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PubMed2005

New oxorhenium(V) compound for catalyzed oxygen atom transfer from picoline N-oxide to triarylphosphines.

The synthesis and characterization of a new oxorhenium(V) compound is reported; it is [MeReO(edt)(bpym)], 8, where edt = 1,2-ethanedithiolate and bpym = 2,2'-bipyrimidine. Compound 8 was characterized by NMR spectroscopy and single-crystal X-ray analysis. It exists as a six-coordinate Re(V) compound comparable to the previously known [MeReO(edt)(bpy)] and [MeReO(mtp)(bpy)]. Compound 8 catalyzes the oxygen-atom-transfer reaction PicO + PZ3 --> Pic + Z3PO, whereas the other two do not. The kinetics of this reaction with catalyst 8 follows the rate law -d[PicO]/dt = k[8][PicO]/(1 + c[PZ3]). With different phosphines, the rate law has the same k value, 4.17 L mol(-1) s(-1), but different c values. For tritolylphosphine, c = 67.5 L mol(-1) in benzene at 25 degrees C. A mechanism has been proposed to account for these findings. The data establish that an open coordination site on rhenium is necessary for oxygen-atom-transfer reactions.

Journal Article↗
PubMed1999

Mixed Chloride/Amine Complexes of Dimolybdenum(II,II). 4. Rotational Isomers of Mo(2)Cl(4)(R-py)(4) (R-py = 4-Picoline, 3,5-Lutidine, and 4-tert-Butylpyridine).

The quadruply bonded dimolybdenum complexes with alkyl-substituted pyridines of the formula Mo(2)Cl(4)(R-py)(4) (R-py = 4-pic (4-methylpyridine) (1), 3,5-lut (3,5-dimethylpyridine) (2), and 4-Bu(t)-py (4-tert-butylpyridine) (3)) have been prepared. Nine different compounds, in which there are 11 independent molecules, have been obtained in crystalline form, and their crystal structures have been investigated by X-ray diffraction. Three types of geometric isomers which differ by the angle of internal rotation about the Mo-Mo axis have been recognized in these structures. The eclipsed structures 1-3a display pyridine ligands opposite to each other across the metal-metal bond and have a virtual symmetry D(2)(h)(). The noncentrosymmetric D(2)(d)() structures 1-3b have each pyridine ligand opposite to a Cl atom. The molecules 3c-f have a partially staggered D(2) geometry with N-Mo-Mo-N torsion angles ranging from 10.4 degrees to 25.2 degrees. As a result of this work it is now clear that Mo(2)Cl(4)(R-py)(4) compounds do not show a preference for D(2)(h)() conformation rather than D(2)(d)() conformation. In fact, they seem unusually unrestricted in their rotational conformation, and packing forces appear to have a major influence on the conformation adopted. Further clarification of this question will require spectroscopic study of solutions.

Journal Article↗
PubMed2005

Experimental matrix isolation study and quantum-mechanics-based normal-coordinate analysis of the anharmonic infrared spectrum of picolinic acid N-oxide.

This work is, according to our knowledge, the first experimental matrix isolation study of a molecular system with a very short and strong intramolecular OH...O hydrogen bond. It also includes a satisfying interpretation of its entire infrared spectrum. The interpretation relies on the calculation at the DFT/B3LYP/6-31G(d,p) level of the harmonic spectrum and of the anharmonic relaxed potential energy for the stretching motion of the hydrogen-bonded proton, used with our recently modified quantum-mechanics-based normal-coordinate analysis. An important observation about the anharmonic spectrum obtained from this procedure is that the OH stretch coordinate contributes to several normal modes, mixing extensively with other in-plane internal coordinates, in particular OH-bending and C=O-stretching. The two intense normal modes with the largest contributions from the OH-stretching coordinate to the potential energy distribution and to the intensity are located near 1700 and 1500 cm(-1). A calculated anharmonic spectrum obtained from this procedure agrees with the experimental spectrum (frequencies and intensity distribution), within the limits of the estimated uncertainties for the calculation and experiment, allowing the interpretation of the latter. The agreement for the frequencies is about 1-3%. The anharmonic spectrum calculated using the anharmonic keyword in Gaussian 03w is not in satisfactory agreement with experiment insofar as the OH-stretching mode is concerned.

Journal Article↗
PubMed1996

Synthesis and biological evaluation of 6-(9-hydroxy-5-methyl (and 5,6-dimethyl)-6H-pyrido[4,3-b]carbazol-1-yl)picolinic amides as new olivacine derivatives.

Starting from 2-(6-methoxy-1-methylcarbazol-2-yl)ethylamine and diethyl-2,6-pyridine dicarboxylate, the title compounds were obtained through five or six steps. The new compounds retained significant cytotoxicity towards various tumor cell lines, but in vivo studies on murine P388 leukemia, B16 melanoma and Lewis lung carcinoma showed a lowered antitumor activity with respect to that of the related olivacine lead compound 1.

Animals↗
PubMed1998

Monomeric Three- and Four-Coordinate Magnesium Amides.

Treatment of bis(bis(trimethylsilyl)amido)bis(tetrahydrofuran)magnesium with 2 equiv of 2,3,5-collidine, 2-picoline, 4-picoline, or 3,5-lutidine in benzene at room temperature for 18 h afforded bis(bis(trimethylsilyl)amido)bis(2,3,5-collidine)magnesium (80%), bis(bis(trimethylsilyl)amido)bis(2-picoline)magnesium (70%), bis(bis(trimethylsilyl)amido)bis(4-picoline)magnesium (48%), or bis(bis(trimethylsilyl)amido)bis(3,5-lutidine)magnesium (58%), respectively. Sublimation of bis(bis(trimethylsilyl)amido)bis(2,3,5-collidine)magnesium (90 degrees C, 0.1 mmHg) and bis(bis(trimethylsilyl)amido)bis(2-picoline)magnesium (115 degrees C, 0.1 mmHg) afforded colorless crystals of bis(bis(trimethylsilyl)amido)(2,3,5-collidine)magnesium (53%) and bis(bis(trimethylsilyl)amido)(2-picoline)magnesium (46%), respectively. Treatment of bis(bis(trimethylsilyl)amido)bis(tetrahydrofuran)magnesium with 1 equiv of 2,6-lutidine in benzene at room temperature for 18 h afforded bis(bis(trimethylsilyl)amido)(2,6-lutidine)magnesium (56%). The X-ray crystal structures of bis(bis(trimethylsilyl)amido)bis(2,3,5-collidine)magnesium, bis(bis(trimethylsilyl)amido)bis(4-picoline)magnesium, bis(bis(trimethylsilyl)amido)(2-picoline)magnesium, and bis(bis(trimethylsilyl)amido)(2,6-lutidine)magnesium were determined. Bis(bis(trimethylsilyl)amido)bis(2,3,5-collidine)magnesium crystallizes in the monoclinic space group C2/c with a = 11.8410(7) Å, b = 20.5413(13) Å, c = 15.5746(10) Å, beta = 93.072(2) degrees, V = 3782.8(4) Å(3), and Z = 4. Bis(bis(trimethylsilyl)amido)bis(4-picoline)magnesium crystallizes in the triclinic space group P&onemacr; with a = 10.4914(6) Å, b = 11.8504(6) Å, c = 15.4546(9) Å, alpha = 99.3180(10) degrees, beta = 98.4180(10) degrees, gamma = 111.5320(10) degrees, V = 1718.8(2) Å(3), and Z = 2. Bis(bis(trimethylsilyl)amido)(2-picoline)magnesium crystallizes in the orthorhombic space group Pbca with a = 18.4536(14) Å, b = 15.2326(9) Å, c = 20.614(2) Å, V = 5794.6(7) Å(3), and Z = 8. Bis(bis(trimethylsilyl)amido)(2,6-lutidine)magnesium crystallizes in the orthorombic space group Pbca with a = 18.6221(13) Å, b = 15.3236(9) Å, c = 20.9085(14) Å, V = 5966.4(7) Å(3), and Z = 8. Application of the these complexes as source compounds in chemical vapor deposition processes is discussed.

Journal Article↗
PubMed2006

Novel transplatinum(II) complexes with [N2O2] donor sets. Cellular pharmacology and apoptosis induction in Pam 212-ras cells.

Cellular pharmacological properties of eight trans-picoline platinum(II) complexes of formula trans-[PtX(2)(L)(L')], where X = Cl or CH(3)COO (OAc) and L = L' = 3-picoline (3-pic), 4-picoline (4-pic) or L = NH(3) and L' = 3-pic or 4-pic, were investigated in murine keratinocyte Pam 212 cells and Pam 212-ras cells, murine tumor keratinocytes derived from transformation with a viral vector containing the H-ras oncogene. The derivatives trans-[Pt(OAc)(2)(L)(L')] (L = L' = 3-pic, 9, and L = L' = 4-pic, 10) were able to circumvent resistance in Pam 212-ras cells. Although all the trans-picoline platinum(II) acetate derivatives showed a similar level of DNA binding, there were remarkable differences in cellular accumulation: the complexes having two picoline ligands (9, 10) had a much higher intracellular accumulation than those having mixed picoline and ammine ligands (11, 12). No significant differences in cellular pharmacological properties have been observed between isomers having 3- or 4-picoline.

Animals↗