-)] chains are built from the face- and edge-sharing of pentagonal pyramids and pentagonal bipyramids. Formal oxidation states cannot be assigned in Cs(4)Ti(3)Se(13). The compounds Rb(4)Ti(3)S(14), Cs(4)Ti(3)S(14), Rb(4)Hf(3)S(14), Rb(4)Zr(3)Se(14), Cs(4)Zr(3)Se(14), and Cs(4)Hf(3)Se(14) crystallize in the K(4)Ti(3)S(14) structure type with four formula units in space group C(2)(h)()(6)-C2/c of the monoclinic system at T = 153 K in cells of dimensions a = 21.085(1) A, b = 8.1169(5) A, c = 13.1992(8) A, beta = 112.835(1) degrees for Rb(4)Ti(3)S(14);a = 21.329(3) A, b = 8.415(1) A, c = 13.678(2) A, beta = 113.801(2) degrees for Cs(4)Ti(3)S(14); a = 21.643(2) A, b = 8.1848(8) A, c = 13.331(1) A, beta = 111.762(2) degrees for Rb(4)Hf(3)S(14); a = 22.605(7) A, b = 8.552(3) A, c = 13.880(4) A, beta = 110.919(9) degrees for Rb(4)Zr(3)Se(14); a = 22.826(5) A, b = 8.841(2) A, c = 14.278(3) A, beta = 111.456(4) degrees for Cs(4)Zr(3)Se(14); and a = 22.758(5) A, b = 8.844(2) A, c = 14.276(3) A, beta = 111.88(3) degrees for Cs(4)Hf(3)Se(14). These A(4)M(3)Q(14) compounds (A = alkali metal; M = group 4 metal; Q = chalcogen) contain hexagonally closest-packed [M(3)Q(14)(4-)] chains that run in the [101] direction and are separated by A(+) cations. Each [M(3)Q(14)(4-)] chain is built from a [M(3)Q(14)] unit that consists of two MQ(7) pentagonal bipyramids or one distorted MQ(8) bicapped octahedron bonded together by edge- or face-sharing. Each [M(3)Q(14)] unit contains six Q(2)(2-) dimers, with Q-Q distances in the normal single-bond range 2.0616(9)-2.095(2) A for S-S and 2.367(1)-2.391(2) A for Se-Se. The A(4)M(3)Q(14) compounds can be formulated as (A(+))(4)(M(4+))(3)(Q(2)(2-))(6)(Q(2-))(2).     

Phosphine-boranes as bidentate ligands: formation of [8,8-eta(2)-(eta(2)-(BH(3)).dppm)-nido-8,7-RhSB(9)H(10)] and [9,9-eta(2)-(eta(2)-(BH(3)).dppm)-nido-9,7,8-RhC(2)B(8)H(11)] from [8,8-(eta(2)-dppm)-8-(eta(1)-dppm)-nido-8,7-RhSB(9)H(10)] and [9,9-(eta(2)-dppm)-9-(eta(1)-dppm)-nido-9,7,8-RhC(2)B(8)H(11)], respectively

The two clusters [8,8-(eta(2)-dppm)-8-(eta(1)-dppm)-nido-8,7-RhSB(9)H(10)] (1) and [9,9-(eta(2)-dppm)-9-(eta(1)-dppm)-nido-9,7,8-RhC(2)B(8)H(11)] (2) (dppm = PPh(2)CH(2)PPh(2)), both of which contain pendant PPh(2) groups, react with BH(3).thf to afford the species [8,8-eta(2)-(eta(2)-(BH(3)).dppm)-nido-8,7-RhSB(9)H(10)] (3) and [9,9-eta(2)-(eta(2)-(BH(3)).dppm))-nido-9,7,8-RhC(2)B(8)H(11)] (4), respectively. These two species are very similar in that they both contain the bidentate ligand [(BH(3)).dppm], which coordinates to the Rh center via a PPh(2) group and also via a eta(2)-BH(3) group. Thus, the B atom in the BH(3) group is four-coordinate, bonded to Rh by two bridging hydrogen atoms, to a terminal H atom, and to a PPh(2) group. At room temperature, the BH(3) group is fluxional; the two bridging H atoms and the terminal H atom are equivalent on the NMR time scale. The motion is arrested at low temperature with DeltaG++ = ca. 37 and 42 kJ mol(-1), respectively, for 3 and 4. Both species are characterized completely by NMR and mass spectral measurements as well as by elemental analysis and single-crystal structure determinations.     

Acidites et complexes des acides (alkyl-et aminoalkyl-) phosphoniques-IV: acides aminoalkylphosphoniques R(1)R(2)N(CH(2))(n)CR(3)R(4)PO(3)H(2)

The acids under study differed from one another in length of the carbon chain [N + H(3)(CH(2))(n)PO(3)H(-) for n = 1, 2, 3], substitution on the nitrogen atom [R(1)R(2)N + HCH(2)PO(3)H(-) for R(1) = H; R(2) = Me, Et and R(1) = R(2)= Me, Et] or extent of branching on the carbon atom adjacent to functional groups [N + H(3)CR(3)R(4)PO(3)H(-) for R(3) = H; R(4) = Me, Et, nPr, iPr, nBu and R(3) = R(4) = Me]. Acidity constants and overall stability constants of complexes formed with Ca(II), Mg(II), Co(II), Ni(II), Cu(II), Zn(II) were obtained with the multiparametric refinement programs MUPROT and MUCOMP, applied to potentiometric data, obtained at 25 degrees , in a 0.1M potassium nitrate medium. In the most general case, the existing species are MHA(+), MA, M(OH)A(-), MH(2)A(2), MHA(-)(2) and MA(2-)(2), where A(2-) stands for the fully ionized ligand; preliminary examination of results points out some predominant microscopic forms.     

Promoting Li(2)O(2) oxidation by an La(1.7)Ca(0.3)Ni(0.75)Cu(0.25)O(4) layered perovskite in lithium-oxygen batteries

We demonstrate for the first time that La(1.7)Ca(0.3)Ni(0.75)Cu(0.25)O(4) with a layered perovskite structure promotes electrochemical oxidation of Li(2)O(2) in lithium-oxygen batteries with a non-aqueous aprotic electrolyte.     

Reaction of (R)-(-)-2-aminomethylpyrrolidine(1,1-cyclobutanedicarboxylato)platinum( II) with guanosine

The reaction of a new antitumor platinum complex, (R)-(-)-2-aminomethylpyrrolidine(1,1-cyclobutanedicarboxylato++ +)platinum(II) (1) with guanosine at room temperature in an aqueous solution was followed by proton nuclear magnetic resonance (1H-NMR) spectroscopy and high performance liquid chromatography (HPLC) at intervals. Both techniques showed that a new compound was formed by displacement of the 1,1-cyclobutanedicarboxylate moiety of 1 with two guanosines, and its 1H-NMR spectrum and HPLC chromatogram were proved to be identical with those of [(R)-(-)-2-aminomethylpyrrolidine]bis(N7-guanosine)platinum(II) (2), which was obtained upon successive treatment of (R)-(-)-2-aminomethylpyrrolidinedichloroplatinum(II) (3) with AgNO3 and 2 mol eq of guanosine in water. The binding sites of the platinum to the two guanosine moieties in 2 were confirmed by the pH dependence of the two G-H8 signals.     

Fluorescence excitation spectra of the b (1)Pi(u), b(') (1)Sigma(u) (+), c(n) (1)Pi(u), and c(n) (') (1)Sigma(u) (+) states of N(2) in the 80-100 nm region

Fluorescence excitation spectra produced through photoexcitation of N(2) using synchrotron radiation in the spectral region between 80 and 100 nm have been studied. Two broadband detectors were employed to simultaneously monitor fluorescence in the 115-320 nm and 300-700 nm regions, respectively. The peaks in the vacuum ultraviolet fluorescence excitation spectra are found to correspond to excitation of absorption transitions from the ground electronic state to the b (1)Pi(u), b(') (1)Sigma(u) (+), c(n) (1)Pi(u) (with n=4-8), c(n) (') (1)Sigma(u) (+) (with n=5-9), and c(4) (')(v('))(1)Sigma(u) (+) (with v(')=0-8) states of N(2). The relative fluorescence production cross sections for the observed peaks are determined. No fluorescence has been produced through excitation of the most dominating absorption features of the b-X transition except for the (1,0), (5,0), (6,0), and (7,0) bands, in excellent agreement with recent lifetime measurements and theoretical calculations. Fluorescence peaks, which correlate with the long vibrational progressions of the c(4) (') (1)Sigma(u) (+) (with v(')=0-8) and the b(') (1)Sigma(u) (+) (with v(') up to 19), have been observed. The present results provide important information for further unraveling of complicated and intriguing interactions among the excited electronic states of N(2). Furthermore, solar photon excitation of N(2) leading to the production of c(4) (')(0) may provide useful data required for evaluating and analyzing dayglow models relevant to the interpretation of c(4) (')(0) in the atmospheres of Earth, Jupiter, Saturn, Titan, and Triton.     

Photoelectron spectroscopy and density functional theory study of TiAlO(y) (-) (y=1-3) and TiAl(2)O(y) (-) (y=2-3) clusters

Small titanium-aluminum oxide clusters, TiAlO(y) (-) (y=1-3) and TiAl(2)O(y) (-) (y=2-3), were studied by using anion photoelectron spectroscopy. The adiabatic detachment energies of TiAlO(y) (-) (y=1-3) were estimated to be 1.11±0.05, 1.70±0.08, and 2.47±0.08eV based on their photoelectron spectra; those of TiAl(2)O(2) (-) and TiAl(2)O(3) (-) were estimated to be 1.17±0.08 and 2.2±0.1eV, respectively. The structures of these clusters were determined by comparison of density functional calculations with the experimental results. The structure of TiAlO(-) is nearly linear with the O atom in the middle. That of TiAlO(2) (-) is a kite-shaped structure. TiAlO(3) (-) has a kite-shaped TiAlO(2) unit with the third O atom attaching to the Ti atom. TiAl(2)O(2) (-) has two nearly degenerate Al-O-Ti-O-Al chain structures that can be considered as cis and trans forms. TiAl(2)O(3) (-) has two low-lying isomers, kite structure and book structure. The structures of these clusters indicate that the Ti atom tends to bind to more O atoms.     

Supramolecular networks of silver(I) and iron(II) complexes of the third generation tris(pyrazolyl)methane ligand Ph(2)(O)POCH(2)C(pz)(3) (pz = pyrazolyl ring)

The new ligand Ph(2)(O)POCH(2)C(pz)(3) (pz = pyrazolyl ring), prepared from the reaction of HOCH(2)C(pz)(3) and Ph(2)P(O)Cl in the presence of base, reacts with either AgBF(4) or Fe(BF(4))(2).6H(2)O in a 2/1 molar ratio to yield {[Ph(2)(O)POCH(2)C(pz)(3)](2)Ag}(BF(4)) () and {[Ph(2)(O)POCH(2)C(pz)(3)](2)Fe}(BF(4))(2) (), respectively. In the structure of , the silver is in an unusual planar geometry with each of the ligands in a kappa(2)-kappa(0) coordination mode. Slow evaporation of a thf solution of yields crystalline [Ph(2)(O)POCH(2)C(pz)(3)Ag](2)(thf)(2)}(BF(4))(2) (). In each cationic unit of , the two Ph(2)(O)POCH(2)C(pz)(3) ligands coordinate to the same two silver(i) centers in a kappa(2)-kappa(1) bonding mode, with a silver atom separation of 3.36 A. The supramolecular structure of both and is dominated by a pair of cooperative hydrogen bonding interactions between the Ph(2)P(O) secondary tecton and a hydrogen atom from a methylene group situated on a neighboring building block, which arranges the cations in chains. The reaction of HC(pz)(3) and AgO(3)SCF(3) (AgOTf) yields {[HC(pz)(3)](2)Ag(2)}(OTf)(2) (). The cationic unit in has a structure very similar to that of , but with a much shorter distance between the silver atoms at 2.86 A. The supramolecular structure of is dominated by an unusual pyrazolyl embrace interaction where the acceptor ring in the C-Hpi interaction is the pyrazolyl ring kappa(1)-bonded to silver in the adjacent dimeric unit rather than the other ring in a kappa(2)-bonded Cpz(2) unit. This interaction arranges the cations in chains which are further organized into sheets by the triflate anions that link the chains via combined AgO/CHO interactions. The iron in is octahedral with each tris(pyrazolyl)methane unit in the kappa(3)-tripodal coordination mode. The supramolecular structure is sheets formed by hydrogen bonding between the Ph(2)P(O) oxygen and a meta-position hydrogen on one of the diphenylphosphine rings from an adjacent cation.