Phosphato, chromato, and perrhenato complexes of titanium(IV) and zirconium(IV) containing Klaui's tripodal ligand

Treatment of titanyl sulfate in dilute sulfuric acid with 1 equiv of NaLOEt (L-OEt(-) = [(eta(5) -C5H5)Co{P(O)(OEt)(2)}(3)](-)) in the presence of Na3PO4 and Na4P2O7 led to isolation of [(LOEtTi)(3)(mu-O)(3)(mu(3)-PO4)] (1) and [(LOEtTi)(2)(mu-O)(mu-P2O7)1 (2), respectively. The structure of 1 consists of a Ti3O3 core capped by mu(3)-phosphato group. In 2, the [P2O7](4-) ligands binds to the two Ti's in a U:172,171 fashion. Treatment of titanyl sulfate in dilute sulfuric acid with NaLOEt and 1.5 equiv of Na2Cr2O7 gave [(LOEtTi)(2)(mu-CrO4)(3)] (3) that contains two LOEtTi3+ fragments bridged by three mu-CrO42--O,O' ligands. Complex 3 can act as a 6-electron oxidant and oxidize benzyl alcohol to give ca. 3 equiv of benzaldehyde. Treatment of [LOEtTi(OTf)(3)] (OTf- = triflate) with [n-Bu4N][ReO4] afforded [{LOEtTi(ReO4)(2)}(2)(mu-O)] (4). Treatment of [LOEtMF3] (M = Ti and Zr) with 3 equiv of [ReO3(OSiMe3)] afforded [LOEtTi(ReO4)(3)] (5) and [LOEtZr(ReO4)(3)(H2O)] (6), respectively. Treatment of [LOEtMF3] with 2 equiv of [ReO3(OSiMe3)] afforded [LOEtTi(ReO4)(2) (ReO4)(2)F] (7) and [{LOEtZr(ReO4)(2)}(2)(mu-F)(2)] (8), respectively, which reacted with Me3SiOTf to give [LOEtM(ReO4)(2)(OTf)] (M = Ti (9), Zr (10)). Hydrolysis of [LOEtZr(OTf)(3)] (11) with Na(2)WO(4)center dot xH(2)O and wet CH2Cl2 afforded the hydroxo-bridged complexes [{LOEtZr(H2O)}(3)(mu-OH)(3)(mu(3)-O)][OTf](4) (12) and [{LOEtZr(H2O)(2)}(2)(mu-OH)(2)][OTf](4) (13), respectively. The solid-state structures of 1-3, 6, and 11-13 have been established by X-ray crystallography. The LOEtTiIv complexes can catalyze oxidation of methyl p-tolyl sulfide with tert-butyl hydroperoxide. The bimetallic TV Re complexes 5 and 9 were found to be more active catalysts for the sulfide oxidation than other Ti(IV) complexes presumably because Re alkylperoxo species are involved as the reactive intermediates

Half-Sandwich Titanium(IV) Complexes with Klaui's Tripod Ligand

Treatment of [Ti(O-i-Pr)2Cl2] with NaLOEt (LOEt- = [CpCo{P(O)(OEt)2}3]-, Cp = η5-C5H5) afforded [LOEtTi(O-i-Pr)2Cl] that reacted with HCl in ether to give [LOEtTiCl3] (1). The average Ti−O and Ti−Cl distances in 1 are 1.975 and 2.293 Å, respectively. Reaction of titanyl sulfate with NaLOEt in water followed by addition of HBF4 afforded [LOEtTiF3] (2), the Ti−O and Ti−F distances of which are 2.020(2) and 1.792(2) Å, respectively. The Zr(IV) analogue [LOEtZrF3] (3) was prepared similarly from zirconyl nitrate, NaLOet, and HBF4 in water. The Zr−O and average Zr−F distances in 3 are 2.139(2) and 1.938(2) Å, respectively. Treatment of 1 with tetrachlorocatechol (H2Cl4cat) afforded [LOEtTi(Cl4cat)Cl] (4). The average Ti−O(P), Ti−O(C), and Ti−Cl distances in 4 are 1.972, 1.926, and 2.334 Å, respectively. Hydrolysis of 4 in the presence of Et3N yielded the μ-oxo dimer [(LOEt)2Ti2(Cl4cat)2(μ-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) Å. Treatment of 1 with 1,1‘-binaphthol (BINOLH2) in the presence of Et3N afforded [(LOEt)2Ti2(μ-O)2(μ-BINOL)]·2BINOLH2 (6·2BINOLH2). Complex 1 is capable of catalyzing ring opening of epoxides with Me3SiN3 under solvent-free conditions presumably via a Ti−azide intermediate

Titanium(IV) and zirconium(IV) sulfato complexes containing the Klaui tripodal ligand: Molecular models of sulfated metal oxide surfaces

Treatment of titanyl sulfate in about 60 mM sulfuric acid with NaLOEt (L-OEt(-) = [(eta(5)-C5H5)Co{P(O)(OEt)(2)}(3)](-)) afforded the mu-sulfato complex [(LOEtTi)(2)(mu-O)(2)(mu-SO4)] (2). In more concentrated sulfuric acid (>1 M), the same reaction yielded the di-mu-sulfato complex [(LOEtTi)(2)(mu-O)(mu- SO4)(2)] (3). Reaction of 2 with HOTf (OTf=triflate, CF3SO3) gave the tris(triflato) complex [LOEtTi(OTf)(3)] (4), whereas treatment of 2 with Ag(OTf) in CH2Cl2 afforded the sulfato-capped trinuclear complex [{(L-OEt)(3)Ti-3(mu- O)(3)}(mu(3)-SO4){Ag(OTf)}][OTf] (5), in which the Ag(OTf) moiety binds to a mu-oxo group in the T-3(mu-O)(3) core. Reaction of 2 in H2O with Ba(NO3)(2) afforded the tetranuclear complex (L-OEt)(4)Ti-4(mu-O)(6) (6). Treatment of 2 with [{Rh(cod)Cl}(2)] (cod = 1,5-cyclooctadiene), [Re(CO)(5)Cl], and [Ru(tBu(2)bpy)(PPh3)(2)Cl-2] (tBu(2)bpy=4,4'-di-tertbutyl-2,2'-dipyridyl) in the presence of Ag(OTf) afforded the heterometallic complexes [(L-OEt)(2)Ti-2(O)(2)(SO4) {Rh(cod)}(2)][OTf](2) (7), [(L-OEt)(2)Ti(O)(2)- (SO4){Re(CO)(3)}][OTf] (8), and [{(L-OEt)(2)Ti-2(mu-O)} mu(3) - SO4) (mu-O)(2){Ru(PPh3)(tBu(2)bpy)}][OTf](2) (9), respectively. Complex 9 is paramagnetic with a measured magnetic moment of about 2.4 mu(B). Treatment of zirconyl nitrate with NaLOEt in 3.5 M sulfuric acid afforded [(L-OEt)(2)Zr(NO3)][LOEtZr(SO4) (NO3)] (10). Reaction of ZrCl4 in 1.8 M sulfuric acid with NaLOEt in the presence Na2SO4 gave the R-sulfato-bridged complex [LOEtZr(SO4)(H2O)](2)(mu-SO4) (11). Treatment of 11 with triflic acid afforded [(LOEt)(2)Zr][OTf](2) (12), whereas reaction of 11 with Ag(OTf) afforded a mixture of 12 and trinuclear [{LOEtZr(SO4)(H2O)}(3)(mu-SO4)][OTf] (13). The Zr-IV triflato complex [LOEtZr(OTf)(3)] (14) was prepared by reaction of LOEtZrF3 with Me3SiOTf. Complexes 4 and 14 can catalyze the Diels-Alder reaction of 1,3-cyclohexadiene with acrolein in good selectivity. Complexes 2-5, 9-11, and 13 have been characterized by X-ray crystallography

Lovastatin for the Treatment of Adult Patients With Dengue: A Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND: Dengue endangers billions of people in the tropical world, yet no therapeutic is currently available. In part, the severe manifestations of dengue reflect inflammatory processes affecting the vascular endothelium. In addition to lipid lowering, statins have pleiotropic effects that improve endothelial function, and epidemiological studies suggest that outcomes from a range of acute inflammatory syndromes are improved in patients already on statin therapy. METHODS: Following satisfactory review of a short pilot phase (40 mg lovastatin vs placebo in 30 cases), we performed a randomized, double-blind, placebo-controlled trial of 5 days of 80 mg lovastatin vs placebo in 300 Vietnamese adults with a positive dengue NS1 rapid test presenting within 72 hours of fever onset. The primary outcome was safety. Secondary outcomes included comparisons of disease progression rates, fever clearance times, and measures of plasma viremia and quality of life between the treatment arms. RESULTS: Adverse events occurred with similar frequency in both groups (97/151 [64%] placebo vs 82/149 [55%] lovastatin; P = .13), and were in keeping with the characteristic clinical and laboratory features of acute dengue. We also observed no difference in serious adverse events or any of the secondary outcome measures. CONCLUSIONS: We found lovastatin to be safe and well tolerated in adults with dengue. However, although the study was not powered to address efficacy, we found no evidence of a beneficial effect on any of the clinical manifestations or on dengue viremia. Continuing established statin therapy in patients who develop dengue is safe.Chinese Clinical Trials Registration. ISRCTN03147572