Kenton H. Whitmire

Magnetic−Plasmonic Core−Shell Nanoparticles

Nanoparticles composed of magnetic cores with continuous Au shell layers simultaneously possess both magnetic and plasmonic properties. Faceted and tetracubic nanocrystals consisting of wustite with magnetite-rich corners and edges retain magnetic properties when coated with a Au shell layer, with the composite nanostructures showing ferrimagnetic behavior. The plasmonic properties are profoundly influenced by the high dielectric constant of the mixed iron oxide nanocrystalline core. A comprehensive theoretical analysis that examines the geometric plasmon tunability over a range of core permittivities enables us to identify the dielectric properties of the mixed oxide magnetic core directly from the plasmonic behavior of the core-shell nanoparticle.

THE INTERFACE OF MAIN GROUP AND TRANSITION METAL CLUSTER CHEMISTRY

Abstract The literature concerning cluster complexes which contain both main group element and transition metal vertices is reviewed. Synthetic methods and general reactivity patterns are summarized. Emphasis is placed on structural. Comparisons of cluster geometries for a wide variety of element combinations. Relationships between these mixed clusters and the main group element clusters known as Zintl ions are discussed.

The role of metal cluster interactions in the proton-induced reduction of CO. the crystal structures of [PPN]{HFe4(CO)12} and HFe4(CO)12(η-COCH3)

Abstract The isolation and crystal structure of the iron carbonyl complex [PPN]-[HFe4(CO)12C] (I) from the reaction of [PPN]2[Fe4(CO)13] and HSO3CF3 shows it to be a carbine complex. The possible role of the carbide species in the proton-induced reaction of CO is discussed. The structurally similar complex (μ-H)Fe4(CO)12(η2-COCH3) (II) has also been prepared and its crystal structure determined. Both I and II contain carbon atoms bonded to four irons in a butterfly arrangement. In both, the hydride bridges the two cm3 (metal connectivity of three) iron atoms.

Sterically crowded aryl bismuth compounds: synthesis and characterization of bis{2,4,6-tris(trifluoromethyl)phenyl} bismuth chloride and tris{2,4,6-tris(trifluoromethyl)phenyl} bismuth

The reactions of BiCl3 with 2,4,6-tris(trifluoromethyl)phenyl lithium (LiRf) in ether solution in 1 : 2 and 1 : 3 ratios have led to the isolation of Bi(Rf)2Cl (I) and Bi(Rf)3 (II). The hexane-soluble compounds have been spectroscopically and structurally characterized I: monoclinic space group P21/c, a = 8.816(2), b = 30.459(6), c = 8.817(2)A, β = 109.58(2)°, Z = 4, V = 2230.7(8)A3;II: monoclinic space group P21/c, a = 11.769(2), b = 17.029(3), c = 16.213(3)A, β = 102.74(3)°, Z = 4, V = 3169.3(10)A3. Both compounds are monomeric in the solid state. Compound II is unstable in solution even under inert atmosphere producing RfH. In the solid state the compound is stable in inert atmosphere but decomposes slowly upon exposure to air producing RfOH and (Rf)2O. In the presence of BiCl3, II undergoes exchange to produce I and another complex which is probably Bi(Rf)Cl2.

Rhodium(I) catalyzed decomposition of formic acid

Abstract Rh(C 6 H 4 PPh 2 )(PPh 3 ) 2 catalyzes the decomposition of formic acid to CO 2 and H 2 . The initial step is the oxidative addition of formic acid to produce the intermediate Rh(HCO 2 )(PPh 3 ) 3 , which probably is followed by β-hydride elimination, to produce CO 2 and RhH(PPh 3 ) 3 . The latter reacts with formic acid to produce H 2 and to reform Rh(HCO 2 )(PPh 3 ) 3 .

Synthesis, characterization and cytotoxicity of new platinum(IV) axial carboxylate complexes: crystal structure of potential antitumor agent [PtIV(trans-1R,2R-diaminocyclohexane)trans(acetate)2Cl2]

A series of new platinum(IV) complexes of the type [PtIV(DACH)trans(L)2Cl2] (where DACH = trans-1R,2R-diaminocyclohexane, and L = acetate, propionate, butyrate, valerate, hexanoate, or heptanoate) bearing the carboxylate groups in the axial positions have been synthesized and characterized by elemental analysis, IR, and 195Pt NMR spectroscopy. The crystal structure of the analogue [PtIV(DACH)trans(acetate)2Cl2] was determined by single crystal X-ray diffraction method. There were two crystallographically independent molecules, both of which lie on crystallographic two-fold axes. The bond lengths and bond angles of both the molecules were the same within the experimental error. The compound crystallizes in the monoclinic space group C2, with a = 11.180(2) A, b = 14.736(3) A, c = 10.644(2) A, beta = 112.38(3) degrees, Z = 4 and R = 0.0336, based upon a total of 1648 collected reflections. In this complex, the platinum had a slightly distorted octahedron geometry owing to the presence of a geometrically strained five-member ring. The two adjacent corners of the platinum plane were occupied by the two amino nitrogens of DACH, whereas the other two equatorial positions were occupied by two chloride ions. The remaining two axial positions were occupied by the oxygens of acetate ligands. The DACH ring was in a chair configuration. An intricate network of intermolecular hydrogen bonds held the crystal lattice together. These analogues were evaluated in vitro and demonstrated cytotoxic activity against the human ovarian 2008 tumor cell line (IC50 = 0.001-0.06 microM). Structure-activity study revealed that activity was highest for the analogue where L = butyrate.

Synthesis, characterization, and antitumor activity of new platinum(IV) trans-carboxylate complexes: Crystal structure of [Pt(cis-1,4-DACH)trans-(acetate)2Cl2]

A series of novel platinum(IV) cisplatin analogues of the type [Pt(cis-1,4-DACH)trans-(L)2Cl2] (where cis-1,4-DACH = cis-1,4-diaminocyclohexane and L = acetate, propionate, butyrate, valerate, hexanoate, heptanoate, octanoate, nonanoate, or decanoate) was synthesized and characterized by elemental analysis, IR, 13C-NMR, and 195Pt-NMR spectroscopy. The structure of [Pt(cis-1,4-DACH)trans-(acetate)2Cl2] (1) was determined by X-ray crystallography. The crystals were monoclinic, space group P2(1)/n (no. 14) with a = 10.193(2), b = 10.687(2), c = 14.265(3) A, beta = 99.67(3) degrees, Z = 4. The total reflections collected were 2556. The structure refinement converged to R1 = 0.0539 and wR2 = 0.1531. In this complex, platinum has distorted octahedral geometry, and cis-1,4-DACH is in a unique twist-boat configuration. cis-1,4-DACH forms a seven-member chelating ring with platinum, leading to considerable strain in bidentate DACH binding. The strain is evidenced by a large 126.5(9) degrees C-N-Pt angle. The N-Pt-N angle is expanded to 97.4(5) degrees owing to geometric constraints of the cis-1,4-DACH geometry. Three lower homologs of the cis-1,4-DACH-Pt(IV) series were tested in the murine L1210/0 leukemia model for antitumor activity. The results indicate that activity decreases in ascending the homologous series, and that the activity of two of the complexes is substantially better than that of cisplatin with respect to increase in life span and cures.

Synthesis and x-ray crystallographic characterization of (μ3-Bi)2Fe3(CO)9: A reformulation of Hieber's Bi2Fe5(CO)20

Abstract When [HFe(CO) 4 ] − is treated first with NaBiO 3 and then dilute H 2 SO 4 , a complex mixture of neutral metal carbonyl clusters results, some of which can be extracted into petroleum ether. Upon prolonged standing the extract yields a precipitate which has been characterized by X-ray crystallography as Bi 2 Fe 3 (CO) 9 . The complex Bi 2 Fe 3 (CO) 9 crystallizes in the centrosymmetric orthorhombic space group Cmcm ( D 2 h 17 ; No. 63) with a 10.616(2) A, b 13.458(3) A, c 11.347(3) A, V 1621.1(7) A 3 and Z = 4. Single-crystal X-ray diffraction data (Mo- K α , 2θ = 4.5–55.0°) were collected on a Syntex P2 1 four-circle diffractometer and the structure was refined to R F 5.4% and R W F 4.5% for all 1039 independent data ( R F 4.5% and R W F 4.5% for those 851 reflections with | F 0 | > 3.0σ(| F 0 |)). The molecule lies on a site of crystallographic C 2 v symmetry and is disordered. The individual molecules have a trigonal bipyramidal Bi 2 Fe 3 core with the bismuth atoms occupying the apical sites (BiFe 2.617(2)–2.643(2) A, FeFe 2.735(5)–2.757(5) A). Each iron atom is linked to three terminal carbonyl ligands and the molecule has approximate C 3 h symmetry. The nine peripheral oxygen atoms are ordered and define a tricapped trigonal prism. The equatorial iron atoms are disordered with the two Fe 3 triangles mutually displaced by approximately 30°; the disordered ensemble has approximate D 3 h symmetry.

Preparation, characterization, and antitumor activity of new cisplatin analogs with homopiperazines: crystal structure of [PtII(1-methylhomopiperazine)(methylmalonato)].2H2O.

A series of new platinum(II) and (IV) complexes with homopiperazine have been synthesized and characterized by elemental analysis, infrared, and 195Pt nuclear magnetic resonance spectroscopic techniques. The complexes are of two types: [PtIILX] (where L = homopiperazine (hpip), 1-methylhomopiperazine (mhpip), or 1,4-dimethylhomopiperazine (dmhpip), and X = 1,1-cyclobutanedicarboxylato (CBDCA), or methylmalonato ligand) and [PtIV(L-)trans-(Y)2Cl2] (where Y = hydroxo, acetato, or chloro ligand). Among the complexes synthesized, the crystal structure of [PtII(mhpip)(methylmalonato)].2H2O was determined by the single crystal X-ray diffraction method. The crystallographic parameters were orthorhombic, P2(1)2(1)2(1) (no. 19), a = 7.2014(14), b = 7.3348(15), c = 26.971(5) A, and Z = 4. The structure refinements converged to R1 = 0.0641 and wR2 = 0.1847. In this complex, platinum has a slightly distorted square planar geometry with the two adjacent corners being occupied by two nitrogens of the mhpip ligand, whereas the remaining cis positions are coordinated with two oxygen atoms of the methylmalonato group. The mhpip ligand is in a boat conformation and forms five and six membered chelating rings with platinum. The intricate network of intermolecular hydrogen bonds holds the crystal lattice together. Some of these synthesized cisplatin analogs have good in vitro cytotoxic activity against the cisplatin-sensitive human ovarian A2780 (IC50 = 0.083-17.8 microM) and the isogenic cisplatin-resistant 2780CP (IC50 = 20.1-118.1 microM) cell lines.

Triethanolamine complexes of copper

Abstract A simple benchtop synthesis of the deep blue tetrameric compound [Cu{N(CH2CH2O)3H}]4 prepared from CuSO4·5H2O and triethanolamine is presented. The compound has been characterized in three different crystalline modifications which vary due to the presence of different lattice solvents that include THF, Et2O and H2O. The compound dissolves in water, alcohols and to a slight extent in dichloromethane and chloroform. It produces basic solutions (Kb=1.2 (±0.4)×10−7) in water and a visible spectrum that varies as a function of pH. FAB mass spectral data indicate that the tetramer remains intact and incorporates additional copper ions in the mass spectrometer.