5,5'-Bis-(trinitromethyl)-3,3'-bi-(1,2,4-oxadiazole): a stable ternary CNO-compound with high density.

5,5'-Bis-(trinitromethyl)-3,3'-bi-(1,2,4-oxadiazole) is a new ternary CNO-compound. It has been synthesized by nitration of diammonium 5,5'-bis-(dinitromethanide)-3,3'-bi-(1,2,4-oxadiazole) with nitronium tetrafluoroborate. Single crystal X-ray diffraction studies show a remarkable high density. Thermal stability and sensitivities of the new compound were determined by differential scanning calorimetry (DSC) and standardized drop hammer and friction tests.

Morphological and chemical influences on alumina-supported palladium catalysts active for the gas phase hydrogenation of crotonaldehyde.

A series of five alumina-supported palladium catalysts have previously been prepared and characterised by a combination of CO chemisorption and infrared spectroscopy. The reactive attributes of these catalysts are examined using the hydrogenation of crotonaldehyde as a test reaction, using a modified infrared gas cell as a batch reactor. Periodic scanning of the infrared spectrum of the gaseous phase present over the Pd/Al(2)O(3) catalysts was used to construct reaction profiles. Four of the catalysts were able to facilitate a 2-stage hydrogenation process (crotonaldehyde → butanal → butanol), whilst one catalyst was totally selective for the first stage hydrogenation process (crotonaldehyde → butanal). Rate coefficients for the first and second stage hydrogenation processes are normalised to the number of surface palladium atoms for the particular catalyst. Correlation of these kinetic parameters as a function of mean particle size indicates the first stage process to be structure insensitive, whilst the second stage hydrogenation is structure sensitive. Chlorine residues associated with the preparative process of one of the catalysts is seen to selectively poison the second stage hydrogenation process for that catalyst. Structure/activity relationships are considered to explain the observed trends.

Phase stability of lithium azide at pressures up to 60 GPa.

We studied lithium azide (LiN(3)) by x-ray diffraction and Raman spectroscopy at hydrostatic compression up to pressures above 60 GPa at room temperature. The results of x-ray diffraction analyses reveal the stability of the ambient-pressure C 2/m crystal structure up to the highest pressure. The pressure dependence of librational modes provides evidence for an order-disorder transition at low pressures (below 3 GPa), similar to the transition observed previously at low temperatures. The observed structure stability indicates that this transition is not associated with structural changes. The phase stability of LiN(3) is in contrast to that of sodium azide (which is isostructural at ambient pressure), for which a set of phase transitions has been reported at pressures below 50 GPa.

Regioselective synthesis of bis(2-halo-3-pyridyl) dichalcogenides (E = S, Se and Te): directed ortho-lithiation of 2-halopyridines.

A novel method for the preparation of hitherto unknown symmetrical bis(2-halo-3-pyridyl) dichalcogenides (E = S, Se and Te) by the oxidation of intermediate 2-halo-3-pyridyl chalcogenolate, prepared by lithiation of 2-halo pyridines using lithium diisopropylamine is being reported. All the newly synthesized compounds have been characterized through elemental analysis employing various spectroscopic techniques, namely, NMR ((1)H, (13)C, (77)Se), infrared, mass spectrometry, and X-ray crystal structures in representative cases.

A theoretical and experimental study on the Lewis acid-base adducts (P(4)E(3)).(BX(3)) (E = S, Se; X = Br, I) and (P(4)Se(3)).(NbCl(5)).

The Lewis acid-base adducts (P(4)E(3)).(BX(3)) (E = S, Se; X = Br, I) and (P(4)Se(3)).(NbCl(5)) have been prepared and characterized by Raman, IR, and solid-state (31)P MAS NMR spectroscopy. Hybrid density functional calculations (B3LYP) have been carried out for both the apical and the basal (P(4)E(3)).(BX(3)) (E = S, Se; X = Br, I) adducts. The thermodynamics of all considered species has been discussed. In accordance with solid-state (31)P MAS NMR and vibrational data, the X-ray powder diffraction structures of (P(4)S(3)).(BBr(3)) [monoclinic, space group P2(1)/m (No. 11), a = 8.8854(1) A, b = 10.6164(2) A, c = 6.3682(1) A, beta = 108.912(1) degrees, V = 568.29(2) A(3), Z = 2] and (P(4)S(3)).(BI(3)) [orthorhombic, space group Pnma (No. 62), a = 12.5039(5) A, b = 11.3388(5) A, c = 8.9298(4) A, V = 1266.09(9) A(3), Z = 4] indicate the formation of an apical P(4)S(3) complex in the reaction of P(4)S(3) with BX(3) (X = Br, I). Basal adducts are formed when P(4)Se(3) is used as the donor species. Vibrational assignment for the normal modes of these adducts has been made on the basis of comparison between theoretically obtained and experimentally observed vibrational data.

Spectroscopic and structural studies on polyfluorophenyl tellurides and tellurium(IV) dihalides.

Bis(fluorophenyl) tellurides R2Te (R = C6F2H3 (1), CF3C6F4 (2), CF3C6F4OC6F4 (3), and C6F5 (4)) are synthesized by the facile reaction of Na2Te with bromo-fluorobenzenes, RBr. The corresponding bis(fluorophenyl)tellurium(IV) dihalides, R2TeHal2 (Hal = F, Cl, and Br) (5-16), are obtained by the oxidation of 1-4 with mild halogenating agents (XeF2, SO2Cl2, and Br2). The dihalides show temperature-dependent NMR spectra. On the basis of the 19F NMR spectra of the two series, (C6F2H3)2TeHal2 (Hal = F (5), Cl (9), and Br (13)) and R2TeCl2 (R = C6F2H3 (9), CF3C6F4 (10), CF3C6F4OC6F4 (11), and C6F5 (12)), the coalescence temperatures, T(c), and free enthalpies, DeltaG, of rotation of the TeC bonds are determined. The activation enthalpies for the dichlorides/dibromide 9-13 are in the range of 14.4-15.2 kcal mol(-1) and that for the difluoride 5 is considerably lower at 10.7 kcal mol(-1). In addition to thorough spectroscopic characterization of 1-16, the crystal structures of the monotellurides 2 and 4 as well as of the tellurium(IV) dihalides 5, 6, 9, 10, and 13 were determined. The dihalides show interesting intermolecular Te...Hal contacts, significantly shorter than the sum of the van der Waals radii, leading to different networks of association.

[N(2)H(5)](+)(2)[N(4)C-N=N-CN(4)](2-): a new high-nitrogen high-energetic material.

The reaction of [N(2)H(5)](+)(2)[SO(4)](2-) with barium 5,5'-azotetrazolate gave new high-energy-density materials (HEDM) based on the 5,5'-azotetrazolate dianion. The dihydrazinium salt of [N(4)C-N=N-CN(4)](2-) 1, its dihydrate 2, and its dihydrazinate 3 were prepared in high yield. Synthesis in water afforded yellow needles of [N(2)H(5)](2)(+)[N(4)C-N=N-CN(4)](2-).2H(2)O (2): monoclinic, P2/c, a = 8.958(2) A, b = 3.6596(7) A, c = 16.200(3) A, beta = 96.834(3) degrees, V = 527.3(2) A(3), Z = 2; synthesis in anhydrous hydrazine gave yellow [N(2)H(5)](2)(+)[N(4)C-N=N-CN(4)](2-).2N(2)H(4) (3): triclinic, P1, a = 4.6208(6) A, b = 8.585(1) A, c = 9.271(1) A, alpha = 108.486(2) degrees, beta = 95.290(2) degrees, gamma = 102.991(2) degrees, V = 334.51(8) A(3), Z = 1. The compounds were characterized by elemental analysis and vibrational (IR, Raman) and multinuclear NMR spectroscopy ((1)H, (13)C, (14)N, (15)N). The new compounds represent new high-nitrogen HEDMs with one of the highest nitrogen contents reported to date ([N(2)H(5)](+)(2)[N(4)C-N=N-CN(4)](2-) 85.2%; [N(2)H(5)](+)(2)[N(4)C-N=N-CN(4)](2-).2H(2)O 73.3%; [N(2)H(5)](+)(2)[N(4)C-N=N-CN(4)](2-).2N(2)H(4) 85.7%). The standard heat of formation of the solvate-free compound 1 was computed at the MP2(FULL)/6-311+G(d,p) level of theory to be DeltaH degrees (f) = 264 kcal mol(-1), which translates to 1147 kcal kg(-1) and is one of the highest ever reported. The compounds are stable at room temperature, almost insensitive to friction and impact, but detonate violently when the explosion is initiated, e.g., by rapid heating over the decomposition temperature or by using an initiator.

Highly energetic tetraazidoborate anion and boron triazide adducts.

The first crystal structures of the highly energetic tetraazidoborate anion and boron triazide adducts with quinoline and pyrazine as well as of tetramethylpiperidinium azide have been determined. Synthesis procedures and thorough characterization by spectroscopic methods of these hazardous materials are given. Quantum chemical calculations were carried out for B(N(3))(4)(-), B(N(3))(3), C(5)H(5)N.B(N(3))(3), (N(3))(3)B.NC(4)H(4)N.B(N(3))(3), and the hypothetical C(3)H(3)N(3).[B(N(3))(3)](3) at HF, MP2, and B3-LYP levels of theory. The structure of tetraazidoborate was optimized to S(4) symmetry and confirmed the results obtained from the X-ray diffraction analysis. The dissociation enthalpies for the pyridine (model for quinoline) as well as for the pyrazine adduct were calculated. For pyridine-boron triazide a value of 10.0 kcal mol(-1) (for pyrazine-bis(boron triazide) an average of 2.35 kcal mol(-1) per BN unit) was obtained.

Antitumor activity of ionic niobocene and molybdenocene complexes in high oxidation states.

Four air-stable niobocene complexes [(C5H5)2NbCl2]+X- with X = BF4, AsF6, SbF6, SO3CF3 and the molybdenocene derivative [(C5H5)2MoCl2]2+[SbF6]2- were investigated for antitumor properties against Ehrlich ascites tumor in female CF1 mice. All compounds are new, salt-like complexes containing a cationic metallocene moiety, where the early transition metals niobium and molybdenum in the high oxidation states +5 and +6 function as central atoms. The niobocene complexes containing tetrafluoroborate (BF4-) or trifluoromethanesulfonate (CF3SO3-) as anions only induced a maximal cure rate of 50% and led to increases in life span of 182% and 178% following application of optimal doses. The other two niobocene compounds with hexafluoroarsenate (AsF6-) and hexafluoroantimonate (SbF6-) as anions and the molybdenocene derivative [(C5H5)2MoCl2]2+[SbF6]2- effected a maximal cure rate of 100% and increases in life span of 346%, 376%, and 332%, respectively, determined on the key date, i.e., on day 90 after transplantation. On applying the niobocene hexafluoroantimonate complex [(C5H5)2NbCl2] +[SbF6]-, the optimal dose range with a cure rate of 100% was rather broad and extended from 20 mg/kg to 40 mg/kg. Correspondingly, the value of the therapeutic index (TI) was high and amounted to 7.2. In the case of the niobocene hexafluoroarsenate and the molybdenocene hexafluoroantimonate complexes, the TI value decreased to 5.3 and 2.6 respectively. Neither impairments of the general condition nor any conspicuous symptoms could be detected after application of therapeutic doses of the five compounds investigated. Compared to the neutral niobocene dichloro complex [(C5H5)2NbCl2], the therapeutic range of the ionic niobocene derivative [(C5H5)2NbCl2]+[SbF6]- was broadened, the TI value markedly elevated from 2.9 to 7.2, and the toxic symptoms were impressively reduced. The niobocene hexafluoroantimonate complex was the most effective compound investigated in the present study.

Ionic rhenocene derivatives with antitumor activity.

The antitumor activity of the three air-stable bis(cyclopentadienyl)rhenium derivatives [(C5H5)2-ReCl2]+Cl-,[(C5H5)2ReCl2]+[AsF6]- , and [(C5H5)2-ReCl2]+[SbF6]- was tested against Ehrlich ascites tumor in female CF1 mice. All three compounds contain the group-7 transition metal rhenium in the +5 oxidation state as their central metal atom. They are ionic, salt-like complexes that are composed of the cationic [(C5H5)2ReCl2]+ moiety and one of the negatively charged counterions Cl-, AsF6-, or SbF6-. Both the chloro and the hexafluoroarsenate complexes induced a maximal cure rate of 100% when given either in a dose range of 120-160 mg/kg (rhenocene trichloride) or at a single dose of 180 mg/kg (hexafluoroarsenate derivative). The hexafluoroantimonate complex effected a maximal cure rate of only 50% at 60 mg/kg. For the two former compounds, the values for the therapeutic index (TI) amounted to 1.7 and 2.1, respectively. No impairment of the general condition or pathologic symptoms in the viscera could be detected by observation of the animals during the days following treatment with therapeutic doses or by autopsy of the surviving animals on the key date (day 90). The rhenocene derivatives investigated in the present study represent a new class of antitumor metallocene compounds as well as the first rhenium(V) complexes exerting cytostatic activity.

Antitumor activity of an ionic titanocene tetrachloroferrate derivative against some solid experimental tumors.

The metallocene complex bis(cyclopentadienyl)acetonitrilechlorotitanium(IV) tetrachloroferrate(III) [(C5H5)2Ti(Cl)NCCH3]+[FeCl4]- was investigated for antitumor properties against three solid experimental animal tumors (B16 melanoma, colon 38 adenocarcinoma, Lewis lung carcinosarcoma). The growth of all three tumors was inhibited significantly by the titanocene complex. Colon 38 carcinoma and Lewis lung carcinoma revealed to be more sensitive to the titanocene tetrachloroferrate derivative than solid B16 melanoma, whereby the growth development of the aforementioned tumors was suppressed by 70-76% of control tumor size to T/C ratios amounting to 24-30%. Bis(cyclopentadienyl)acetonitrilechlorotitanium(IV) tetrachloroferrate(III) is representative of ionic titanocene complexes which are generally distinguished by improved water solubility in comparison to neutral metallocene compounds.

Tumor inhibition by ferricenium complexes. Activity against some solid experimental tumors.

In the present study, the antitumor activity of some water-soluble ferricenium complexes [(C5H5)2Fe]+ X- (I, X- = [FeCl4]-; II, X- = 1/2[Cl3FeOFeCl3]2-; III, X- = [2,4,6-(NO2)3C6H2O]-; IV, X- = [CCl3COO]- 2CCl3COOH) was investigated against the solid, subcutanteously growing tumors sarcoma 180, B16 melanoma and colon 38 adenocarcinoma. Whereas, in the case of solid sarcoma 180, only marginal antitumor activity was observed for I-IV, the compounds effected growth inhibitions of solid B16 melanoma and colon 38 carcinoma by 35-60% and 50-73%, respectively, resulting in T/C ratios of 40-65% and 27-50%. In most tests, ferricenium trichloroacetate IV, followed by ferricenium mu-oxo-bis(trichloroferrate) II, were characterized by best antitumor properties against the tumor models investigated.

Ionic titanocene complexes: a new type of antitumor agent.

Five ionic cyclopentadienyltitanium (IV) derivatives were investigated for their activity against fluid Ehrlich ascites tumor. Four compounds were built up by the intact bis(cyclopentadienyl)titanium(IV) ("titanocene") unit, forming the cationic moiety together with two covalently bound ligands, with certain anions being bonded via electrostatic forces: the acetonitrile complex [(C5H5)2TiCl(NCCH3)]+[FeC14]- (I), the 2'2'-bipyridyl derivative [(C5H5)2Ti(bipy)]2+[CF3SO3]2 (II), the o-phenanthroline complex [(C5H5)2Ti(phen)]2+[CF3SO3]2 (III), and the N-methyl-o-aminothiophenolate derivative [(C5H5)2Ti[o-S(NACH3)C6H4]]+I- (IV). Another ionic cyclopentadienyltitanium derivative investigated was the five-coordinate bis(dithiolene) chelate (C5H5)Ti(1,2,4-S2C6H3CH3)2]-N(C2H5)4)+ (V), the cyclopentadienyltitanium moiety representing the anionic part of the complex salt. All complexes were ionic, salt-like compounds, distinguished by good water solubility. Whereas complexes I, III, and V, given at optimal dose levels, effected maximal cure rates of only 70%-80%, all animals were cured after receiving complexes II and IV at dose ranges of 200-220 and 240-300 mg/kg, respectively. The antitumor activity of complex I was confirmed against solid experimental tumor systems B16 melanoma, colon 38 carcinoma, and Lewis lung carcinosarcoma. Because of their improved solubility in water and pronounced antitumor activity (especially that of II and IV against fluid Ehrlich ascites tumor), ionic cyclopentadienyl titanium complexes are considered to be an interesting new type of antitumor agent.

Biological activity of organometallic bismuth compounds.

The chemical aspects of organometallic bismuth(III) compounds are discussed with respect to the stability of the metal-carbon sigma bond, their low dipole moments, and the limited solubility of these complexes in hydrophilic solvents. A new Bi heterocycle, which is of potential interest in terms of stability and solution behaviour, was shown to exist as an intermediate under the conditions in the mass spectrometer. Although generally bismuth organic compounds are extremely toxic, in the 1970s they became important as biocides and this is still being investigated. They have also been discussed as irritation causing chemical warfare agents. While their application in chemotherapy never became very widespread because antibiotics were discovered, in the last few years the antitumor activity of some derivatives has been reported.

Tumor inhibition by titanocene complexes: activity against sarcoma 180.

The antitumor activity of various titanocene derivatives was examined against ascitic and solid, subcutaneously growing sarcoma 180. The complexes investigated were two dihalide compounds, (C5H5)2TiCl2 (I) and (C5H5)2TiBr2 (II), two carboxylato complexes, (C5H5)2Ti (cis-OOCCH = CHCOOH)2(III) and (C5H5)2Ti(OOCCCl3)2(IV), and the p-aminothiophenolate hydrochloride (C5H5)2Ti(p-SC6H4NH3+Cl-)2(V). Against ascitic sarcoma 180, best results were obtained for I; an injection of 50 mg/kg resulted in the survival of 40-50% of the animals (ILS, 161-184%). A similar result was recorded for cis-diamminedichloroplatinum(II), whereas the compounds II-IV induced a maximum cure rate of 20% (ILS, 95-139%). Against solid sarcoma 180, triple injections of I-V caused reduction of mean tumor weight to 23-53% of control values, the dichloro complex I exhibiting most pronounced activity. These results clearly underline antitumor potency for titanocene complexes (C5H5)2TiX2 modified at the acido ligand X.