Oren P. Anderson

Relative Lewis Basicities of Six Al(ORF)4− Superweak Anions and the Structures of LiAl{OCH(CF3)2}4 and [1-Et-3-Me-1,3-C3H3N2][Li{Al{OCH(CF3)2}4}2]

The relative Lewis basicities of six Al(ORF)4− ions, Al{OC(CH3)(CF3)2}4−, Al{OC(CF3)3}4−, Al{OCPh(CF3)2}4−, Al{OC{4-C6H4(tBu)}(CF3)2}4−, Al{OC(Cy)(CF3)2}4−, and Al{OCPh2(CF3)}4−, have been determined by measuring their relative coordinating abilities towards Li+ in dichloromethane. The relative Li+ Lewis basicities of the Al(ORF)4− ions are linearly related to the aqueous pKa values of the corresponding parent HORF fluoroalcohols. The Lewis basicity of Al{OCH(CF3)2}4− could not be measured because two of these anions can coordinate to one Li+ cation. The structures of LiAl{OCH(CF3)2}4 and [1-Et-3-Me-1,3-C3H3N2][Li{Al{OCH(CF3)2}4}2] were determined.

Chloro-substituted dipicolinate vanadium complexes: synthesis, solution, solid-state, and insulin-enhancing properties.

Three vanadium complexes of chlorodipicolinic acid (4-chloro-2,6-dipicolinic acid) in oxidation states III, IV, and V were prepared and their properties characterized across the oxidation states. In addition, the series of hydroxylamido, methylhydroxylamido, dimethylhydroxylamido, and diethylhydroxylamido complexes were prepared from the chlorodipicolinato dioxovanadium(V) complex. The vanadium(V) compounds were characterized in solution by (51)V and (1)H NMR and in the solid-state by X-ray diffraction and (51)V NMR. Density Functional Theory (DFT) calculations were performed to evaluate the experimental parameters and further describes the electronic structure of the complex. The small structural changes that do occur in bond lengths and angles and partial charges on different atoms are minor compared to the charge features that are responsible for the majority of the electric field gradient tensor. The EPR parameters of the vanadium(IV) complex were characterized and compared to the corresponding dipicolinate complex. The chemical properties of the chlorodipicolinate compounds are discussed and correlated with their insulin-enhancing activity in streptozoticin (STZ) induced diabetic Wistar rats. The effect of the chloro-substitution on lowering diabetic hyperglycemia was evaluated and differences were found depending on the compounds oxidation state similar as was observed for the vanadium III, IV and V dipicolinate complexes (P. Buglyo, D.C. Crans, E.M. Nagy, R.L. Lindo, L. Yang, J.J. Smee, W. Jin, L.-H. Chi, M.E. Godzala III, G.R. Willsky, Inorg. Chem. 44 (2005) 5416-5427). However, a linear correlation of oxidation states with efficacy was not observed, which suggests that the differences in mode of action are not simply an issue of redox equivalents. Importantly, our results contrast the previous observation with the vanadium-picolinate complexes, where the halogen substituents increased the insulin-enhancing properties of the complex (T. Takino, H. Yasui, A. Yoshitake, Y. Hamajima, R. Matsushita, J. Takada, H. Sakurai, J. Biol. Inorg. Chem. 6 (2001) 133-142).

Synthesis and structures of poly(perfluoroethyl)[60]fullerenes: 1,7,16,36,46,49-C60(C2F5)6 and 1,6,11,18,24,27,32,35-C60(C2F5)8

The high-temperature reaction of C60 and C2F5I produced poly(perfluoroethyl)fullerenes with unprecedented addition patterns.

Crystal and molecular structure of tris-(2,2′-bipyridyl)copper(II) perchlorate

The crystal and molecular structure of the title compounds has been determined from three-dimensional single crystal X-ray diffraction data, collected by counter techniques. Crystals are triclinic, space group P, with Z= 2 in a unit cell of dimensions: a= 12·673(17), b= 18·440(21), c= 7·937(7)A, α= 90·37(14)°, β= 120·56(13)°, and γ= 98·80(11)°. The structure was refined by full-matrix least-squares methods on alternate sets of atoms to R 0·091 for 3972 observed reflections. The monomeric complex ions exhibit a distorted octahedral configuration, with unequal distortions of the axial Cu–N bonds. Mean distances: Cu–N(eq) is 2·031(6), Cu–N(ax) 2·226(7), and 2·450(7)A.

Coordination of the new weakly coordinating anions Al(OCH(CF3)2)4−, Al(OC(CH3)(CF3)2)4−, and Al(OC(Ph)(CF3)2)4− to the monovalent metal ions Li+ and Tl+

Abstract The structures of Li+ or Tl+ salts of three new fluoroalkoxide-containing aluminate anions were determined by X-ray crystallography. For LiAl(OC(Ph)(CF3)2)4, monoclinic, C2/c, a=42.297(6), b=10.641(1), c=19.132(2) A, β=114.808(9)°, Z=8, T=−100°C, R=0.052; for TlAl(OC(CH3)(CF3)2)4, monoclinic, P21/c, a=12.650(3), b=9.970(2), c=21.237(4) A, β=94.00(3)°, Z=4, T=−100°C, R=0.073; for TlAl(OCH(CF3)2)4, monoclinic, P21/n, a=14.261(1), b=9.8024(9), c=16.911(2) A, β=93.467(8), Z=4, T=−130°C, R=0.053. The monatomic, monovalent cations interact with their respective anions by means of M–O and M–F bonds. The Tl+ cations in TlAl(OCH(CF3)2)4 and TlAl(OC(CH3)(CF3)2)4 interact with three different aluminate anions. The Li+ cation in LiAl(OC(Ph)(CF3)2)4 interacts with only one aluminate anion, forming a rare trigonal–prismatic LiO2F4 coordination unit.

Nitrogen Directs Multiple Radical Additions to the 9,9′‐Bi‐1‐aza(C60‐Ih)[5,6]fullerene: X‐ray Structure of 6,9,12,15,18‐C59N(CF3)5

Azafullerenes, in which a cage carbon atom is replaced by a nitrogen atom, are the only type of heterofullerenes that can be made in practical amounts, and this makes it possible to probe the effects of cage-atom substitution on the physical and chemical properties. 4] Herein, we report a unique type of isomerism in azafullerenes bearing trifluoromethyl groups, which is attributed to the directing role of the nitrogen atom, and the first X-ray structure of the C59N derivative prepared directly from (C59N)2. Figure 1 shows the negative-ion atmospheric-pressure chemical ionization (NI APCI) mass spectra of the products of the high-temperature trifluoromethylation of (C59N)2 with CF3I obtained either in a sealed ampoule (top) or in a flow tube (bottom). The thermolysis of (C59N)2 yields a radical monomer C59NC which readily adds up to 15 (bottom spectrum) or even 19 CF3 groups per cage (top spectrum) to form closed-shell species C59N(CF3)n, where n is an odd number. In these reactions, a nonsoluble dark-brown solid dimer (C59N)2 is quantitatively converted into a volatile, thermally stable orange crystalline material, which is highly soluble in many organic and fluoroorganic solvents. When trifluoromethyl groups were added to C60 under similar conditions, the closed-shell species with even n values up to 22 were formed (see the Supporting Information). The product in the flow tube was separated by chromatography into four main fractions: I) C59N(CF3)11-15, II) C59N(CF3)9, III) C59N(CF3)7, and IV) C59N(CF3)5 (inset in Figure 1). This one-step HPLC process yielded a 98 % compositionally pure sample of C59N(CF3)5 as proven by NI APCI mass spectrometry, which detects also a single isomer with Cs symmetry (see the F NMR spectrum in Figure 2, top). The absence of terminal CF3 groups (seen as quartets in the F NMR spectra) implies that five CF3 groups should be arranged in a para 5 (or p) loop rather than as a ribbon of edge-sharing p-C6(CF3)2 hexagons as most commonly observed in the C60(CF3)n compounds. [5] The absorption spectrum (see the Supporting Information) is similar to that of Cs-C60(CF3)6. [6] The most probable addition pattern that agrees with the spectroscopic data and was previously observed for azafullerenes features an isolated pyrrole moiety on the fullerene core (Figure 1). Interestingly, C60X6 compounds with a similar addition pattern of skew-pentagonal pyramid (SPP) are formed abundantly, if not regioselectively, in various room-temperature reactions (see references in the Supporting Information). However, SPP-Cs-C60(CF3)6 was found only as a minor isomer in the high-temperature synthesis, whereas C1-C60(CF3)6 with a ribbon addition pattern (para -meta-para ; pmp) was at least ten times more abundant. 6] The Cs isomer is also 14.4 kJ mol 1 less stable than pmp-C1-C60(CF3)6 at the DFT Figure 1. Negative-ion APCI mass spectra of the C59N(CF3)n products obtained in a sealed glass ampoule at 530 8C for 24 h (top) and a hot flow tube at 500 8C for 3 h (bottom). The HPLC trace (inset) of the crude product (100% toluene eluent).

X-ray structure and DFT study of C1-C60(CF3)12. A high-energy, kinetically-stable isomer prepared at 500 °C

The title compound, prepared from C60 and CF3I at 500 °C, exhibits an unusual fullerene(X)12 addition pattern that is 40 kJ mol−1 less stable than the previously reported C60(CF3)12 isomer.

Diiron(III) complexes of some relevance to the purple acid phosphatases

Abstract Three diiron(III) complexes of the tetradentate tripodal ligand N-(-ohydroxybenzyl)-N,N-bis(2-pyridylmethyl)amine (HDP), [Fe2(HDP)2O(O2CPh)BPh4 (1), [Fe2(HDP)2O{O2P(OPh)2}]BPh4 (2), and [Fe2(HDP)2{O2(OPh)2}2](BPh4)2 (3), have been synthesized as models for the active site of the purple acid phosphtes. Single crystals of 1 ( P2 1 2 1 2 1 , a=17.728(3) A , b=18.204(4) A c=19.3383(4) A , Z=4, V=6255 A 3 ) and 3 ( P 1 , a=14.316(11) A , b=15.136(17) A , c=13.303(6) A , α=97.04(7)°, β=104.48(5)°, γ=115.51(8)°, Z=1, V=2430(6) A 3 ) were obtained and subjected to X-ray diffraction analysis. Complex 1 has a (μ-oxo)(μ-benzoato)Diiron(III) core, while complex 3 has a bis(μ-phosphato)diiron(III) core, the tetradentate HDP completing the coordination spere about each iron center in both complexes. Due to differences in their core structures, the FeFe separations in 1 and 3 are 3.217(11) A and 4.819(1) A, respectively. Complex 2 is presumed to have a structure analogous to 1 with phosphate replacing the benzoate bridge. Both 1 and 2 exhibit strong atiferromagnetic coupling due to the presence of the oxo bridge (J=−111 and −96 cm−1, respectively; H=−2JS1·S2). Interestingly, the iron(III) centers in 3 are not coupled at all; 3 exhibits Curie behavior throughout the entire temperature range studied (6–300 K) with a magnetic moment commensurate with two high-spin iron(III) centers. The three complexes exhibit visible absorption maxima at 522, 516, and 605 nm, respectively, arising from phenolate-to-iron(III) charge transfer transitions. The shifts in the λmax values can be rationalized on the basis of the Lewis acidities of the respective iron(III) centers. These are compared with those of the purple acid phosphatases.

Synthesis and characterization of the anionic fluorocarboranes 6,7,8,9,10-CB9H5F5 −, 6,7,8,9-CB9H5F4-10-OH−, and 6,7,8,9-CB9H5F4-10-NHCOCH3 −

The reactions of salts of the 6,7,8,9-CB 9 H 6 F 4  − and CB 9 H 10  − anions with 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (F-TEDA) in acetonitrile in the presence or absence of trifluoroacetic acid were studied. The addition of trifluoroacetic acid to the reaction mixture significantly changed the concentration ratio of the two pentafluoro isomers produced in the reactions, [6,7,8,9,10-CB 9 H 5 F 5  − ]/[2,6,7,8,9-CB 9 H 5 F 5  − ]. The ratio increased from 0.6 to >23 when the solvent was changed from neat acetonitrile to a 20% solution of trifluoroacetic acid in acetonitrile while simultaneously raising the temperature from 25°C to 60°C. The synthesis and 11 B and 19 F NMR spectroscopic characterization of the 6,7,8,9,10-CB 9 H 5 F 5  − anion are reported here for the first time. Chromatographic separation of the reaction mixtures led to the isolation of salts of two additional new anions, 6,7,8,9-CB 9 H 5 F 4 -10-NHCOCH 3  − and 6,7,8,9-CB 9 H 5 F 4 -10-OH − . The structure of [PPh 4 ][6,7,8,9-CB 9 H 5 F 4 -10-NHCOCH 3 ] was determined by X-ray crystallography: monoclinic, space group P 2 1 / n , a =7.5169(3), b =23.2793(10), c =16.6170(7) A, Z =4, T =−113°C, least-squares refinement on F 2 , R 1 ( I >2 σ ( I ))=0.0805, wR 2 (all data)=0.1922.

Highly polydentate ligands. Part 4. Crystal structures of neodymium(III) and erbium(III) complexes of 3,12-bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecanedioate(4–)

The structures of calcium salts of the erbium(III) and neodymium(III) chelates of the calcium-selective octadentate ligand egta4–[H4egta = 3,12-bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecanedioic acid] have been determined, in order to identify the structural changes that occur in a calcium-selective binding site when lanthanides are substituted for calcium. Ca[Er(egta)(OH2)]2·12H2O·(CH3)2CO (1) crystallizes in the monoclinic space group P21(Z= 2), with a= 12.710(2), b= 12.157(2), c= 17.765(3)A, and β= 105.79(1)°R= 0.027, R′= 0.035. Ca[Nd(egta)(OH2)]2·9H2O (2) crystallizes in the monoclinic space group P21/c(Z= 2), with a= 10.776(2), b= 18.218(4), c= 12.560(2)A, and β= 112.14(1)°; R= 0.028, R′= 0.040. The full octadentate chelating capability of egta4– is utilized in both chelates. In contrast to the eight-co-ordinate calcium ions in [Ca(egta)]2–, the ErIII ions in (1) are nine-co-ordinate; the ninth co-ordination site is occupied by a water molecule. Of the three ligand atom types, the carboxylate oxygen atoms are bound at the shortest distance [Er–O(carboxylate)av= 2.31(3)A], followed by the ether oxygen atoms [Er–O(ether)av= 2.42(5)A], and the amine nitrogen atoms [Er–Nav= 2.57(4)A]. The NdIII ions in (2) are ten-co-ordinate; ten-co-ordination is achieved in the solid state by binding a water molecule, as well as a carboxylate oxygen atom from an adjacent complex ion The order of metal–Iigand bond distances observed for NdIII is the same as that observed for ErIII Nd–O(carboxylate)av= 2.46(1), Nd–O(ether)av= 2.67(3), Nd–Nav= 2.81(7)A.