Laura T. Smith

Quantitative analysis of slurry sample by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been employed for the analysis of slurry samples. Quantitative analysis of slurry samples is crucial and challenging. The problems associated with slurry samples include splashing, surface turbulence, and the difficulties of obtaining reproducible samples due to sedimentation. The LIBS analysis has achieved limited success due to inherent disadvantages when applied to slurry samples. In order to achieve improved measurement precision and accuracy, a spin-on-glass sampling method was evaluated. Five elements (Al, Ca, Fe, Ni, and Si) were examined in five slurry simulants containing varying amounts of each ion. Three calibration models were developed by using univariate calibration, multiple linear regression, and partial least square regression. LIBS analysis results obtained from the partial least square regression model were determined to be the best fit to results obtained from inductively coupled plasma optical emission spectroscopy analysis.

Studies towards diarylheptanoid synthesis. Part 1: Synthesis and ring cleavage reactions of hexahydro-2H, 5H-pyrano[2,3-b]pyran-2-ones

Lewis acid promoted anomeric substitution reactions of a stereoselectively prepared hexahydro-2H,5H-pyrano[2,3-b]pyran-2-one derivative was studied as a model for diarylheptanoid synthesis. Aromatic nucleophiles consistently provided the expected thermodynamic C-aryl pyranoside product.

Synthesis of multiply-bonded dichromium complexes with a variety of formamidinate ligands

Abstract A series of dichromium tetraformamidinate complexes with (ArNCHNAr)− where Ar is X2C6H3 or XC6H4 and X is the remote substituent 3,5-Cl2, 3,4-Cl2, p-Cl, p-CF3, m-CF3, p-OCH3 or m-OCH3 has been synthesized, and the structures of four of the compounds determined by X-ray crystallography. The Cr–Cr bond distances of the complexes structurally characterized are 1.9072(10) A [Cr2((p-ClC6H4N)2CH)4], 1.9162(10) A [Cr2((3,5-Cl2C6H3N)2CH)4], 1.9018((8) A [Cr2((m-CF3C6H4N)2CH)4 ], and 1.9178(11) A [Cr2((m-OCH3C6H4N)2CH)4]. 1H NMR spectroscopy and electrochemistry were performed on the series. The diamagnetic anisotropy of the Cr–Cr bond was calculated from X-ray crystallographic and 1H NMR data and correlates with the Hammett constant of the formamidine ligands.

Synthesis, characterization, and X-ray crystallography of a series of ditungsten complexes with bis(diphenylphosphino)amine

The W 2 (II, II) and W 2 (III, III) compounds, W 2 (μ-O 2 CC 6 H 5 ) 2 Cl 2 (μ-dppa) 2 ( 1 ), W 2 (μ-O 2 CC 6 H 5 ) 2 Br 2 (μ-dppa) 2 ( 2 ), W 2 (μ-O 2 CC 6 H 5 ) 2 I 2 (μ-dppa) 2 ( 3 ), W 2 Cl 4 (μ-dppa) 2 ( 4 ), W 2 (μ-Cl) 2 Cl 4 (μ-dppa) 2 ( 5 ), and W 2 (μ-H) 2 Cl 4 (μ-dppa) 2 ( 6 ), have been synthesized using the chelating phosphine ligand dppa (bis(diphenylphosphino)amine). The series of metal–metal multiply bonded complexes has been characterized by NMR and UV–vis spectroscopy, and the structures of 2 ·(THF) 2 , 5 ·(THF) 4 , and 6 ·(THF) 2 determined by X-ray crystallography.

Crystallographic and Spectroscopic Characterization of Tetrakis(μ‐N,N′‐diarylformamidinato)dichlorodirhenium(III,III) Compounds

Through a variation in the aryl substituents of the formamidinate ligand, a variety of dirhenium compounds has been synthesized with [XArNC(H)NArX]− where Ar is a substituted C6H5 or C6H4 aryl ring and × is p-MeO (1), H (3), m-MeO (4), p-Cl (5), m-Cl (6), m-CF3 (7), p-CF3 (8), 3,4-Cl2 (9), and 3,5-Cl2 (10a, 10b). UV/Vis and NMR spectroscopy and electrochemical data for 1and 3–10 have been obtained. X-ray crystallographic analysis of Re2Cl2(μ-form)4 with four different diarylformamidinate ligands and one analog with two different interstitial solvents are presented; Re2Cl2[(p-MeOC6H4)NCHN(p-MeOC6H4)]4 (1), Re2Cl2[(m-MeOC6H4)-NCHN(m-MeOC6H4)]4 · 2 CH2Cl2 (4), Re2Cl2[(3,4-Cl2C6H3)NCHN(3,4-Cl2C6H3)]4 · 2 CH2Cl2 (9), Re2Cl2[(3,5-Cl2C6H3)NCHN(3,5-Cl2C6H3)]4 · 4 CH2Cl2 (10a), and Re2Cl2[(3,5-Cl2C6H3)NCHN(3,5-Cl2C6H3)]4 · OC4H8 (10b).

Tungsten to tungsten quadruple bonds: over 30 years of research, 50 structurally characterized compounds and 100 known compounds

Abstract Since the first reported structure of a quadruply bonded ditungsten complex in 1977, the field of W 2 (II, II) chemistry has expanded as new synthetic methodologies have been developed. Based on a recently developed synthetic route in our laboratory, the synthesis and structures of two new W 2 (II, II) complexes with substituted formamidinate ligands are reported. With the addition of these two new structures, the number of structurally characterized quadruply bonded W 2 (II, II) complexes exceeds 50 and over 100 W 2 (II, II) complexes have been synthesized. A compilation of the quadruply bonded W 2 (II, II) compounds, W–W bond distances, and synthetic methodologies is presented.

The structure of (η6-C6H5Cl)Cr(CO)2PPh3

In a synthetic route that varies from the standard procedure requiring irradiation, the (η6-C6H5Cl)Cr(CO)2PPh3 complex is obtained upon reacting (η6-C6H5Cl)Cr(CO)3 with tetrakis(triphenylphosphine)palladium(0), CuI, and trimethylsilylphenylacetylene in triethylamine. The X-ray crystal structure of the yellow–orange crystals of (η6-C6H5Cl)Cr(CO)2PPh3 allows structural comparisons to related (arene)Cr(CO)2PR3 complexes.

The hydrolysis of cyanophenols at a bimetallic Re2(III, III) core

Abstract Studies of nitrile hydrolysis at the dirhenium core of [N(C4H9)4]2[Re2Cl8] were extended through both the inclusion of a series of substituted nitriles, 2-, 3-, and 4-cyanophenol and either silver or thallium salts to promote the removal of chloride from [N(C4H9)4]2[Re2Cl8]. Based on the expanded studies, steric limitations resulting from the OH group are not evident in the hydrolysis reaction for this series of benzonitriles, and the reaction resulted in the synthesis of bridging amidate ligands coordinated to the dirhenium core in [N(C4H9)4][Re2Cl6(2-HOC6H4NHC(O))] (1), [N(C4H9)4][Re2Cl6(3-HOC6H4NHC(O))] (2), and [N(C4H9)4][Re2Cl6(4-HOC6H4NHC(O))] (3), respectively. In addition to the structural and spectroscopic characterization of the series of compounds, the reactions were performed by simply heating the nitrile and [N(C4H9)4]2[Re2Cl8] in methylene chloride:alcohol solvent mixtures, and using AgBF4 and thallium(I) triflate (TlO3SCF3) to promote chloride removal in order to compare the general reaction times and yields.

The synthesis, crystal structure, and spectroscopic characterization of a tetrakis(μ-N,N′-diarylformamidinato)chlorodirhenium(III,III) cationic complex

Abstract A variety of dirhenium compounds has been synthesized with (ArNC(H)NAr)− where Ar is a substituted C6H5 or C6H4 aryl ring with different electron withdrawing and electron donating substituents. Reactivity studies of AgBF4 with tetrakis(μ-N,N′-diarylformamidinato)dichlorodirhenium(III,III) complex with a p-MeO substituted aryl ring result in the loss of a single axial chloride from the Re2Cl2(III,III) species to yield a cationic complex, [Re2Cl[(p-MeOC6H4)NCHN(p-MeOC6H4)]4][BF4] and AgCl. The X-ray crystal structure, UV–Vis and NMR spectroscopy, and electrochemical characterization of the cationic Re2Cl(III,III) derivative [Re2Cl[(p-MeOC6H4)NCHN(p-MeOC6H4)]4][BF4] are compared to the parent neutral Re2Cl2(III,III) complex, Re2Cl2[(p-MeOC6H4)NCHN(p-MeOC6H4)]4.

The structure of the dichromium compound Cr2(μ-OH)2(μ-3,5Cl2-form)2(η2-3,5Cl2-form)2

Abstract With exposure to trace amounts of air and moisture, the Cr 2 (II, II) complex Cr 2 (μ-3,5Cl 2 -form) 4 , where 3,5Cl 2 -form is [(3,5-Cl 2 C 6 H 3 )NC(H)N(3,5-Cl 2 C 6 H 3 ) − ], undergoes an oxidative addition reaction. Structural information from the X-ray crystal structure of the edge-sharing bioctahedral (ESBO) Cr 2 (III, III) product Cr 2 (μ-OH) 2 (μ-3,5Cl 2 -form) 2 (η 2 -3,5Cl 2 -form) 2 ( 1 ) indicates 1 has a significantly longer Cr–Cr distance [2.732(2) A] than Cr 2 (μ-3,5Cl 2 -form) 4 [1.9162(10) A], but the shortest Cr–Cr distance in an ESBO Cr 2 (III, III) complex recorded to date.