Steven H. Strauss

Occurrence and persistence of perfluorooctanesulfonate and other perfluorinated surfactants in groundwater at a fire-training area at Wurtsmith Air Force Base, Michigan, USA

Various formulations of fire-extinguishing materials, including aqueous film-forming foams (AFFFs), were used as part of fire-training exercises conducted at Wurtsmith Air Force Base (WAFB) in northeastern Michigan from the 1950s until the base was decommissioned in 1993. As a result of past fire-training exercises, AFFF-laden wastewater containing fuels, solvents, and other materials directly entered groundwater without prior treatment. Perfluorinated surfactants are key components in some AFFF formulations. In this study, groundwater was analyzed for perfluoroalkanesulfonates and perfluorocarboxylates. Perfluoroalkanesulfonates were directly detected using negative-ion electrospray ionization mass spectrometry. Derivatized perfluorocarboxylates were detected using electron impact gas chromatography-mass spectrometry. Groundwater from wells around fire-training area FTA-02 at WAFB contained four perfluorinated surfactants ranging in concentration from 3 to 120 microg L(-1): perfluorooctanesulfonate (PFOS); perfluorohexanesulfonate; perfluorooctanoate; and perfluorohexanoate. This is the first report demonstrating that PFOS, recently shown to be toxic to organisms ranging from zooplankton to primates, is still present in groundwater in measurable quantities five or more years after its last known use.

Nonclassical Metal Carbonyls: Appropriate Definitions with a Theoretical Justification

MP2 calculations show that the D∞h isoelectronic dicarbonyl complexes [M(CO)2 ]n (Mn =Rh- , Pd0 , Cu+ , Ag+ , Au+ , Zn2+ , Cd2+ , Hg2+ ) depicted in structure 1 can be classified as classical or nonclassical depending on whether the metal-carbon bond lengths decrease or increase when weak, anionic ligands approach the metal centers.

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.

Trends in Molecular Geometries and Bond Strengths of the Homoleptic d10 Metal Carbonyl Cations [M(CO)n]x+ (Mx+=Cu+, Ag+, Au+, Zn2+, Cd2+, Hg2+; n=1–6): A Theoretical Study

Surprising trendsin the M–CO bond dissociation energies (see illustration; n = number of carbonyl ligands) are revealed by quantum chemical calculations for the title molecules. Analysis of the bonding interactions reveals an interplay of coulombic and covalent interactions between the metal cations and CO. Theoretical predictions are made for strongly bound carbonyl complexes which have not yet been synthesized.

A Buckybowl with a Lot of Potential: C5-C20H5(CF3)5†

Lots of potential: a trifluoromethylated corannulene, C(5)-C(20)H(5)(CF(3))(5), has been prepared and characterized spectroscopically and by X-ray crystallography. The structure exhibits a highly ordered bowl stacking that is unusual for corannulenes with acyclic substituents. The first reduction of C(5)-C(20)H(5)(CF(3))(5) is anodically shifted by 0.95 V, making it the strongest corannulene-based electron acceptor to date.

Electronic structure of CO--an exercise in modern chemical bonding theory.

This paper discusses recent progress that has been made in the understanding of the electronic structure and bonding situation of carbon monoxide which was analyzed using modern quantum chemical methods. The new results are compared with standard models of chemical bonding. The electronic charge distribution and the dipole moment, the nature of the HOMO and the bond dissociation energy are discussed in detail.

Direct Perfluorination of K2B12H12 in Acetonitrile Occurs at the Gas Bubble−Solution Interface and Is Inhibited by HF. Experimental and DFT Study of Inhibition by Protic Acids and Soft, Polarizable Anions

During the optimization of the F(2) perfluorination of K(2)B(12)H(12) in acetonitrile with continuous bubbling of 20/80 F(2)/N(2), it was discovered that (i) HF and other protic acids inhibit each of the 12 fluorination steps (in contradiction to recently published findings) and (ii) the fluorinations appear to take place at the gas bubble-solution interface. Experimental results and DFT calculations suggest that these two phenomena are related by the relative propensities of the various B(12)H(12-x)F(x)(2-) anions to partition from bulk solution to the interface (i.e., their relative polarizabilities or softness; 0 <or= x <or= 12). Relative to the previously reported syntheses of K(2)B(12)F(12) or Cs(2)B(12)F(12), the new optimized procedure has the following advantages: (i) the scale was increased 10-fold without sacrificing yield (74% for K(2)B(12)F(12), 76% for Cs(2)B(12)F(12)) or purity (99.5+%); (ii) the reaction/purification time was decreased from ca. 1 week to 2 days; and (iii) the solvent was changed from anhydrous HF to acetonitrile, allowing ordinary glassware to be used. The anhydrous salt Cs(2)B(12)F(12) was found to be thermally stable up to 600 degrees C.

Poly(perfluoroalkylation) of Metallic Nitride Fullerenes Reveals Addition-Pattern Guidelines: Synthesis and Characterization of a Family of Sc3N@C80(CF3)n (n = 2−16) and Their Radical Anions

A family of highly stable (poly)perfluoroalkylated metallic nitride cluster fullerenes was prepared in high-temperature reactions and characterized by spectroscopic (MS, (19)F NMR, UV-vis/NIR, ESR), structural and electrochemical methods. For two new compounds, Sc(3)N@C(80)(CF(3))(10) and Sc(3)N@C(80)(CF(3))(12,) single crystal X-ray structures are determined. Addition pattern guidelines for endohedral fullerene derivatives with bulky functional groups are formulated as a result of experimental ((19)F NMR spectroscopy and single crystal X-ray diffraction) studies and exhaustive quantum chemical calculations of the structures of Sc(3)N@C(80)(CF(3))(n) (n = 2-16). Electrochemical studies revealed that Sc(3)N@C(80)(CF(3))(n) derivatives are easier to reduce than Sc(3)N@C(80), the shift of E(1/2) potentials ranging from +0.11 V (n = 2) to +0.42 V (n = 10). Stable radical anions of Sc(3)N@C(80)(CF(3))(n) were generated in solution and characterized by ESR spectroscopy, revealing their (45)Sc hyperfine structure. Facile further functionalizations via cycloadditions or radical additions were achieved for trifluoromethylated Sc(3)N@C(80) making them attractive versatile platforms for the design of molecular and supramolecular materials of fundamental and practical importance.

Fluorination of deltahedral closo-borane and -carborane anions with N-fluoro reagents

Abstract The treatment of cesium salts of CB11H12, CB9H10, B12H2, and B10H102− with the commercially available N-fluoro reagent 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (F-TEDA) resulted in the formation of fluorinated derivatives of these 10- and 12-vertex borane and carborane anions. This is the first reported use of an N-fluoro reagent to fluorinate BH bonds of any type. The effects of changing the solvent, temperature, and reagent stoichiometry were studied. The derivatives 1-B10H9F2-,2-B10H9 F2, and 1,10-B10H8F22 are the first fluorinated derivatives of the parent B10H102 cluster. For the other three parent anions, reactions with F-TEDA resulted in a higher degree of fluorination than reactions with liquid anhydrous hydrogen fluoride (LAHF) at the same temperature. However, F-TEDA was found to be less regioselective than LAHF for BH → BF transformations.

C20H4(C4F8)3: A Fluorine-Containing Annulated Corannulene that Is a Better Electron Acceptor Than C60†

At sixes and sevens: The reaction of corannulene with 35 equivalents of 1,4-C4F8I2 is an efficient and a relatively selective process that yields two main products in which six H atoms are substituted with three C4F8 moieties that form six- and seven-membered rings. Low-temperature photoelectron spectroscopy showed the electron affinity of the major isomer (shown) exceeds that of C60 (2.74±0.02 and 2.689±0.008 eV, respectively).