Synthesis of bis(tert-butyl)cyclopentadienyl derivatives of titanium and zirconium. NMR spectra and dynamic behavior of the base-free [Zr(1,3-tBu2-µ5-C5H3)(CH2Ph)2]+ cation

Reaction of Si(1,3-tBu2-C5H3)Me3 with MCl4 (M = Ti, Zr) in toluene or hexane at room temp. affords the new trichloromonociclopentadienyl-type derivs. [M(1,3-tBu2-η5-C5H3)Cl3] [M = Ti (2), Zr (3)]. Treatment of complexes 2 and 3 with appropriate alkylating reagents in hexane gives the 1,3-di(tert-butyl)cyclopentadienyl trialkyl titanium and zirconium complexes [M(1,3-tBu2-η5-C5H3)R3] [M = Ti, R = CH3, CH2Ph; M = Zr, R = CH3, CH2Ph (7), CH2CMe2Ph]. Interestingly, when 2 reacts with 3.1 equiv of LiCH2CMe2Ph in hexane at room temp. the ring-tert-butyl-metalated complex [Ti(1-tBu-3-CMe2CH2-η5-C5H3) (CH2CMe2Ph)2] was isolated in 90% yield. The cationic mono(1,3-di-(tert-butyl)cyclopentadienyl) dibenzyl zirconium species [Zr(1,3-tBu2-η5-C5H3)(CH2Ph)2]+, generated in situ by reaction of the tribenzyl complex 7 with B(C6F5)3 or [CPh3]+[B(C6F5)4]- reagents, is reported and their dynamic NMR behavior in CD2Cl2 solns. at low temps. is studied.Financial support for this research by DGICYT (Project\ud PB92-0178-C) is gratefully acknowledged. J.I.A.\ud acknowledges Repsol Petróleo S.A. for a fellowship

Synthesis and characterization of new alkoxide and aryloxide derivatives of titanium and zirconium. X-ray molecular structure of [ZrCp2(OC6F5)2]

Lithium or sodium alkoxides MOR (R double bond; length as m-dashCH2CHdouble bond; length as m-dashCMe2; M double bond; length as m-dash Li1; Na2; R double bond; length as m-dash C6F5; M double bond; length as m-dash Li3 were prepared by reaction of the alcohols with n-butyl lithium or sodium metal in hexane. Reaction of a hexane suspension of3 with SiClMe, afforded SiMe3(OC6F5)4, whereas the reaction of 3 equivalents of C6F5OH with AlMe3 in hexane led to Al(OC6F5)35. Compounds1 or2 react with one equivalent of [TiCp*Cl2Me] (Cp*double bond; length as m-dash C5Me5) in toluene to give [TiCp*ClMe(OCH2CHdouble bond; length as m-dashCMe2)]6. Complex6 reacts with AlEtCl2 to give quantitatively [TiCp*Cl3]. In the presence of water, the hydrolysis of6 takes palce giving the μ-oxo compound [{(TiCp*Cl)(μ − O)}3]. [TiCp*Cl2Me] reacted with an excess of the alcohol C6F5OH to give [TiCp*(OC6F5)3]7. [ZrCp2Cl2] reacted with two equivalents of pentaflurophenol in the presence of aniline to give the dialkoxide [ZrCp2(OC6F5)2]8. When the same reaction was carried out in a 1:1 molar ratio, a mixture of8 and the chloroalkoxide [ZrCp2Cl(OC6F5)]9 was obtained. A cleac reaction takes place when the μ-oxo compound [(ZrCp2Me)2(μ-O)] is treated with two equivalents of pentaflurophenol, leading to the isolation of the alkoxo complex [{ZrCp2(OC6F5)}2(μ-O)]10. The methylalkoxo derivative [ZrCp2Me(OC6F5)]11, was obtained by rection of [ZrCp2ClMe] with one equivalent of3. Alternative methods can be also be followed to synthesize8 and11. The crystal and molecular structure of8 has been determined by X-ray diffraction methods. The most interesting feature of this structure is the disposition of the (C6F5) ring planes, which are located practically on the reflection plane defined by O(1), Zr(1) and O(1)′

Neutral and cationic di(tert-butyl) cyclopentadienyl titanium, zirconium and hafnium complexes. Dynamic NMR study of the ligand-free cations [M(1,3-tBu2-η5-C5H3)(η5-f5H5)(CH3)]+(M=Zr, Hf)

Group 4 metal complexes containing the di(tert-butyl)cyclopentadienyl ligand (l,3-tBu2-r/5-CsH3) have been synthesized. The\ud reaction of a mixture of 1,3- and 1,4-di(tert-butyl)cyclopentadiene isomers with KH in THF at -78°C gives the salt K+[(1,3 -\ud tBu2CsH3)]-(THF)I_3 2 as a white solid. Treatment of 2 with chlorotrimethylsilane in a 1:1 molar ratio gives the air-stable\ud trimethylsilylcyclopentadienyl derivative Si(1,3-tBu2C5H3XCH3)3 3. The silyl derivative 3 is an excellent precursor for monocyclopentadienyl\ud trichlorotitanium and zirconium compounds M(1,3 -t Bu 2-r/5-C 5 H 3)C13 [M = Ti (4), Zr (5)]. Addition of a stoichiometric amount\ud of water in the presence of NEt 3 to a toluene solution of 4 affords the oxo trimer compound [Ti(1,3-tBu2-~75 - CsH3)CI( p,-O)] 3 6. The\ud reaction of 4 with 2 equiv, of LiMe affords the chloro dimethyl derivative Ti(1,3-tBu2-'r/5-CsH3)CI(CH3)2 7. The mixed dicyclopentadienyl\ud compounds M(1,3-tBu2-r/5-CsH3XCsHs)CI2 [M = Ti (8); Zr (9)] were prepared by reaction of complexes 4 and 5 respectively with\ud TI(CsHs). Treatment of complexes (8) and (9) with the appropriate alkylating reagent and molar ratio, in hexane at -78 °C, gives the\ud chloro alkyl derivatives M(1,3-tBu2-@-C5H3XCsHs)CIR [M = Ti, R = Me (10); M = Zr, R = Me (11), Bz (12)] or the dialkyl\ud complexes M(1,3-tBu2-@-CsH3)(CsHs)Rz [M = Ti, R = Me (13); M = Zr, R = Me (14), Bz (15), Nf (16)]. When 8 reacts with 2 equiv.\ud of MgBz2(THF) 2 or LiCH2CMe2Ph the metallacyclic complexes Ti(1-tBu-3-CMe2CH~-r/5-C~Ha)(CsHs)R [R = Bz (17); Nf (18)] were\ud isolated as red oils at room temperature, with the elimination of toluene or ten-butyl benzene respectively. The previously reported\ud cationic mono 1,3-di(tert-butyl)cyclopentadienyl dibenzyl zirconium species [Zr(1,3 -t Bu 2-'05-C 5 H 3 XCH 2 Ph) 2 ] + (19) can be stabilized\ud by reaction with tBuNC or PMe 3, in CD2C12 at -78°C, and the formation of the new cationic species [Zr(1,3-tBu2-r/5-\ud CsHa)(L)(CH2Ph)2] + [L=tBuNC (20); PMe 3 (21)] was identified by NMR spectroscopy. The reaction of B(CrFs) 3 with the\ud monocyclopentadienyl trimethyl derivatives M(1,3-tBu2-r/5-CsH3XCH3)3 [M = Ti (22), Zr (23)], in the presence of PMe 3, gives the\ud cationic species [M(I,3-tBu2-@-C~H3)(PMe3)2(CH3)2] + [M = Ti (24); Zr (25)], obtained as orange-yellow solids, stable at room\ud temperature. The reaction of B(C6Fs) 3 with the metallocene dimethyl derivatives M(1,3-tBu2-r/5-CsHa)(@-CsHs)(CH3)z [M = Zr (14);\ud Hf (26)], in a 1:1 molar ratio and in hydrocarbon solvents gives the cationic derivatives [M(1,3-tBu2-@-CsH3)(@ -\ud CsHsXCH3)]+[(CH3)B(CrFs)3] - [M = Zr (27); Hf (28)] as yellow oils which can be stored for weeks under an inert atmosphere. When\ud the same reactions of (14) and (26) with B(C6Fs) 3 are carried out in a 2:1 molar ratio at room temperature, the complexes\ud {[M(1,3-tBu2-@-CsH3X@-CsH5)Me]2(/.L-Me)}[MeB(C6Fs)3] [M =Zr (29), Hf (30)] can be obtained as a mixture of syn- and\ud anti-isomers as shown by NMR spectroscopic observations. The formation of (29) and (30) implies the stabilization of the 14-electron\ud cationic intermediate by interaction with one methyl group of the neutral complexes (14) and (26). Complexes (27) and (28) undergo\ud heterolytic dissociation of the Metal-MeB(C6Fs) 3 bonds, leading to the formation of the free [M(I,3-tBu2-r/5-CsH3)(r/5-CsHs)(CH3)] +\ud 14-electron species, verified by 1H DNMR spectroscopy. When compound (27) was heated at 50°C the metallacyclic cation\ud [Zr(1-tBu-3-CMezCH2-@-C5H3)(@-CsHs)] + (31) was formed. The alkyl derivatives synthesized and reported herein, activated with MAO, B(C6Fs) 3 or [Ph3C][B(C6Fs)4], polymerize ethylene with very low activity. The molecular structure of [Ti(1,3-tBu2-r/5-\ud C5H3)C1(/x-O)] 3 6 has been determined by X-ray diffraction methods.Financial support for this research by DGICYT (Project PB92-0178C) is gratefully acknowledged. J.I.A.\ud acknowledges Repsol Petróleo S.A. for a fellowship. A.M. is grateful to Consejeria Educaci6n (CAM) for a fellowship

Study of the anticancer properties of optically active titanocene oximato compounds

New water soluble and optically active cyclopentadienyl titanium derivatives [(η5-C5H5)2Ti{(1R,4S)-ĸON,(R)NH}Cl] (R = Bn (Benzyl) 1a’, 2-pic (2-picolylamine) 1b’) have been synthesized. The novel compounds along with those previously described [(η5-C5H5)2Ti{(1S,4R)-ĸON,(R)NH}Cl] (R = Bn 1a, 2-pic 1b) were evaluated by polarimetry, ultra-violet and circular dichroism spectroscopy. The structure of 1b was determined by single crystal X-ray crystallography and showed a unique terminal monohapto Tisingle bondO disposition of the oximato ligand. All enantiomers have been tested against several cancer cell lines in vitro: prostate PC-3 and DU-145, lung A-549, pancreas MiaPaca-2, colorectal HCT-116, leukemia Jurkat and cervical HeLa. In addition, 1a, 1b and 1b’ were tested against non-tumorigenic prostate RWPE-1 cell line. After 24 h of incubation, 1b and 1b’ were moderately active against Jurkat and A-549 cells. The anti-proliferative effect of titanium compounds on prostate PC-3, DU-145 and RWPE-1 cell lines was also assessed after 72 h of drug exposure. The cytotoxic profile of the enantiomers was similar, exception made for the PC-3 cells, with S,R-isomers exhibiting cytotoxicities 2 to 3 times higher than R,S-compounds. Under these conditions, derivative 1b showed calculated IC50 values better than those of Tacke's Titanocene-Y (bis-[(p-methoxybenzyl)cyclopentadienyl]titanium(IV) dichloride) on both the prostate PC-3 and DU-145 cells. 1a and 1b cytotoxic behaviour shows certain selectiveness, with activities 2–4 times lower on normal prostate RWPE-1 than on cancer PC-3 cells. Furthermore, 1b produces higher cytotoxicity on prostate PC-3, DU-145 and RWPE-1 cells than the additive dose of titanocene dichloride and pro-ligand b·HCl. Additionally, compound-DNA interactions have been investigated by equilibrium dialysis, Fluorescence Resonance Energy Transfer (FRET) melting assays and viscometric titrations, which suggest that these metal complexes and/or their hydrolysis products bind DNA either in the minor groove or externally.Ministerio de Economía y CompetitividadComunidad Autónoma de MadridUniversidad de Alcal

Ring-Opening Polymerization of L-Lactide Catalyzed by Potassium-Based Complexes: Mechanistic Studies

Two non-toxic potassium compounds, 1 and 2, with a commercial oximate ligand have been prepared and fully spectroscopically characterized. Their activity as catalysts for the ring-opening polymerization (ROP) process of LLA has been studied, showing that they are extremely active and able to polymerize the monomer in a few minutes. For derivative 2, the presence of a crown ether in the potassium coordination sphere affects the nuclearity of the compound and consequently its solubility, with both aspects having an influence in the polymerization process. Detailed studies of the polymerization mechanism have been performed, and an unusual anionic mechanism was observed in absence of a co-initiator. Indeed, the monomer deprotonation generates a lactide enolate, which initiates the polymerization propagation. On the contrary, when a 1:1 ratio of cat:BnOH is used, a mixture of mechanisms is observed, the anionic mechanism and the activated monomer one, while from a cat:BnOH ratio of 1:2 and over, only the activated monomer mechanism is observed

Insertion of isocyanides into zirconium-alkyl bonds of di-ansa-zirconocene complexes. X-ray molecular structure of [Zr{(SiMe2)2(η5-C5H3))Cl(η2-C(i-Pr)N(2,6-Me2C6H3)}]

New dicyclopentadienyl iminoacyl zirconium complexes have been prepared and characterized by NMR spectroscopy. The reaction of [Zr{SiMe2)2(η5-C5H3)2)Me2] with CNR (R  2,6-Me2C6H3, t-Bu) yields [Zr((SiMe2)2(η5-C5H3)2Me(η2-CMeNR)] (R = 2,6-Me2C6H3, t-Bu), which reacts with a stoichiometric amount of water to give the μ-oxo dimers [Zr{(SiMe2)2(η5-C5H3)2}(η2-CMeNR)]2(μ-O) (R = 2,6-Me2C6H3, t-Bu). The chloro neophyl complex [Zr{(SiMe2)2(η5-C5H3)2}Cl(CH2CMe2Ph)] and other β-hydrogen containing zirconium chloro alkyls [Zr{(SiMe2)2(η5-C5H3)2}CIR] (R  Et, n-Pr, i-Pr)_ with CN(2,6-Me2C6H3) to yield the related chloro iminoacyl complexes [Zr{(SiMe2)2(η5-C5H3)2)Cl}η2-CRN(2,6-Me2C6H3)}] (R  Et, n-Pr, i-Pr), whereas no reaction was observed when CN(t-Bu) was used. All the new iminoacyl complexes were characterized by 1H and 13C NMR spectroscopy and the X-ray molecular structure of [Zr{(SiMe2)2(η5-C5H3)2)Cl{η2-C(i-Pr)N(2,6-Me2C6H3)}] studied by diffraction methods to prove the expected ‘inside’ coordination of the iminoacyl nitrogen atom.BID-CONICIT (Venezuela)Comunidad Autónoma de Madri

Water soluble, optically active monofunctional Pd(II) and Pt(II) compounds: promising adhesive and antimigratory effects on human prostate PC-3 cancer cells

New water soluble, enantiopure palladium and platinum compounds R-N-[M{(1S, 4R)-kappa NOH,kappa(NH)-N-2(2-pic)} Cl]Cl and S-N-[M{(1R, 4S)-kappa NOH,kappa(NH)-N-2(2-pic)}Cl]Cl (2-pic = 2-picolyl, M = Pd 1 and 1', Pt 2 and 2', respectively), and heterometallic Pd/Ti [(eta(5)-C5H5)(2)Ti{(1S, 4R)-kappa ON,kappa(NH)-N-2(2-pic)}(PdCl)] Cl (3) have been synthesized. These novel compounds were fully characterized by NMR spectroscopy and CHN elemental analysis and 1, 1', 2 and 2' were further evaluated by polarimetry, ultra-violet and circular dichroism spectroscopy. The aqueous stability of novel compounds was studied by NMR spectroscopy under physiological conditions and the new species detected under such conditions have been characterized by NMR techniques and HR-ESI-MS (High-Resolution Electrospray Ionization Mass Spectrometry). CompoundDNA interactions have been investigated for the palladium and platinum compounds by equilibrium dialysis, Fluorescence Resonance Energy Transfer (FRET) DNA melting assays and viscometric titrations, revealing a better binding affinity and ability to affect duplex DNA of the palladium compounds. Metal derivatives have been tested in vitro against three cancer (prostate PC-3, cervical HeLa and breast MCF-7) and one non-tumorigenic (human prostate RWPE-1) cell lines. The highest anticancer activities were shown by palladium compounds 1 and 1' in all cancer lines, although their toxicity was lower than that found for cisplatin. Most importantly, the effect of the compounds on the cell adhesion and migration of the androgen- independent prostate cancer PC-3 cells has been assessed, and the efficacy of Pd enantiomers to affect the invasive phenotype of PC-3 cells has been demonstrated.Universidad de AlcaláComunidad de Madri

Stereoselective synthesis of oxime containing Pd(II) compounds: Highly effective, selective and stereo-regulated cytotoxicity against carcinogenic PC-3 cells

New palladium compounds [Pd{(1S,4R)-NOHNH(R)}Cl-2] (R = Ph 1a or Bn 1b), [Pd{(1S,4R)-NOHNH(R)}{(1S,4R)-NONH(R)}][Cl] (R = Ph 2a or Bn 2b) and corresponding [Pd{(1R,4S)-NOHNH(R)}Cl-2] (R = Ph 1a' or Bn 1b') and [Pd{(1R,4S)-NOHNH(R)}{(1R,4S)-NONH(R)}][Cl] (R = Ph 2a' or Bn 2b') have been synthesized. Novel compounds 1a, 1b, and 2b (and 1a', 1b', and 2b') were obtained in solution as a mixture of diastereomers whose relative ratios depend on the solvent and the nature of the amino substituent. In contrast, the synthetic reactions of derivatives 2a and 2a' were stereospecific, and afforded single enantiomers of absolute configuration (S-N,1S(C),4R(C))-(R-N,1S(C),4R(C)) and (R-N,1R(C),4S(C))-(S-N,1R(C),4S(C)), respectively. All compounds have been fully characterized by NMR and IR spectroscopy, time-dependent UV-spectroscopy, ESI-HR-MS in water, and CHN elemental analysis. Absolute configurations of the major epimers of 1a and 1a', both epimers of 1b and enantiomer 2a', were determined by single crystal X-ray crystallography, and confirmed by 2D NOESY NMR experiments in solution. Additionally, the pH-dependent stability of 2b in water was assessed by H-1-NMR spectroscopy. Metal derivatives have been tested in vitro against three human cancer (prostate PC-3, cervical HeLa, and breast MCF-7) cell lines. The highest anticancer activities were shown by palladium compound 2a' in all cancer cells, with IC50 values up to 80 times lower than those found for cisplatin. The cytotoxicity of 2a and 2a '' is stereo-dependent, with IC50 values that differ significantly for each enantiomer in all the cell lines tested. The cytotoxic activity of 2a and 2a' was further evaluated against the non-tumorigenic human prostate RWPE-1 cell line, revealing a selectivity index (SI) of ca. 30 for derivative 2a'. DNA interactions have been investigated by equilibrium dialysis, fluorescence resonance energy transfer (FRET) DNA melting assays, and viscometric titrations, pointing to groove and/or external binding. Cell cycle assay on PC-3 cells after treatment with 2a or 2a' shows cell cycle arrest in the S and G2/M phases, especially when the cells are treated with compound 2a'.Ministerio de Ciencia e InnovaciónMinisterio de Economía, Industria y CompetitividadUniversidad de AlcaláComunidad de Madri

Biological evaluation of water soluble arene Ru(II) enantiomers with amino-oxime ligands

New water soluble, enantiopure arene ruthenium compound SRuSN-(1R,4S)-[(η6-p-cymene)Ru{ĸNH(Bn),ĸNOH}Cl]Cl (Bn = benzyl, 1a′) has been synthesized. The novel compound along with that previously described RRuRN-(1S,4R)-[(η6-p-cymene)Ru{ĸNH(Bn),ĸNOH}Cl]Cl (1a) was evaluated by polarimetry, ultra-violet and circular dichroism spectroscopy. The structure of novel ruthenium derivative 1a′ was determined by single crystal X-ray crystallography. Both enantiomers have been tested against several cancer cell lines in vitro: prostate PC-3, lung A-549, pancreas MIA PaCa-2, colorectal HCT-116, leukemia Jurkat and cervical HeLa. Both enantiomers are active and versatile cytotoxic agents, showing IC50 values from 2 to 12 times lower than those found for cisplatin in the different cell lines evaluated. The mechanism of cell death induced by the metal compounds was analyzed in A-549 and Jurkat cell lines. Derivatives 1a and 1a′ induced apoptotic cell death of A-549 cells while dose-dependent cell death mechanisms have been found in the Jurkat cell line. Compound-DNA interactions have been investigated by equilibrium dialysis, Fluorescence Resonance Energy Transfer (FRET) melting assays and viscometric titrations, revealing moderate binding affinity of 1a and 1a′ towards duplex DNA. Finally, the efficacy of 1a in a preliminary in vivo assay of PC-3 xenografts in nude mice has been evaluated, resulting in a promising inhibition of tumor growth by 45%. Analysis of tumor tissue also showed a significant decrease of levels of crucial molecules in the invasive phenotype of PC-3 cells.Ministerio de Economía y CompetitividadComunidad Autónoma de MadridUniversidad de Alcal