Intramolecularly coordinated telluroxane clusters and polymers

The stoichiometrically controlled chlorination of the diarylditelluride (8-Me(2) NC(10) H(6) Te)(2) with SO(2) Cl(2) afforded the aryltellurinyl chloride 8-Me(2) NC(10) H(6) TeCl (1) and the aryltellurium trichloride 8-Me(2) NC(10) H(6) TeCl(3) (2). Alternatively, 1 was obtained by the reaction of the aryltellurenyl diethyldithiacarbamate 8-Me(2) NC(10) H(6) Te(S(2) CNEt(2) ) with hydrochloric acid. The base hydrolysis of 2 provided the novel telluroxanes (8-Me(2) NC(10) H(6) Te)(2) OCl(4) (3), (8-Me(2) NC(10) H(6) Te)(6) O(5) Cl(8) (4), (8-Me(2) NC(10) H(6) Te)(6) O(8) Cl(2) (5), [(8-Me(2) NC(10) H(6) Te)(2) O(3) ](n) (6) and (8-Me(2) NC(10) H(6) Te)(6) O(8) (OH)(2) (7) depending on the reaction conditions applied. The reaction of 7 with ClTe(OiPr)(3) in the presence of water gave rise to the telluroxane (8-Me(2) NC(10) H(6) Te)(6) Te(2) O(12) Cl(2) (8). The crystal and molecular structures of 1-3 and 5-8 were determined by X-ray crystallography. The telluroxane clusters and polymers 6-8 hold potential as model compounds for alkali tellurite glasses (M(2) O)(x) (TeO(2) )(1-x) (M=Li, Na, K) for which no precise structural data are available.     

Au nanoparticles stabilised by PEGylated low generation PAMAM dendrimers: design, characterisation and properties

The preparation and characterisation of a series of well-defined low generation (poly)amidoamine (PAMAM)-based dendrimers with end-grafted ethylene glycol ether moieties of type N(CH(2)CH(2)C(O)NHCH(2)CH(2)NR(2))(3) (3a, R=CH(2)CH(2)C(O)OCH(2)CH(2)OCH(3); 3b, R=CH(2)CH(2)C(O)O(CH(2)CH(2)O)(2)C(2)H(5); 3c, R=CH(2)CH(2)C(O)O(CH(2)CH(2)O)(9)CH(3)), [CH(2)N(CH(2)CH(2)C(O)NHCH(2)CH(2)NR(2))(2)](2) (4, R=CH(2)CH(2)C(O)O(CH(2)CH(2)O)(2)C(2)H(5)) and (R(2)NCH(2)CH(2)NHC(O)CH(2)CH(2))N[CH(2)CH(2)N(CH(2)CH(2)C(O)NHCH(2)CH(2)NR(2))(2)](2) (5a, R=CH(2)CH(2)C(O)OCH(2)CH(2)OCH(3); 5b, R=CH(2)CH(2)C(O)O(CH(2)CH(2)O)(2)C(2)H(5); 5c, R=CH(2)CH(2)C(O)O(CH(2)CH(2)O)(9)CH(3)) and their application for the stabilisation of gold nanoparticles (Au NPs) is described. These dendrimers were prepared by a consecutive divergent synthesis methodology including Michael addition and amidation cycles. For comparison, amidoamine related model compounds N(C(3)H(7))R(2) (1, R=CH(2)CH(2)C(O)O(CH(2)CH(2)O)(2)C(2)H(5)) and [CH(2)NR(2)](2) (2, R=CH(2)CH(2)C(O)O(CH(2)CH(2)O)(2)C(2)H(5)) were also synthesised to estimate the minimum required donating capabilities of the stabiliser. Loading the appropriate dendritic templates with H[AuCl(4)] (12) and subsequent reduction of the respective metallodendrimers with Na[BH(4)] produced dendrimer encapsulated gold colloids. The dendrimeric scaffold, the length of the ethylene glycols, the adjusted stabilizer:gold ratio and the duration of reaction time affects the average Au particle diameter in a range of 4.0 (±0.9) to 58.5 (±14.5) nm. Furthermore, depending on the nature of the stabiliser, nanoparticles were formed having spherical or multiple morphologies. Characterisation by transmission electron microscopy (TEM), dynamic light scattering (DLS), UV/vis, and IR spectroscopy revealed that Au NPs are formed and protected inside the dendrimer scaffold.     

Reactivity studies of oxo-Mo(IV) complexes containing potential hydrogen-bond acceptor/donor phenolate ligands

Reactivity studies of oxo-Mo(IV) complexes, Tp(iPr)MoO{2-OC(6)H(4)C(O)R-κ(2)O,O'} (R = Me, Et, OMe, OEt, OPh, NHPh), containing chelated hydrogen-bond donor/acceptor phenolate ligands are reported. Hydrolysis/oxidation of Tp(iPr)MoO(2-OC(6)H(4)CO(2)Ph-κ(2)O,O') in the presence of methanol yields tetranuclear [Tp(iPr)MoO(μ-O)(2)MoO](2)(μ-OMe)(2) (1), while condensation of Tp(iPr)MoO{2-OC(6)H(4)C(O)Me-κ(2)O,O'} and methylamine gives the chelated iminophenolate complex, Tp(iPr)MoO{2-OC(6)H(4)C(Me)NMe-κ(2)O,N} (2), rather than the aqua complex, Tp(iPr)MoO{2-OC(6)H(4)C(Me)NMe-κO}(OH(2)). The oxo-Mo(IV) complexes are readily oxidized by dioxygen or hydrogen peroxide to the corresponding cis-dioxo-Mo(VI) complexes, Tp(iPr)MoO(2){2-OC(6)H(4)C(O)R}; in addition, suitable one-electron oxidants, e.g., [FeCp(2)]BF(4) and [N(C(6)H(4)Br)(3)][SbCl(6)], oxidize the complexes to their EPR-active (g(iso) ≈ 1.942) molybdenyl counterparts (3, 4). Molybdenyl complexes such as Tp(iPr)MoOCl{2-OC(6)H(4)C(O)R} (5) and Tp(iPr)MoOCl(2) also form when the complexes react with chlorinated solvents. The ester derivatives (R = OMe, OEt, OPh) react with propylene sulfide to form cis-oxosulfido-Mo(VI) complexes, Tp(iPr)MoOS{2-OC(6)H(4)C(O)R}, that crystallize as dimeric μ-disulfido-Mo(V) species, [Tp(iPr)MoO{2-OC(6)H(4)C(O)R}](2)(μ-S(2)) (6-8). The crystal structures of [Tp(iPr)MoO(μ-O)(2)MoO](2)(μ-OMe)(2), Tp(iPr)MoO{2-OC(6)H(4)C(Me)NMe}, Tp(iPr)MoOCl{2-OC(6)H(4)C(O)NHPh}·{2-HOC(6)H(4)C(O)NHPh}, and [Tp(iPr)MoO{2-OC(6)H(4)C(O)R}](2)(μ-S(2)) (R = OMe, OEt) are reported.     

Insertion, isomerization, and cascade reactivity of the tethered silylalkyl uranium metallocene (η(5)-C5Me4SiMe2CH2-κC)2U

Investigation of the insertion reactivity of the tethered silylalkyl complex (η(5)-C(5)Me(4)SiMe(2)CH(2)-κC)(2)U (1) has led to a series of new reactions for U-C bonds. Elemental sulfur reacts with 1 by inserting two sulfur atoms into each of the U-C bonds to form the bis(tethered alkyl disulfide) complex (η(5):η(2)-C(5)Me(4)SiMe(2)CH(2)S(2))(2)U (2). The bulky substrate N,N'-diisopropylcarbodiimide, (i)PrN═C═N(i)Pr, inserts into only one of the U-C bonds of 1 to produce the mixed-tether complex (η(5)-C(5)Me(4)SiMe(2)CH(2)-κC)U[η(5)-C(5)Me(4)SiMe(2)CH(2)C((i)PrN)(2)-κ(2)N,N'] (3). Carbon monoxide did not exclusively undergo a simple insertion into the U-C bond of 3 but instead formed {μ-[η(5)-C(5)Me(4)SiMe(2)CH(2)C(═N(i)Pr)O-κ(2)O,N]U[OC(C(5)Me(4)SiMe(2)CH(2))CN((i)Pr)-κ(2)O,N](2) (4) in a cascade of reactions that formally includes U-C bond cleavage, C-N bond cleavage of the amidinate ligand, alkyl or silyl migration, U-O, C-C, and C-N bond formations, and CO insertion. The reaction of 3 with isoelectronic tert-butyl isocyanide led to insertion of the substrate into the U-C bond, but with a rearrangement of the amidinate ligand binding mode from κ(2) to κ(1) to form [η(5):η(2)-C(5)Me(4)SiMe(2)CH(2)C(═N(t)Bu)]U[η(5)-C(5)Me(4)SiMe(2)CH(2)C(═N(i)Pr)N((i)Pr)-κN] (5). The product of double insertion of (t)BuN≡C into the U-C bonds of 1, namely [η(5):η(2)-C(5)Me(4)SiMe(2)CH(2)C(═N(t)Bu)](2)U (6), was found to undergo an unusual thermal rearrangement that formally involves C-H bond activation, C-C bond cleavage, and C-C bond coupling to form the first formimidoyl actinide complex, [η(5):η(5):η(3)-(t)BuNC(CH(2)SiMe(2)C(5)Me(4))(CHSiMe(2)C(5)Me(4))]U(η(2)-HC═N(t)Bu) (7).     

Synthesis, structures of (aminopyridine)nickel complexes and their use for catalytic ethylene polymerization

A series of α-aminopyridines in the form of (2,6-C(6)H(3)N)(R(1))(CHR(2)NR(3)R(4)) (R(1) = R(2) = H R(3) = H R(4) = (i)Pr (L1a), R(4) = (t)Bu (L1b), R(4) = Ph (L1c), R(4) = 2,6-Me(2)C(6)H(3) (L1d), R(4) = 2,6-(i)Pr(2)C(6)H(3) (L1e), R(1) = R(2) = H R(3) = R(4) = Et (L1f), R(1) = H R(2) = Me R(3) = H R(4) = (i)Pr (L2a), R(4) = Ph (L2c), R(4) = 2,6-Me(2)C(6)H(3) (L2d), R(4) = 2,6-(i)Pr(2)C(6)H(3) (L2e), R(1) = Me R(2) = H R(3) = H R(4) = 2,6-(i)Pr(2)C(6)H(3) (L3e)) and β-aminopyridines in the form of (2-C(6)H(4)N)(CH(2)CH(2)NR(1)R(2)) (R(1) = H R(2) = (i)Pr (4a), R(2) = (t)Bu (L4b), R(1) = R(2) = Et (L4f)) have been prepared. Their corresponding halonickel complexes 1a-4f are synthesized by ligand substitution from (DME)NiBr(2) and the molecular structures are characterized. Four types of coordination modes include four-coordinate mononuclear species with one ligand, five-coordinate mononuclear species with two ligands, five-coordinate dinuclear species with two ligands, and a six-coordinate polymeric framework were determined by X-ray crystallography. Using methylaluminoxanes (MAO) as the activator, the nickel complexes can catalyze ethylene polymerization under moderate pressure and ambient temperature. The activity reaches 10(5) g PE mol(-1) Ni h. The PE products with high branching and high crystallinity have M(n) ~ 10(3) with PDI < 2.     

Biphenylamide ligand complexes of Li and Al: hemilabile arene donors?

Biphenylamide ligands were employed to prepare a series of Li and Al derivatives in which the ligand binds through N. Such species include: (2-C(6)H(4)Ph)Bu(t)NLi (), (2-C(6)H(4)Ph)Bu(t)NLi(THF)(2) (), (2-C(6)H(4)Ph)Bu(t)NLi.OEt(2) (), [(mu-(2-C(6)H(4)Ph)(2)N)Li](2) (), (2-C(6)H(4)Ph)(2)NLi(THF)(2) (), (2-C(6)H(4)Ph)(2)NLi.OEt(2) () amd (2-C(6)H(4)Ph)(2)NAlX(2) (X = Cl (), Me (), Et ()). Structural and spectroscopic data show that these species exhibit weak arene to metal donation. This donor is hemilabile being readily displaced by other stronger donors to give such species as (2-C(6)H(4)Ph)(2)NAlMe(2)(THF) () and (2-C(6)H(4)Ph)(2)NAlMe(2)(CH(2)PPh(3)) (). Reactions of with B(C(6)F(5))(3) results in methyl for C(6)F(5) exchange and isolation of (2-C(6)H(4)Ph)(2)NAl(C(6)F(5))(2) (). The presence the electron withdrawing groups in further strengthens the hemilabile interaction.     

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.     

Insertion of Fluoroalkenes into Activated C-H Bonds for the Preparation of Polyfluorinated Sulfanes, Alcohols, and Acyclic and Cyclic Ethers

Free radical addition reactions of tetrahydrothiophene, pentamethylene sulfide, and 1,4-thioxane with various cyclic and acyclic per- and polyfluorinated olefins are readily initiated by di-tert-butyl peroxide, providing a convenient route for synthesizing cyclic sulfanes with fluorinated side groups. Tetrahydrothiophene reacts with hexafluoropropene, perfluoroallylbenzene, perfluorocyclobutene, and 1,2-dichlorotetrafluorocyclobutene in the presence of catalytic amounts of the peroxide to give the corresponding addition products CH(2)CH(2)CH(2)SCHCF(2)CHFCF(3) (1), CH(2)CH(2)CH(2)SCHCF(2)CHFCF(2)C(6)F(5) (2), CH(2)CH(2)CH(2)SCHCFCHFCF(2)CF(2) (3), and CH(2)CH(2)CH(2)SCHCClCHClCF(2)CF(2) (4), respectively. Pentamethylene sulfide reacts analogously with hexafluoropropene to give CH(2)CH(2)CH(2)CH(2)SCHCF(2)CHFCF(3) (8). Reaction of 1,4-thioxane with hexafluoropropene or perfluoroallylbenzene gives a mixture of two products, OCH(2)CH(2)SCH(2)CHCF(2)CHFCF(3) (9) and SCH(2)CH(2)OCH(2)CHCF(2)CHFCF(3) (10) or OCH(2)CH(2)SCH(2)CHCF(2)CHFCF(2)C(6)F(5) (11) and SCH(2)CH(2)OCH(2)CHCF(2)CHFCF(2)C(6)F(5) (12), respectively. Fluorinated alcohols C(6)F(5)CF(2)CHFCF(2)C(CH(3))(2)OH (15), C(6)F(5)CF(2)CHFCF(2)CH(CH(3))OH (16), and C(6)F(5)CF(2)CHFCF(2)CH(2)OH (17) are prepared by reacting perfluoroallylbenzene with the corresponding alcohols. When 15 is reacted with pentafluorobenzonitrile in the presence of potassium carbonate, an unexpected cyclic ether 19 is obtained as the major product in addition to C(6)F(5)CF(2)CHFCF(2)C(CH(3))(2)OC(6)F(5)CN (18). Alcohols 15-17 can be cyclized by heating with potassium carbonate to give fluorinated cyclic ethers 19-21. The X-ray crystal structures of acyclic ether 18 and cyclic ether 19 are given. Compound 18 crystallizes in the tetragonal system, space group P4(2)/n, with a = 18.471(0) ?, b = 18.471(0) ?, c = 11.702(0) ?, V = 3992.5(9) ?(3), D(calc) = 1.768 mg/m(3), Z = 8, and R = 0.0617. Compound 19 crystallizes in the triclinic system, space group P&onemacr;, with a = 8.103(3) ?, b = 8.790(3) ?, c = 9.832(3) ?, alpha = 66.25(4) degrees, beta = 72.01(3) degrees, gamma = 80.19(4) degrees, V = 608.7(4) ?(3), D(calc) = 1.845 mg/m(3), Z = 2, and R = 0.0346.     

Phase relationships in the BaO-Ga2O3-Ta2O5 system and the structure of Ba6Ga21TaO40

Phase relationships in the BaO-Ga(2)O(3)-Ta(2)O(5) ternary system at 1200 °C were determined. The A(6)B(10)O(30) tetragonal tungsten bronze (TTB) related solution in the BaO-Ta(2)O(5) subsystem dissolved up to ~11 mol % Ga(2)O(3), forming a ternary trapezoid-shaped TTB-related solid solution region defined by the BaTa(2)O(6), Ba(1.1)Ta(5)O(13.6), Ba(1.58)Ga(0.92)Ta(4.08)O(13.16), and Ba(6)GaTa(9)O(30) compositions in the BaO-Ga(2)O(3)-Ta(2)O(5) system. Two ternary phases Ba(6)Ga(21)TaO(40) and eight-layer twinned hexagonal perovskite solid solution Ba(8)Ga(4-x)Ta(4+0.6x)O(24) were confirmed in the BaO-Ga(2)O(3)-Ta(2)O(5) system. Ba(6)Ga(21)TaO(40) crystallized in a monoclinic cell of a = 15.9130(2) ?, b = 11.7309(1) ?, c = 5.13593(6) ?, β = 107.7893(9)°, and Z = 1 in space group C2/m. The structure of Ba(6)Ga(21)TaO(40) was solved by the charge flipping method, and it represents a three-dimensional (3D) mixed GaO(4) tetrahedral and GaO(6)/TaO(6) octahedral framework, forming mixed 1D 5/6-fold tunnels that accommodate the Ba cations along the c axis. The electrical property of Ba(6)Ga(21)TaO(40) was characterized by using ac impedance spectroscopy.     

Dititanium complexes of preorganized binucleating bis(amidinates)

Four different dianionic bis(amidinate) ligands ((iPr)L(DBF)(2)(-), (tBu,Et)L(DBF)(2)(-), (iPr)L(Xan)(2)(-), (tBu,Et)L(Xan)(2)(-)) featuring rigid dibenzofuran (DBF) and 9,9-dimethylxanthene (Xan) backbones have been used to prepare several new dititanium complexes. Reaction of the free-base bis(amidines) (LH(2)) with 2 equiv of Ti(NMe(2))(4) forms the hexaamido derivatives (iPr)L(DBF)Ti(2)(NMe(2))(6) (1), (tBu,Et)L(DBF)Ti(2)(NMe(2))(6) (2), (iPr)L(Xan)Ti(2)(NMe(2))(6) (3), and (tBu,Et)L(Xan)Ti(2)(NMe(2))(6) (4) in good yields. Compound 4, which features an unsymmetrically substituted bis(amidinate) ligand, was isolated as an 8:1 mixture of rotational diastereomers with C(2) and C(s)() symmetry, respectively. The two diastereomers interconvert upon heating, and at equilibrium the C(2) isomer is preferred thermodynamically by 0.2 kcal/mol. Compound 3 reacts with excess Me(3)SiCl in toluene to form the mixed amido-chloride derivative (iPr)L(Xan)Ti(2)(NMe(2))(2)Cl(4) (5) in low-moderate yield. Alternatively, 5 is also prepared by reaction of (iPr)L(Xan)H(2) with 2 equiv of Ti(NMe(2))(2)Cl(2) in good yield. Compound 3 reacts with CO(2) to form the red carbamate derivative (iPr)L(Xan)Ti(2)(NMe(2))(4)(O(2)CNMe(2))(2) (6) in moderate yield. Infrared data for 6 indicates bidentate coordination of the carbamate ligands. Metathesis reaction of (iPr)L(Xan)Li(2) with 2 equiv of CpTiCl(3) affords (iPr)L(Xan)Ti(2)Cp(2)Cl(4) (7) in moderate yield. Reduction of 7 with 1% Na amalgam in toluene solution affords the paramagnetic dititanium(III) complex (iPr)L(Xan)Ti(2)Cp(2)Cl(2) (8) in good yield. Structural studies reveal that 8 features two bridging chloride ligands. Reaction of the free-base bis(amidines) with 2 equiv of CpTiMe(3) forms the red sigma-alkyl derivatives (iPr)L(DBF)Ti(2)Cp(2)Me(4) (9), (tBu,Et)L(DBF)Ti(2)Cp(2)Me(4) (10), and (iPr)L(Xan)Ti(2)Cp(2)Me(4) (11) in good yields. Structural data are presented for compounds 4, 5, 8, and 9.     

Synthesis and Characterization of Sterically Encumbered Derivatives of Aluminum Hydrides and Halides: Assessment of Steric Properties of Bulky Terphenyl Ligands

The synthesis and characterization of several sterically encumbered monoterphenyl derivatives of aluminum halides and aluminum hydrides are described. These compounds are [2,6-Mes(2)C(6)H(3)AlH(3)LiOEt(2)](n)() (1), (Mes = 2,4,6-Me(3)C(6)H(2)-), 2,6-Mes(2)C(6)H(3)AlH(2)OEt(2) (2), [2,6-Mes(2)C(6)H(3)AlH(2)](2) (3), 2,6-Mes(2)C(6)H(3)AlCl(2)OEt(2) (4), [2,6-Mes(2)C(6)H(3)AlCl(3)LiOEt(2)](n)() (5), [2,6-Mes(2)C(6)H(3)AlCl(2)](2) (6), TriphAlBr(2)OEt(2) (7), (Triph = 2,4,6-Ph(3)C(6)H(2)-), [2,6-Trip(2)C(6)H(3)AlH(3)LiOEt(2)](2) (8) (Trip = 2,4,6-i-Pr(3)C(6)H(2)-), 2,6-Trip(2)C(6)H(3)AlH(2)OEt(2) (9), [2,6-Trip(2)C(6)H(3)AlH(2)](2) (10), 2,6-Trip(2)C(6)H(3)AlCl(2)OEt(2) (11), and the partially hydrolyzed derivative [2,6-Trip(2)C(6)H(3)Al(Cl)(0.68)(H)(0.32)(&mgr;-OH)](2).2C(6)H(6) (12). The structures of 2, 3a, 4, 6, 7, 9a, 10a, 10b, 11, and 12 were determined by X-ray crystallography. The structures of 3a, 9a, 10a, and 10b, are related to 3, 9, and 10, respectively, by partial occupation of chloride or hydride by hydroxide. The compounds were also characterized by (1)H, (13)C, (7)Li, and (27)Al NMR and IR spectroscopy. The major conclusions from the experimental data are that a single ortho terphenyl substituent of the kind reported here are not as effective as the ligand Mes (Mes = 2,4,6-t-Bu(3)C(6)H(2)-) in preventing further coordination and/or aggregation involving the aluminum centers. In effect, one terphenyl ligand is not as successful as a Mes substituent in masking the metal through agostic and/or steric effects.     

High-resolution observation and analysis of the I(2) (+) A(2)Π(3∕2,u)-X (2)Π(3∕2,g) system

Rotationally resolved absorption spectra of I(2) (+) were recorded in 12 065-13 062 cm(-1) region by employing optical heterodyne velocity modulation absorption spectroscopy. In total, 4054 lines were assigned to 24 bands in the A(2)Π(3∕2,u)-X(2)Π(3∕2,g) system spanning the vibrational levels υ(') = 1-4 and υ(n) (') = 11-19. The assigned lines were globally fitted and an error of 0.003 cm(-1) was obtained. Rotational constants, B(υ), were used to derive equilibrium parameters B(e) (') = 0.03977725(77) cm(-1), a(e) (') = 1.1819(24)×10(-4) cm(-1), r(e) (') = 2.584386(25) A? of the X(2)Π(3∕2,g) state, and B(e) (') = 0.0305787(37) cm(-1), a(e) (') = 1.2353(23)×10(-4) cm(-1), r(e) (') = 2.94758(18) A? of the A(2)Π(3∕2,u) state. Vibrational energies were used to derive ω(e) (') = 239.0397(55) cm(-1), ω(e)x(e) (') = 0.64951(87) cm(-1) of the X(2)Π(3∕2,g) state and ω(e) (') = 138.103(11) cm(-1), ω(e)x(e) (') = 0.45027(34) cm(-1) of the A(2)Π(3∕2,u) state. The A(2)Π(3∕2,u) (υ(n) = 13) state was found to be rotationally perturbed by the a(4)Σ(1/2,u) (-) (υ(n) = 17) state through second-order spin-orbit coupling.     

Al and Zn complexes bearing N,N,N-tridentate quinolinyl anilido-imine ligands: synthesis, characterization and catalysis in l-lactide polymerization

Reactions of N,N,N-tridentate quinolinyl anilido-imine ligands with AlMe(3) afford mononuclear aluminum complexes {κ(3)-[{2-[ArN[double bond, length as m-dash]C(H)]C(6)H(4)}N(8-C(9)H(6)N)]}AlMe(2) (Ar = 2,6-Me(2)C(6)H(3) (1a), 2,6-Et(2)C(6)H(3) (1b), 2,6-(i)Pr(2)C(6)H(3) (1c)) or dinuclear complexes AlMe(3){κ(1)-[{2-[ArN[double bond, length as m-dash]C(H)C(6)H(4)]N(8-C(9)H(6)N)}-κ(2)]AlMe(2) (R = 2,6-Me(2)C(6)H(3) (2a), 2,6-Et(2)C(6)H(3) (2b), 2,6-(i)Pr(2)C(6)H(3) (2c)) depending on the ratios of reactants used. Similar reactions of ZnEt(2) with these ligands give the monoligated ethyl zinc complexes {κ(3)-[{2-[ArN[double bond, length as m-dash]C(H)]C(6)H(4)}N(8-C(9)H(6)N)]}ZnEt (Ar = 2,6-Me(2)C(6)H(3) (3a), 2,6-Et(2)C(6)H(3) (3b), 2,6-(i)Pr(2)C(6)H(3) (3c)) or bisligated complexes {κ(3)-[{2-[ArN[double bond, length as m-dash]C(H)]C(6)H(4)}N(8-C(9)H(6)N)]}Zn{κ(2)-[{2-[ArN[double bond, length as m-dash]C(H)]C(6)H(4)}N(8-C(9)H(6)N)]} (Ar = 2,6-Me(2)C(6)H(3) (4a), 2,6-Et(2)C(6)H(3) (4b), 2,6-(i)Pr(2)C(6)H(3) (4c)). These complexes were well characterized by NMR and the structures of 1a, 2a, 2c, 3b and 4c were confirmed by X-ray diffraction analysis. The aluminum and zinc complexes were tested to initiate lactide polymerization in which the zinc complexes show moderate to high activities in the presence of benzyl alcohol.     

Electrophilic substitution of the nido-dicarbaborate anion 7,8-nido-C2B9H12- with sulfenyl chlorides

Sulfenyl chlorides RSCl (R = p-C(6)H(4)OMe, Ph, p-C(6)H(4)NO(2), CN or 2-C(5)H(4)N) react with 7,8-nido-C(2)B(9)H(12)(-) with asymmetric substitution on the pentagonal C(2)B(3) face to give 9-RS-7,8-nido-C(2)B(9)H(11)(-) (R = p-C(6)H(4)OMe (3), Ph (4), p-C(6)H(4)NO(2) (5), CN (6)) and the zwitterion 9-(S-2-C(5)H(4)NH)-7,8-nido-C(2)B(9)H(11) (7), respectively, in high yield, while tBuSCl did not react and S(2)Cl(2) led to decomposition. Further reaction of 5-7 with iodine gave the corresponding iodo derivatives NMe(4) [9-I-11-RS-7,8-nido-C(2)B(9)H(10)] (R = p-C(6)H(4)NO(2) (8), CN (9)) and the zwitterion 9-I-11-(S-2-C(5)H(4)NH)-7,8-nido-C(2)B(9)H(11) (10), respectively. Compounds 3-10 were fully characterised by (1)H, (11)B, (11)B{(1)H}, (13)C{(1)H} spectroscopy, IR spectroscopy, mass spectrometry and elemental analysis, 3-7 also by (11)B-(11)B{(1)H} COSY NMR spectroscopy and 8-10 by X-ray structure determination.     

Organic-inorganic hybrid materials: hydrothermal syntheses and structural characterization of bimetallic organophosphonate oxides of the type Mo/Cu/O/RPO(3)(2-)/organoimine

The hydrothermal reactions of a Cu(II) starting material, a molybdate source, 2,2'-bipyridine or terpyridine, and the appropriate alkyldiphosphonate ligand yield two series of bimetallic organophosphonate hybrid materials of the general types [Cu(n)(bpy)(m)Mo(x)O(y)(H(2)O)(p)[O(3)P(CH(2))(n)PO(3)](z)] and [Cu(n)(terpy)(m)Mo(x)O(y)(H(2)O)(p)[O(3)P(CH(2))(n)PO(3)](z)]. The bipyridyl series includes the one-dimensional materials [Cu(bpy)(MoO(2))(H(2)O)(O(3)PCH(2)PO(3))] (1) and [[Cu(bpy)(2)][Cu(bpy)(H(2)O)](Mo(5)O(15))(O(3)PCH(2)CH(2)CH(2)CH(2)PO(3))].H(2)O (5.H(2)O) and the two-dimensional hybrids [Cu(bpy)(Mo(2)O(5))(H(2)O)(O(3)PCH(2)PO(3))].H(2)O (2.H(2)O), [[Cu(bpy)](2)(Mo(4)O(12))(H(2)O)(2)(O(3)PCH(2)CH(2)PO(3))].2H(2)O (3.2H(2)O), and [Cu(bpy)(Mo(2)O(5))(O(3)PCH(2)CH(2)CH(2)PO(3))](4). The terpyridyl series is represented by the one-dimensional [[Cu(terpy)(H(2)O)](2)(Mo(5)O(15))(O(3)PCH(2)CH(2)PO(3))].3H(2)O (7.3H(2)O) and the two-dimensional composite materials [Cu(terpy)(Mo(2)O(5))(O(3)PCH(2)PO(3))] (6) and [[Cu(terpy)](2)(Mo(5)O(15))(O(3)PCH(2)CH(2)CH(2)PO(3))] (8). The structures exhibit a variety of molybdate building blocks including isolated [MoO(6)] octahedra in 1, binuclear subunits in 2, 4, and 6, tetranuclear embedded clusters in 3, and the prototypical [Mo(5)O(15)(O(3)PR)(2)](4-) cluster type in 5, 7, and 8. These latter materials exemplify the building block approach to the preparation of extended structures.     

Transition metal chemistry of cyclodiphosphanes containing phosphine and amide-phosphine functionalities: formation of a stable dipalladium(II) complex containing a Pd-P σ-bond

Cyclodiphosphazanes containing phosphine or phosphine plus amide functionalities {((t)BuNP(OC(6)H(4)PPh(2)-o)}(2) (3), {(t)BuNP(OCH(2)CH(2)PPh(2))}(2) (4), {(t)BuHN((t)BuNP)(2)OC(6)H(4)PPh(2)-o} (5), and {(t)BuHN((t)BuNP)(2)OCH(2)CH(2)PPh(2)} (6) were synthesized by reacting cis-{(t)BuNPCl}(2) (1) and cis-[(t)BuHN((t)BuNP)(2)Cl] (2) with corresponding phosphine substituted nucleophiles. The reactions of 3 and 5 with excess of elemental sulfur or selenium produce the corresponding tetra and trichalcogenides, {((t)BuNP(E)(OC(6)H(4)P(E)Ph(2)-o)}(2) (7, E = S; 8, E = Se) and {(t)BuHN((t)BuNP)(2)OC(6)H(4)P(E)Ph(2)-o} (9, E = S; 10, E = Se), respectively, in quantitative yields. The reactions between 3 and [Rh(COD)Cl](2) or [M(COD)Cl](2) (M = Pd or Pt) afford bischelated complexes [Rh(CO)Cl{(t)BuNP(OC(6)H(4)PPh(2)-o)}](2) (11), and [MCl(2){(t)BuNP(OC(6)H(4)PPh(2)-o)}](2) (12, M = Pd; 13, M = Pt) in good yield. The 1 : 2 reaction between 3 and [PdCl(η(3)-C(3)H(5))](2) in dichloromethane resulted initially in the formation of a tripalladium complex of the type [Pd(3)Cl(4)(η(3)-C(3)H(5))(2){(t)BuNPOC(6)H(4)PPh(2)}(2)] (14a) which readily reacts with moisture to form an interesting binuclear complex, [Cl(2)Pd{μ-(PPh(2)C(6)H(4)OP(μ-(t)BuN)(2)P(O)}(μ-Cl)Pd(OC(6)H(4)PPh(2))] (14b). One of the palladium(II) atoms forms a simple six-membered chelate ring, whereas the other palladium(II) atom facilitates the moisture assisted cleavage of one of the endocyclic P-O bonds followed by the oxidation of P(III) to P(V) thus forming a Pd-P σ-bond. The broken ortho-phosphine substituted phenoxide ion forms a five-membered palladacycle with the same palladium(II) atom. Similar reaction of 5 with [PdCl(η(3)-C(3)H(5))](2) also affords a binuclear complex [{PdCl(η(3)-C(3)H(5))}(t)BuNH{(t)BuNP}(2)OC(6)H(4)PPh(2){PdCl(2)}] (15) containing a PdCl(2) moiety which forms a six-membered chelate ring via ring-phosphorus and PPh(2) moieties on one side and a PdCl(η(3)-C(3)H(5)) fragment coordinating to amide bound phosphorus atom on the other side of the ring. Treatment of 3 with four equivalents of AuCl(SMe(2)) produces a tetranuclear complex, [(AuCl)(4){(t)BuNP(OC(6)H(4)PPh(2))}(2)] (16), whereas a 1 : 3 reaction between 5 and AuCl(SMe(2)) leads to the formation of a trinuclear complex, [(t)BuNH{(t)BuNP(AuCl)}(2)OC(6)H(4)P(AuCl)Ph(2)] (17). The crystal structures of 3, 5, 9-11 and 13-17 are reported.     

Aluminium complexes containing bidentate and symmetrical tridentate pincer type pyrrolyl ligands: synthesis, reactions and ring opening polymerization

A series of aluminium derivatives containing substituted bidentate and symmetrical tridentate pyrrolyl ligands, [C(4)H(3)NH(2-CH(2)NH(t)Bu)] and [C(4)H(2)NH(2,5-CH(2)NH(t)Bu)(2)], in toluene or diethyl ether were synthesized. Their reactivity and application for the ring opening polymerization of ε-caprolactone have been investigated. The reaction of AlMe(3) with one equiv. of [C(4)H(3)NH(2-CH(2)NH(t)Bu)] in toluene at room temperature affords [C(4)H(3)N(2-CH(2)NH(t)Bu)]AlMe(2) (1) in 70% yield by elimination of one equiv. of methane. Interestingly, while reacting AlMe(3) with one equiv. of [C(4)H(3)NH(2-CH(2)NH(t)Bu)] in toluene at 0 °C followed by refluxing at 100 °C, [{C(4)H(3)N(2-CH(2)N(t)Bu)}AlMe](2) (2) has been isolated via fractional recrystalliztion in 30% yield. Similarly, reacting AlMe(3) with two equiv. of C(4)H(3)NH(2-CH(2)NH(t)Bu) generates [C(4)H(3)N(2-CH(2)NH(t)Bu)](2)AlMe (3) in a moderate yield. Furthermore, complex 1 can be transformed to an aluminium alkoxide derivative, [C(4)H(3)N(2-CH(2)NH(t)Bu)][OC(6)H(2)(-2,6-(t)Bu(2)-4-Me)]AlMe (4) by reacting 1 with one equiv. of HOC(6)H(2)(-2,6-(t)Bu(2)-4-Me) in toluene via the elimination of one equiv. of methane. The reaction of AlR(3) with one equiv. of [C(4)H(2)NH(2,5-CH(2)NH(t)Bu)(2)] in toluene at room temperature affords [C(4)H(2)N(2,5-CH(2)NH(t)Bu)(2)]AlR(2) (5, R = Me; 6, R = Et) in moderate yield. Surprisingly, from the reaction of two equiv. of [C(4)H(2)NH(2,5-CH(2)NH(t)Bu)(2)] with LiAlH(4) in diethyl ether at 0 °C, a novel complex, [C(4)H(2)N(2-CH(2)N(t)Bu)(5-CH(2)NH(t)Bu)](2)AlLi (7) has been isolated after repeating re-crystallization. Furthermore, reacting one equiv. of C(4)H(2)NH(2,5-CH(2)NH(t)Bu)(2) with AlH(3)·NMe(3) in diethyl ether generates an aluminium dihydride complex, [C(4)H(2)N(2,5-CH(2)NH(t)Bu)(2)]AlH(2) (8), in high yield. Additionally, treating 8 with one equiv. of HOC(6)H(2)(-2,6-(t)Bu(2)-4-Me) in methylene chloride produces [C(4)H(2)N(2,5-CH(2)NH(t)Bu)(2)][OC(6)H(2)(-2,6-(t)Bu(2)-4-Me)]AlH (9) with the elimination of one equiv. of H(2). The aluminium alkoxide complex 4 shows moderate reactivity toward the ring opening polymerization of ε-caprolatone in toluene.     

Controlled assembly of ruthenium complexes through ortho-carborane dithiolate and polysulfide ligands

Treatment of ortho-carborane, n-butyl lithium, sulfur, and [(p-cymene)RuCl(2)](2) in varying ratio led to four new compounds (p-cymene)Ru[S(3)(C(2)B(10)H(10))(2)] (3), [(p-cymene)Ru(2)(μ(2)-S(2)C(2)B(10)H(9))(μ(3)-S(2)C(2)B(10)H(10))](2) (4), [(p-cymene)Ru](2)Ru(μ(2)-η(2):η(2)-S(2)) (μ(2)-η(2):η(1)-S(2)Cl)(μ(2)-S(2)C(2)B(10)H(10))(2) (5), and [(p-cymene)Ru](2)Ru(μ(2)-η(1):η(1)-S(2))(μ(3)-η(2):η(2)-S(4)) (μ(2)-S(2)C(2)B(10)H(10))(2) (6), respectively. In 3, the ruthenium atom is coordinated by three S atoms from a in situ generated tridentate [S(3)(C(2)B(10)H(10))(2)](2-) ligand. 4 consists of two identical dinuclear (p-cymene)Ru(2)(μ(2)-S(2)C(2)B(10)H(9))(μ(3)-S(2)C(2)B(10)H(10)) subunits which connect to each other via the Ru-Ru bond and two bridging o-carborane-1,2-dithiolate ligands. In 4, a Ru-B bond is present. 5 contains a Ru(3)(μ(2)-S)(2)(μ(2)-S(2))(μ(2)-S(2)Cl) core, and the central ruthenium atom is coordinated by seven S atoms in a distorted pentagonal bipyramidal geometry. In 5, a S-Cl bond is generated. 6 has a novel Ru(3)(μ(2)-S)(2)(μ(2)-S(2))(μ(3)-S(4)) core, and the three ruthenium atoms are connected through the two terminal sulfur atoms of the S-S-S-S chain in a μ(3) binding fashion. All the four complexes have been characterized by elemental analysis, mass, NMR, and X-ray crystallography.     

Synthesis of mono- and dihalogenated derivatives of (Me2S)2B12H10 and palladium-catalyzed boron-carbon cross-coupling reactions of the iodides with grignard reagents

Two series of compounds, 9-X-1,7-(Me(2)S)(2)B(12)H(9) and 9,10-X(2)-1,7-(Me(2)S)(2)B(12)H(8) (X = Cl, Br, I), have been synthesized from reactions of 1,7-(Me(2)S)(2)B(12)H(10) with various halogenating reagents. In addition, reactions of 1,7-(Me(2)S)(2)B(12)H(10) with 2,4-(NO(2))(2)C(6)H(3)SCl and PhSeBr resulted in 9-(2',4'-(NO(2))(2)C(6)H(3)S)-1,7-(Me(2)S)(2)B(12)H(9) and 9,10-(PhSe)(2)-1,7-(Me(2)S)(2)B(12)H(8), respectively. X-ray studies of the dibromo, monoiodo, and aryl thioether derivatives show that electrophilic substitution in 1,7-(Me(2)S)(2)B(12)H(10) takes place at positions 9 and 10, as in the case of the meta-carborane 1,7-C(2)B(10)H(12). From 1,12-(Me(2)S)(2)B(12)H(10) the halides 2-X-1,12-(Me(2)S)(2)B(12)H(9) (X = Br, I) were prepared. For both 1,7- and 1,12-(Me(2)S)(2)B(12)H(10) the best iodination results were obtained using iodine monochloride in refluxing acetonitrile. In the presence of 5 mol % (PPh(3))(2)PdCl(2) the iodides 9-I-1,7-(Me(2)S)(2)B(12)H(9), 2-I-1,12-(Me(2)S)(2)B(12)H(9), and 9,10-I(2)-1,7-(Me(2)S)(2)B(12)H(8) react with RMgX (R = Me, Ph, Bn; X = Cl, Br) in THF to yield the corresponding B-alkyl- and B-aryl-substituted products in good yields without using CuI as a cocatalyst. The bromo derivative 9-Br-1,7-(Me(2)S)(2)B(12)H(9) did not react under similar conditions. No interference from the nearby Me(2)S substituent was observed in palladium-catalyzed substitution of iodide in 2-I-1,12-(Me(2)S)(2)B(12)H(9). Presumably due to the intramolecular activation of an aryl C-H bond of the benzyl substituent in the intermediate palladium complex, the yield of 9,10-Bn(2)-1,7-(Me(2)S)(2)B(12)H(8) was significantly lower than those of the dimethyl and diphenyl derivatives. The molecular structures of 9-R-1,7-(Me(2)S)(2)B(12)H(9) (R = Ph, Bn) and 2-Bn-1,12-(Me(2)S)(2)B(12)H(9) were obtained by single-crystal X-ray analysis.     

Atmospheric chemistry of isoflurane, desflurane, and sevoflurane: kinetics and mechanisms of reactions with chlorine atoms and OH radicals and global warming potentials

The smog chamber/Fourier-transform infrared spectroscopy (FTIR) technique was used to measure the rate coefficients k(Cl + CF(3)CHClOCHF(2), isoflurane) = (4.5 ± 0.8) × 10(-15), k(Cl + CF(3)CHFOCHF(2), desflurane) = (1.0 ± 0.3) × 10(-15), k(Cl + (CF(3))(2)CHOCH(2)F, sevoflurane) = (1.1 ± 0.1) × 10(-13), and k(OH + (CF(3))(2)CHOCH(2)F) = (3.5 ± 0.7) × 10(-14) cm(3) molecule(-1) in 700 Torr of N(2)/air diluent at 295 ± 2 K. An upper limit of 6 × 10(-17) cm(3) molecule(-1) was established for k(Cl + (CF(3))(2)CHOC(O)F). The laser photolysis/laser-induced fluorescence (LP/LIF) technique was employed to determine hydroxyl radical rate coefficients as a function of temperature (241-298 K): k(OH + CF(3)CHFOCHF(2)) = (7.05 ± 1.80) × 10(-13) exp[-(1551 ± 72)/T] cm(3) molecule(-1); k(296 ± 1 K) = (3.73 ± 0.08) × 10(-15) cm(3) molecule(-1), and k(OH + (CF(3))(2)CHOCH(2)F) = (9.98 ± 3.24) × 10(-13) exp[-(969 ± 82)/T] cm(3) molecule(-1); k(298 ± 1 K) = (3.94 ± 0.30) × 10(-14) cm(3) molecule(-1). The rate coefficient of k(OH + CF(3)CHClOCHF(2), 296 ± 1 K) = (1.45 ± 0.16) × 10(-14) cm(3) molecule(-1) was also determined. Chlorine atoms react with CF(3)CHFOCHF(2) via H-abstraction to give CF(3)CFOCHF(2) and CF(3)CHFOCF(2) radicals in yields of approximately 83% and 17%. The major atmospheric fate of the CF(3)C(O)FOCHF(2) alkoxy radical is decomposition via elimination of CF(3) to give FC(O)OCHF(2) and is unaffected by the method used to generate the CF(3)C(O)FOCHF(2) radicals. CF(3)CHFOCF(2) radicals add O(2) and are converted by subsequent reactions into CF(3)CHFOCF(2)O alkoxy radicals, which decompose to give COF(2) and CF(3)CHFO radicals. In 700 Torr of air 82% of CF(3)CHFO radicals undergo C-C scission to yield HC(O)F and CF(3) radicals with the remaining 18% reacting with O(2) to give CF(3)C(O)F. Atmospheric oxidation of (CF(3))(2)CHOCH(2)F gives (CF(3))(2)CHOC(O)F in a molar yield of 93 ± 6% with CF(3)C(O)CF(3) and HCOF as minor products. The IR spectra of (CF(3))(2)CHOC(O)F and FC(O)OCHF(2) are reported for the first time. The atmospheric lifetimes of CF(3)CHClOCHF(2), CF(3)CHFOCHF(2), and (CF(3))(2)CHOCH(2)F (sevoflurane) are estimated at 3.2, 14, and 1.1 years, respectively. The 100 year time horizon global warming potentials of isoflurane, desflurane, and sevoflurane are 510, 2540, and 130, respectively. The atmospheric degradation products of these anesthetics are not of environmental concern.