Half-sandwich titanium(IV) complexes with Kläui's tripod ligand

Treatment of [Ti(O-i-Pr)(2)Cl(2)] with NaL(OEt) (L(OEt)(-) = [CpCo[P(O)(OEt)(2)](3)](-), Cp = eta(5)-C(5)H(5)) afforded [L(OEt)Ti(O-i-Pr)(2)Cl] that reacted with HCl in ether to give [L(OEt)TiCl(3)] (1). The average Ti-O and Ti-Cl distances in 1 are 1.975 and 2.293 A, respectively. Reaction of titanyl sulfate with NaL(OEt) in water followed by addition of HBF(4) afforded [L(OEt)TiF(3)] (2), the Ti-O and Ti-F distances of which are 2.020(2) and 1.792(2) A, respectively. The Zr(IV) analogue [L(OEt)ZrF(3)] (3) was prepared similarly from zirconyl nitrate, NaL(Oet), and HBF(4) in water. The Zr-O and average Zr-F distances in 3 are 2.139(2) and 1.938(2) A, respectively. Treatment of 1 with tetrachlorocatechol (H(2)Cl(4)cat) afforded [L(OEt)Ti(Cl(4)cat)Cl] (4). The average Ti-O(P), Ti-O(C), and Ti-Cl distances in 4 are 1.972, 1.926, and 2.334 A, respectively. Hydrolysis of 4 in the presence of Et(3)N yielded the mu-oxo dimer [(L(OEt))(2)Ti(2)(Cl(4)cat)(2)(mu-O)] (5). The average Ti-O(P), Ti-O(C), and Ti-O(Ti) distances in 5 are 2.027, 1.926, and 1.7977(9) A. Treatment of 1 with 1,1'-binaphthol (BINOLH(2)) in the presence of Et(3)N afforded [(L(OEt))(2)Ti(2)(mu-O)(2)(mu-BINOL)] x 2BINOLH(2) (6.2BINOLH(2)). Complex 1 is capable of catalyzing ring opening of epoxides with Me(3)SiN(3) under solvent-free conditions presumably via a Ti-azide intermediate.     

Detection of Anti-Ulcer Drugs and Their Metabolites in Horse Urine by Liquid Chromatography – Mass Spectrometry

This paper describes a convenient method for the extraction and detection of eight anti-ulcer drugs simultaneously in horse urine, a relatively complex and viscous matrix, using a single-step liquid-liquid extraction followed by high-performance liquid chromatography – mass spectrometry (LC-MS). Anti-ulcer drugs were isolated from horse urine by salting out and liquid-liquid extraction. Detection of these drugs at concentrations below 1 ng mL^?1 could be achieved using LC-MS-MS in the positive atmospheric pressure chemical ionisation (APCI) mode. The above analysis was also extended to elimination studies of horses administered with ranitidine and omeprazole. The urinary elimination data of these two drugs suggest that ranitidine was eliminated from horse urine at a much slower rate than omeprazole. In addition, three ranitidine metabolites and six omeprazole metabolites were identified for the first time in equine urine samples.     

Nuclear quadrupole hyperfine structure in the microwave spectrum of HCl-N2O: electric field gradient perturbation of N2O by HCl

The microwave spectra of six isotopomers of HCl-N(2)O have been obtained in the 7-19 GHz region with a pulsed molecular beam, Fourier transform microwave spectrometer. The nuclear quadrupole hyperfine structure due to all quadrupolar nuclei is resolved and the spectra are analyzed using the Watson S-reduced Hamiltonian with the inclusion of nuclear quadrupole coupling interactions. The spectroscopic constants determined include rotational constants, quartic and sextic centrifugal distortion constants, and nuclear quadrupole coupling constants for each quadrupolar nucleus. Due to correlations of the structural parameters, the effective structure of the complex cannot be obtained by fitting to the spectroscopic constants of the six isotopomers. Instead, the parameters for each isotopomer are calculated from the A and C rotational constants and the chlorine nuclear quadrupole coupling constant along the a-axis, chi(aa). There are two possible structures; the one in which hydrogen of HCl interacts with the more electronegative oxygen of N(2)O is taken to represent the complex. The two subunits are approximately slipped parallel. For H (35)Cl-(14)N(2)O, the distance between the central nitrogen and chlorine is 3.5153 A and the N(2)O and HCl subunits form angles of 72.30 degrees and 119.44 degrees with this N-Cl axis, respectively. The chlorine and oxygen atoms occupy the opposite, obtuse vertices of the quadrilateral formed by O, central N, Cl, and H. Nuclear quadrupole coupling constants show that while the electric field gradient of the HCl subunit remains essentially unchanged upon complexation, there is electronic rearrangement about the two nitrogen nuclei in N(2)O.     

Enantioselective guest binding and dynamic resolution of cationic ruthenium complexes by a chiral metal-ligand assembly

A supramolecular metal-ligand assembly encapsulates a variety of cationic half-sandwich ruthenium complexes. Due to the chirality of both host and guest, chiral recognition is observed with diastereomeric excesses up to 70%. The chiral cavity can be used to carry out a dynamic resolution of the rapidly equilibrating enantiomers of the chiral organometallic guest.