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PubMed2002

The effect of a Titanocene Dichloride derivative, Ti IV (C5H5)(2) NCS(2), on the haematopoietic response of Ehrlich tumour-bearing mice.

The effects of the [Ti IV (C(5)H(5))(2) NCS(2)] metallocene (BCDT), a Titanocene Dichloride derivative, on the growth and differentiation of granulocyte-macrophage progenitor cells [colony-forming unit-granulocyte-macrophage (CFU-GM)] and bone marrow cellularity in normal and Ehrlich ascites tumour-bearing mice were studied. As expected for the Ehrlich ascites tumour-model, concomitant myelosuppression, increased number of spleen CFU-GM and changes in bone marrow cellularity were observed. The treatment of Ehrlich ascites tumour-bearing mice with BCDT (10-30 mg/kg/day) produced a dose-dependent increase in myelopoiesis, a reduction in splenic colonies and a restoration in the total and differential marrow cell counts. We also observed an increase in CFU-GM number when bone marrow cells obtained from normal mice were incubated in vitro with serum from normal mice treated with BCDT. In addition, BCDT prolonged, in a dose-dependent manner, the survival of mice inoculated with Ehrlich ascites tumour. Although it has been previously reported that substitutions in the two halides of the titanocene do not interfere with antitumoural effect, our results with BCDT demonstrated a reduction in antitumour efficacy when compared to previous results with the original titanocene produced in our laboratory.

Animals↗

PubMed1988

Planar chromatographic separation of enantiomers and diastereomers with cyclodextrin mobile phase additives.

A variety of racemic compounds were resolved using reversed-phase thin-layer chromatography (TLC) with mobile phases containing highly concentration solutions of beta-cyclodextrin (beta-CD). These include the drugs labetalol and mephenytoin, metallocenes, crown ethers, methyl-p-toluenesulfinate, nornicotine derivaties and several dansyl and beta-naphthylamide substituted amino acids. It was possible to resolve some racemates that could not be separated on beta-CD bonded phase liquid chromatography (LC) columns with this technique. Likewise there were some compounds that could be resolved with the LC approach that failed to separate with the present TLC method. In cases of racemates that could be resolved by either approach, it was found that the retention order was exactly opposite for the two methods. Enantiomeric resolution is highly dependent on mobile phase composition. In particular, the type and amount of organic modifier as well as the concentration of beta-CD affect the observed resolution. Possible reasons for the chromatographic behavior are discussed. Several diastereoisomeric compounds were separated as well, including steroid epimers and pharmaceutical compounds.

Amino Acids↗

PubMed2000

Novel ferrocenic artemisinin derivatives: synthesis, in vitro antimalarial activity and affinity of binding with ferroprotoporphyrin IX.

Following our search for novel compounds with high antimalarial activity, a series of artemisinin (QHS) derivatives containing a ferrocenic nucleus was prepared and tested in vitro against Plasmodium falciparum strains. Two new metallocenic derivatives (1 and 3) were found as potent as QHS. All compounds showed a capacity to bind with ferroprotoporphyrin IX. A decrease in the Soret band absorbance of ferroprotoporphyrin IX, resulting from the addition of different drugs concentrations, was shown. The association stoichiometry of compounds to ferroprotoporphyrin IX appears to be 1:2 at equilibrium, with an intermediate 1:1 complexation. These results appear to strengthen the role of adducts between artemisinin derivatives and heme in generation of artemisinin radicals. Such interaction of artemisinin ferrocenyl derivatives with ferroprotoporphyrin IX and its biological significance could form a basis in future drug development.

Animals↗

PubMed2002

Carbon nanotubes from organometallic precursors.

Multiwalled as well as single-walled carbon nanotubes are conveniently prepared by the pyrolysis of organometallic precursors such as metallocenes and phthalocyanines in a reducing atmosphere. More importantly, pyrolysis of organometallics alone or in mixture with hydrocarbons yields aligned nanotube bundles with useful field emission and hydrogen storage properties. By pyrolysis of organometallics in the presence of thiophene, Y-junction nanotubes are obtained in large quantities. The Y-junction tubes have a good potential in nanoelectronics. Carbon nanotubes prepared from organometallics are useful to prepare nanowires and nanotubes of other materials such as BN, GaN, SiC, and Si(3)N(4).

Biosensing Techniques↗

PubMed2004

Organolanthanide-catalyzed hydroamination.

Organolanthanides are highly efficient catalysts for inter- and intramolecular hydroamination of various C-C unsaturations such as alkenes, alkynes, allenes, and dienes. Attractive features of organolanthanide catalysts include very high turnover frequencies and excellent stereoselectivities, rendering this methodology applicable to concise synthesis of naturally occurring alkaloids and other polycyclic azacycles. The general hydroamination mechanism involves turnover-limiting C-C multiple bond insertion into the Ln-N bond, followed by rapid protonolysis by other amine substrates. Sterically less encumbered ligand designs have been developed to improve reaction rates, and metallocene and nonmetallocene chiral lanthanide complexes have been synthesized for enantioselective hydroamination.

Journal Article↗

PubMed2000

What do titano- and zirconocenes do with diynes and polyynes?

A thorough investigation of the reactions of diynes, R(C&tbd1;C)(2)R, and polyynes, R(C&tbd1;C)(n)()R, with titanocene and zirconocene was performed using the metallocene sources Cp(2)M(L)(eta(2)-Me(3)SiC&tbd1;CSiMe(3)) (M = Ti, L = -; M = Zr, L = THF, pyridine). The conversions show an array of different products generated in complexation, coupling, and cleavage reactions. These results include remarkable structures (e.g., five-membered metallacyclocumulenes) and reactions (e.g., C-C single-bond cleavage). In addition, the first C-C single-bond metathesis in homogeneous solution was discovered. The presented findings have been supported by theoretical studies.

Alkenes↗

PubMed2001

New molecular assemblies of redox isomers, [CrIII(X4SQ)3-n(X4Cat)n]-n (X = Cl and Br; n = 0, 1, and 2), with metallocenium cations, [MIIICp2]+ (M = Co and Fe): X-ray crystal structures and physical properties.

A series of redox isomers of [CrIII(X4SQ)(X4Cat)2]2-, [CrIII(X4SQ)2(X4Cat)]-, and [CrIII(X4SQ)3]0 (X = Cl and Br, SQ = semiquinonate, and Cat = catecholate) have been synthesized and characterized as charge-transfer (CT) compounds with metallocenium cations: (CoIIICp2)2[CrIII(Cl4SQ)(Cl4Cat)2] (1), (CoIIICp2)2[CrIII(Br4SQ)(Br4Cat)2] (2), (FeIIICp2)[CrIII(Cl4SQ)2(Cl4Cat)].C6H6 (4), (FeIIICp2)[CrIII(Br4SQ)2(Br4Cat)].CS2 (5), and (FeIIICp2)[CrIII(Cl4SQ)2(Cl4Cat)][CrIII(Cl4SQ)3] (6). First, the oxidation states of the chromium complexes are strongly dependent on the redox potentials of the metallocenes used. The CoIICp2, exhibiting stronger reduction power than FeIICp2, is useful for two-electron reduction of the [CrIII(X4SQ)3]0, affording [CrIII(X4SQ)(X4Cat)2]2- (1 and 2), which are first isolated and crystallographically characterized in the solid state. In contrast the reaction with FeIICp2 affords only [CrIII(X4SQ)2(X4Cat)]- (4 and 5). Second, solvents influence crystal structures of these compounds. The solvent set of C6H6/CS2 gives 1:1:C6H6 compound 4 with unique charged anions, [CrIII(Cl4SQ)2(Cl4Cat)]-, while the other set, n-C6H12/CS2, affords 1:2 compound 6 including the two redox isomers, [CrIII(Cl4SQ)2(Cl4Cat)]- and [CrIII(Cl4SQ)3]0. The [CrIII(X4SQ)(X4Cat)2]2- anions in 1 and 2 show no significant interconnection between them (discrete type), while the [CrIII(X4SQ)2(X4Cat)]- anions in 4-6 show one-dimensional column-type structures with the aid of intermolecular stacking interactions of the ligand moieties. The anions in 4 show additional stacking interaction with the [FeIIICp2]+ to form one-dimensional ...[D][A][S][D][A]... (D = [FeIIICp2]+, A = [CrIII(Cl4SQ)2(Cl4Cat)]-, and S = C6H6) type mixed-stack arrangements similar to that of previously reported (CoIIICp2)[CrIII(Cl4SQ)2(Cl4Cat)].C6H6 (3). Compound 6 forms a two-dimensional sheet structure where the two redox isomers, [CrIII(Cl4SQ)2(Cl4Cat)]- and [CrIII(Cl4SQ)3]0, are included. The sheet is regarded as a mixed-valence molecular assembly. Two types of the anions, [CrIII(X4SQ)(X4Cat)2]2- (1 and 2) and [CrIII(X4SQ)2(X4Cat)]- (4-6), exhibiting an intramolecular mixed-valence state, show intramolecular intervalence CT transition (IVCT) from the Cat to the SQ at near 5800 and 4300 cm-1, respectively, both in the solution and in the solid states. The intermolecular mixed-valence state of 6 was characterized by absorption spectroscopy, electric conductivity, and SQUID magnetometry. Interestingly, this mixed-valence state of the chromium module is dependent on the redox active nature of the coordinated ligands.

Journal Article↗

PubMed2001

Group 4 dimethylmetallocenes: improved synthesis and reactivity studies.

Group 4 dimethylmetallocenes are catalyst precursors for the methylmetallocenium/borate catalyst systems for olefin polymerization, and they are usually prepared by methylation (with MeMgCl or MeLi) of the parent metallocene dichlorides. We describe here a simpler preparation of a series of bisindenyldimethylmetallocenes carried out by reacting the pi-ligand with a 2-fold excess of MeLi, and then MtCl(4) (Mt = Ti, Zr, Hf). This simple, one-pot method produces the dimethylated complexes in higher overall yield, and saves on reaction time and solvents. Ind(2)MtMe(2) (1, Mt = Ti; 2a, Mt = Zr; 3, Mt = Hf), (4,7-Me(2)Ind)(2)ZrMe(2) (4), rac/meso-[C(2)H(4)(Ind)(2)]ZrMe(2) (5), meso-[C(2)H(4)(4,7-Me(2)Ind)(2)]ZrMe(2) (m-6a), and meso-[C(2)H(4)(4,7-Me(2)Ind)(2)]HfMe(2) (m-7a) have been prepared in 40-80% isolated yields. 2a reacts with 1-4 equiv of t-BuOH to give the mono-tert-butoxy derivative 2b, Ind(2)ZrMe(O-t-Bu), while reaction with 2 equiv of C(6)F(5)OH cleanly affords Ind(2)Zr(OC(6)F(5))(2) (2c). Analogously, in the presence of 2 equiv of t-BuOH, m-6a gives meso-[C(2)H(4)(4,7-Me(2)Ind)(2)]ZrMe(O-t-Bu) (m-6b) with replacement of the outward methyl group only, as established by NMR analysis; meso-[C(2)H(4)(4,7-Me(2)Ind)(2)]Zr(OC(6)F(5))(2) (m-6c) is obtained by reaction with 2 equiv of C(6)F(5)OH. The molecular structures of m-6a and m-6c are also described.

Journal Article↗

PubMed2004

Structure, energetics, and bonding of first row transition metal pentazolato complexes: a DFT study.

Quantum chemical calculations with gradient-corrected (B3LYP) density functional theory for the mono- and bispentazolato complexes of the first row transition metals (V, Cr, Mn, Fe, Co, and Ni), the all-nitrogen counterparts of metallocenes, were performed, and their stability was investigated. All possible bonding modes (e.g. eta1, eta2, eta3, and eta5) of the pentazolato ligand to the transition metals have been examined. The transition metal pentazolato complexes are predicted to be strongly bound molecules. The computed total bond dissociation enthalpies that yield free transition metal atoms in their ground states and the free pentazolato ligands were found in the range of 122.0-201.9 (3.7-102.3) kcal mol(-1) for the bispentazolato (monopentazolato) complexes, while those yielding M2+ and anionic pentazolato ligands were found in the range of 473.2-516.7 (273.6-353.5) kcal mol(-1). The electronic ground states of azametallocenes along with their spectroscopic properties (IR, NMR, and UV-vis) obtained in a consistent manner across the first transition metal series provide means for discussion of their electronic and bonding properties, the identification of the respective azametallocenes, and future laboratory studies. Finally, exploring synthetic routes to azametallocenes it was found that a [2 + 3] cycloaddition of dinitrogen to a coordinated azide ligand with nickel(II) does not seem to provide a promising synthetic route for transition metal pentazolato complexes while the oxidative addition of phenylpentazole and fluoropentazole to Ni(0) bisphosphane complexes merits attention for the experimentalists.

Journal Article↗

PubMed2004

Structure and dynamics of a dihydrogen/hydride ansa molybdenocene complex.

In contrast to [Cp(2)MoH(3)](+), which is a thermally stable trihydride complex, the ansa-bridged analogue [(eta-C(5)H(4))(2)CMe(2)MoH(H(2))](+) (1) is a thermally labile dihydrogen/hydride complex. Partial deuteration of the hydride ligands allows observation of J(H)(-)(D) = 11.9 Hz in 1-d(1) and 9.9 Hz in 1-d(2) (245 K), indicative of a dihydrogen/hydride structure. There is a slight preference for deuterium to concentrate in the dihydrogen ligand. A rapid dynamic process interchanges the hydride and dihydrogen moieties in complex 1. Low temperature (1)H NMR spectra of 1 give a single hydride resonance, which broadens at very low temperature due to rapid dipole-dipole relaxation (T(1) = 23 ms (750 MHz, 175 K) for the hydride resonance in 1). Low temperature (1)H NMR spectra of 1-d(2) allow the observation of decoalescence at 180 K into two resonances. The bound dihydrogen ligand exhibits hindered rotation with DeltaG(150) = 7.4 kcal/mol, but H atom exchange is still rapid at all accessible temperatures (down to 130 K). Density functional calculations confirm the dihydrogen/hydride structure as the ground state for the molecule and give estimates for the energy of two hydrogen exchange processes in good agreement with experiment. The presence of the C ansa bridge is shown to decrease the ability of the metallocene fragment to donate to the hydrogens, thus stabilizing the (eta(2)-H(2)) unit and modulating the barrier to H(2) rotation.

Journal Article↗

PubMed2005

Synthesis, structure, and ligand-based reduction reactivity of trivalent organosamarium benzene chalcogenolate complexes (C(5)Me(5))(2)Sm(EPh)(THF) and [(C(5)Me(5))(2)Sm(mu-EPh)](2).

To compare the ligand-based reduction chemistry of (EPh)(-) ligands in a metallocene environment to the sterically induced reduction chemistry of the (C(5)Me(5))(-) ligands in (C(5)Me(5))(3)Sm, (C(5)Me(5))(2)Sm(EPh) (E = S, Se, Te) complexes were synthesized and treated with substrates reduced by (C(5)Me(5))(3)Sm: cyclooctatetraene; azobenzene; phenazine. Reactions of PhEEPh with (C(5)Me(5))(2)Sm(THF)(2) and (C(5)Me(5))(2)Sm produced THF-solvated monometallic complexes, (C(5)Me(5))(2)Sm(EPh)(THF), and their unsolvated dimeric analogues, [(C(5)Me(5))(2)Sm(mu-EPh)](2), respectively. Both sets of the paramagnetic benzene chalcogenolate complexes were definitively identified by X-crystallography and form homologous series. Only the (TePh)(-) complexes show reduction reactivity and only upon heating to 65 degrees C.

Journal Article↗

PubMed2006

Investigation of vanadocene(IV) alpha-amino acid complexes: synthesis, structure, and behavior in physiological solutions, human plasma, and blood.

This work is focused on investigating the interaction of antitumor active metallocene vanadocene dichloride (Cp2VCl2) and amino acids in aqueous solution at physiological pH. Sixteen vanadocene amino acid complexes [Cp2V(aa)][X] (aa = gly, ala, val, leu, ile, phe, his, and trp; X = Cl, PF6) were prepared and characterized on the basis of spectral measurements (EPR, MS, IR, Raman). Amino acids are coordinated to the vanadocene fragment through the oxygen atom of the carboxylic group and the nitrogen of the amino group, resulting in a five-membered chelate ring. Complexes [Cp2V(val)][PF6] and [Cp2V(ile)][PF6] have been characterized by X-ray structure analyses. It was evidenced that all prepared complexes are stable in both aqueous solutions with physiological pH and in therapeutic NaCl solutions. EPR spectra of vanadocene amino acid complexes in Krebs-Ringer solution in human blood plasma and in whole blood showed that these complexes react with the hydrogen carbonate anion present forming complex Cp2V(O2CO).

Amino Acids↗

PubMed2005

Heavy-metal aromatic and conjugated species: rings, oligomers, and chains of tin in Li(9)(-)(x)EuSn(6+)(x), Li(9)(-)(x)CaSn(6+)(x), Li(5)Ca(7)Sn(11), Li(6)Eu(5)Sn(9), LiMgEu(2)Sn(3), and LiMgSr(2)Sn(3).

The title compounds were synthesized from the elements by heating the corresponding mixtures at high temperature. Their structures were determined from single-crystal X-ray diffraction. Li(9)(-)(x)()EuSn(6+)(x)(), Li(9)(-)(x)()CaSn(6+)(x)(), Li(5)Ca(7)Sn(11), and Li(6)Eu(5)Sn(9) contain columns of stacked aromatic pentagons of Sn(5)(6)(-) that are analogous to the cyclopentadienyl anion C(5)H(5)(-). The pentagons are separated with Ca(2+) or Eu(2+) in the columns and resemble a polymeric metallocene. In addition to the columns, the isostructural Li(9)(-)(x)()EuSn(6+)(x)() and Li(9)(-)(x)()CaSn(6+)(x)() contain isolated tin atoms and bent tin trimers while Li(5)Ca(7)Sn(11) and Li(6)Eu(5)Sn(9) contain flat zigzag hexamers and flat zigzag infinite chains of tin, respectively. The isostructural LiMgEu(2)Sn(3) and LiMgSr(2)Sn(3) do not contain columns of pentagons but only flat zigzag infinite chains of tin. The aromaticity of the pentagons and the conjugation of the pi-systems of the hexamers and the infinite chains are discussed. The title compounds are also characterized by magnetic and conductivity measurements.

Calcium↗

PubMed2005

P-S Bond scission by bis(cyclopentadienyl)molybdenum(IV) dichloride, Cp(2)MoCl(2)(aq): first documented example of an organometallic complex hydrolyzing thiophosphinates.

Thiophosphinate hydrolysis involving P-S bond scission is desirable for the degradation of organophosphate neurotoxins, and we report the first case for such a hydrolytic process by an organometallic compound. The metallocene, bis(cyclopentadienyl)molybdenum(IV) dichloride, Cp(2)MoCl(2) (Cp = eta(5)-C(5)H(5)), hydrolyzes a variety of thioaryl diphenylphosphinates in an aqueous THF solution. P-S scission of p-methoxythiophenyl diphenylphosphinate has a 500-fold rate of acceleration in the presence of Cp(2)MoCl(2)(aq) with activation parameters of 20(3) kcal mol(-)(1) and -15(3) cal mol(-)(1) K(-)(1) for DeltaH(double dagger) and DeltaS(double dagger), respectively. These activation parameters and the rate acceleration are consistent with an intermolecular hydrolytic process in which the Cp(2)Mo serves as a Lewis acid to activate the phosphinate for nucleophilic attack. Furthermore, rho = 2.3 (25 degrees C) which indicates a single nonconcerted mechanism in which the rate determining step is the nucleophilic attack on the activated phosphinate.

Crystallography, X-Ray↗

PubMed2006

Lanthanum and alkali metal coordination chemistry of the bis(dimethylphenylsilyl)amide ligand.

The coordination chemistry of the bis(dimethylphenylsilyl)amide ligand, [N(SiMe2Ph)2]1-, with sodium, potassium, and lanthanum has been investigated for comparison with the more commonly used [N(SiMe3)2]1- and [N(SiHMe2)2]1- ligands. HN(SiMe2Ph)2 reacts with KH to produce KN(SiMe2Ph)2, 1, which crystallizes from toluene as the dimer [KN(SiMe2Ph)2(C7H8)]2, 2. The structure of 2 shows that the [N(SiMe2Ph)2]1- ligand can function as a polyhapto ligand with coordination from each phenyl group as well as the normal nitrogen ligation and agostic methyl interactions common in methylsilylamides. Each potassium in 2 is ligated by an eta4-toluene, two bridging nitrogen atoms, and an eta2-phenyl, an eta1-phenyl, and an eta1-methyl group. KN(SiMe2Ph)2 crystallizes from toluene in the presence of 18-crown-6 to make the monometallic complex (18-crown-6)KN(SiMe2Ph)2, 3, in which [N(SiMe2Ph)2]1- functions as a simple monodentate ligand through nitrogen. The reaction of HN(SiMe2Ph)2 with NaH in THF at reflux for 2 days generates Na[N(SiMe2Ph)2], 4, which crystallizes as the solvated dimer {(THF)Na[mu-eta1:eta1-N(SiMe2Ph)2]}2, 5. A lanthanide metallocene derivative of [N(SiMe2Ph)2]1- was obtained by reaction of K[N(SiMe2Ph)2] with [(C5Me5)2La][(mu-Ph)2BPh2]. Crystals of (C5Me5)2La[N(SiMe2Ph)2], 6, show agostic interactions between lanthanum and methyl groups of each silyl substituent. The [N(SiMe3)2]1- analogue of 3, (18-crown-6)KN(SiMe3)2, 7, was also structurally characterized for comparison.

Journal Article↗

PubMed1996

First Mixed Fluoro-Chloro Group 4 Organometallics: Synthesis and Spectroscopic and Structural Characterization of [{(C(5)Me(5))ZrF(2)Cl}(4)], [{(C(5)Me(5))HfF(2)Cl}(4)], [(C(5)Me(5))(4)Zr(4)(&mgr;-F)(2)(&mgr;-F(2))(2)(&mgr;-Cl)(2)Cl(4)], [(C(5)Me(5))(4)Hf(4)(&mgr;-F)(2)(&mgr;-F(2))(2)(&mgr;-Cl)(2)Cl(4)], [(C(5)Me(4)Et)(2)ZrClF], and [(C(5)Me(5))(2)HfClF].

Tetrameric [{(C(5)Me(5))MF(3)}(4)] (M = Zr, Hf) react smoothly with Me(3)SiCl in CH(2)Cl(2) at room temperature to give [{(C(5)Me(5))ZrF(2)Cl}(4)] (1) and [{(C(5)Me(5))HfF(2)Cl}(4)] (2), respectively, in high yield. Treatment of [{(C(5)Me(5))MF(3)}(4)] (M = Zr, Hf) with Me(2)AlCl in toluene gives mixtures of 1 and [(C(5)Me(5))(4)Zr(4)(&mgr;-F)(2)(&mgr;-F(2))(2)(&mgr;-Cl)(2)Cl(4)] (3), and 2 and [(C(5)Me(5))(4)Hf(4)(&mgr;-F)(2)(&mgr;-F(2))(2)(&mgr;-Cl)(2)Cl(4)] (4), respectively, in an approximately 1:1 molar ratio. Metallocene type complexes [(C(5)Me(4)Et)(2)ZrCl(2)] and [(C(5)Me(5))(2)HfCl(2)] react with 1 equiv of Me(3)SnF to give [(C(5)Me(4)Et)(2)ZrClF] (5) and [(C(5)Me(5))(2)HfClF] (6), respectively. The complexes 1-6 were characterized by spectroscopic methods ((1)H and (19)F NMR and mass spectroscopy). The solid state structures of 1, 3, and 5 were determined by single-crystal X-ray diffraction analyses.

Journal Article↗

PubMed1996

Synthesis and Reaction Chemistry of the Disodium Alkoxide of 2,6-Bis(trifluoromethyl)-2,6-dihydroxy-3,3,4,4,5,5-hexafluorooxane.

The disodium alkoxide of 2,6-bis(trifluoromethyl)-2,6-dihydroxy-3,3,4,4,5,5-hexafluorooxane, C(7)F(12)O(3)Na(2), 1, was prepared by reaction of the corresponding diol with MeONa in MeOH. This cyclic alkoxide readily mimics the reaction chemistry of the lithium and sodium alkoxides of perfluoropinacol. The reaction of the alkoxide 1 with covalent dichlorides and metallocene dichlorides yields a series of novel bicyclic ring systems. The crystal structure of the trioxasilane, 3, formed from (CH(3))(2)SiCl(2) was determined to provide structural information about these ring systems. Crystal data: C(9)H(6)O(3)F(12)Si, fw = 418.21 u, orthorhombic space group, Pnma (No. 62), a = 15.822(3) Å, b = 12.163(3) Å, c = 7.373(2) Å, V = 1418.9(4) Å(3), and D(calc) = 1.96 g cm(-)(3) for Z = 4 (molecule possesses mirror symmetry). Least-squares refinement on 1075 observed reflections (I > 3sigma(I)) converged with R = 0.0357 and R(w) = 0.0478.

Journal Article↗

PubMed1998

Coordination Chemistry of N-Alkylbenzamide-2,3-dithiolates as an Approach to Poly(dithiolate) Ligands: 1,4-Bis[(2,3-dimercaptobenzamido)methyl]benzene and Its Chelate Complex with the (C(5)H(5))Ti Fragment.

The bidentate dithiolate ligands N,N-diethyl-2,3-dimercaptobenzamide (H(2)-1), bis(N,N-diethyl-2,3-dimercaptoterephthalamide (H(2)-2), and 1,4-bis(hydroxymethyl)-2,3-dimercaptobenzene (H(4)-3) were synthesized from 2,3-dimercaptobenzoic acid or 2,3-dimercaptoterephthalic acid. The air-sensitive ligands form metallocene complexes of the type [(eta(5)-C(5)H(5))(2)Ti(1)] (13), [(eta(5)-C(5)H(5))(2)Mo(1)] (15), [(eta(5)-C(5)H(5))(2)Ti(3)] (16), and [(eta(5)-C(5)H(5))(2)Ti(2)] (17). Complexes 15 and 16 were characterized by X-ray diffraction. Selected crystallographic details for 15 are as follows: formula C(21)H(23)MoNOS(2); M = 465.49; Pbca; a = 12.536(3), b = 14.313(3), c = 22.463(3) Å; V = 4031(2) Å(3); Z = 8; R = 3.56 and R(w) = 4.49 for 2111 structure factors (F(o)(2) >/= 3sigma(F(o)(2))) and 254 refined parameters. The molybdenum complex 15 shows an almost planar Mo(&mgr;-S)(2)C(2) chelate ring. Selected crystallographic details for 16 are as follows: formula C(18)H(18)O(2)S(2)Ti; M = 378.35; P&onemacr;; a = 10.1778(11), b = 11.5806(14), c = 22.967(3) Å; alpha = 96.42(1), beta = 101.74(1), gamma = 108.82(1) degrees; V = 2462.3(5) Å(3); Z = 6; R = 4.79 and R(w) = 13.27 for 5426 structure factors (I >/= 2sigma(I)) and 766 refined parameters. All titanocene derivatives assume the envelope conformation. The free activation energy for the flip around the S-S axis was determined for 13 to be 69 kJ/mol. The bis(dithiolate) ligand 1,4-bis[(2,3-dimercaptobenzamido)methyl]benzene (H(4)-4) was prepared from 2,3-dimercaptobenzoic acid and converted into the dinuclear air-stable titanocene complex [{(eta(5)-C(5)H(5))(2)Ti}(2)(4)] (19). Complex 19 reacts with HCl/CHCl(3) with liberation of free H(4)-4 while reaction with NMe(4)Cl results in an intramolecular dithiolate shift under formal liberation of [(C(5)H(5))(3)TiCl] and formation of the square-pyramidal chelate complex (NMe(4))[(eta(5)-C(5)H(5))Ti(4)], (NMe(4))[20]. Crystallographic details for (NMe(4))[20].CH(2)Cl(2) are as follows: formula C(32)H(35)Cl(2)N(3)O(2)S(4)Ti; M = 740.67; P&onemacr;; a = 11.579(4), b = 12.210(4), c = 14.016(4) Å; alpha = 112.28(2), beta = 94.46(3), gamma = 104.22(3) degrees; V = 1744.9(10) Å(3); Z = 2; R = 5.35 and R(w) = 12.84 for 2870 structure factors (I >/= 2sigma(I)) and 397 refined parameters. The chelate rings in [20](-) assume an endo/exo conformation.

Journal Article↗