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Fast atom bombardment (FAB) and collision-induced dissociation (CID) tandem mass spectra of a series of novel pyrazolato-bridged dirhodium A-frame compounds provide structure confirmation and useful information concerning the structural dependence of lability, based upon fragmentation pathways. CID mass spectra indicate that FAB matrix- and beam-induced reduction chemistry can alter the energy and/or the structure of the precursor molecules. However, it appears that FAB matrix- and beam-induced oxidation chemistry does not do so detectably

Paramagnetic Rh23+complexes of the type [Rh2(μEE′)2(μ-Z)L2](PF6)2 (Z=3-methyl-5-trifluoromethylpyrazolate (mtmpz), 3,5-bis(trifluoromethyl)pyrazolate, (btmpz); EE′=bis(diphenylphosphino)methane (dppm), (diphenylarsino)(diphenylphosphino)methane (dapm); L=t-BuNC, CO) have been generated via electrochemical oxidation of the Rh22+ parent complexes [Rh2(μ-EE′)2(μ-Z) L2]PF6. Except for the diisocyanide complex containing dppm and btmpz, the complexes undergo isomerization which can be monitored by ESR spectroscopy down to −196 °C in CH2Cl2. For a given pyrazolate ligand the dppm complex undergoes isomerization at a lower temperature than the dapm complex, consistent with previous results that indicated that the dppm complex containing the 3,4,5- tribromopyrazolate (345Bpz) ligand did not isomerize down to −196 °C. Here we show that the low isomerization temperature for the complex containing the btmpz and dppm ligands is associated with the electronegativity of the CF3 substituents on the pyrazolate ring. The ESR spectrum of the complex that contains the mtmpz and dppm ligands indicates that both the high-temperature and low-temperature isomers are present at −196 °C, supporting the correlation between low isomerization temperature and electronegativity of the substituents on the pyrazolate ring.

PURPOSE: This phase III randomized trial compared two chemotherapy regimens, gemcitabine plus carboplatin and mitomycin, ifosfamide, and cisplatin, in chemotherapy-naive patients with advanced non-small-cell lung cancer (NSCLC). The regimens were compared with regard to effects on survival, response rates, toxicity, and quality of life. PATIENTS AND METHODS: Eligible patients had previously untreated stage IIIB or IV NSCLC suitable for cisplatin-based chemotherapy. Randomly assigned patients were to receive four cycles, each at 3-week intervals, of carboplatin area under the curve of 5 on day 1 plus gemcitabine 1,200 mg/m2 on days 1 and 8 (GCa) or mitomycin 6 mg/m2, ifosfamide 3g/m2, and cisplatin 50 mg/m2 on day 1 (MIC). RESULTS: Between February 1999 and August 2001, 422 patients (GCa, n = 212; MIC, n = 210) were randomly assigned in the United Kingdom. The majority of patients received the intended four cycles (GCa, 64%; MIC, 61%). There was a significant survival advantage for GCa compared with MIC (hazard ratio, 0.76; 95% CI, 0.61 to 0. 93; P = .008). Median survival was 10 months with GCa and 7.6 months with MIC (difference, 2.4 months; 95% CI, 1.0 to 4.0), and 1-year survival was 40% with GCa and 30% with MIC (difference, 10%; 95% CI, 3% to 18%). Overall response rates were similar (42% for GCa v 41% for MIC; P = .84). More thrombocytopenia occurred with GCa (P = .03), but this was not associated with increased hospital admission or fatality. GCa caused less nausea, vomiting, constipation, and alopecia and was associated with fewer admissions for administration and better quality of life. CONCLUSION: In patients with advanced NSCLC, GCa chemotherapy was shown to be a better-tolerated treatment that conferred a survival advantage over MIC.

The efficacy of m-nitrobenzyl alcohol (NBA) as a solvent (matrix) for fast atom bombardment (FAB) mass spectrometry of a group of pyrazolate-bridged dirhodium A-frame complexes has been assessed. Although NBA is frequently used to mitigate the formation of artifacts in FAB/MS of organometallics and other materials susceptible to bombardment-induced reactions, substantial evidence indicates that such reactions cause the formation of artifacts in the spectra obtained here. Parallel absorption spectroscopic studies have established that NBA is capable of inducing both oxidation and reduction reactions independent of ion bombardment, depending on analyte reduction half-wave potential (E12). From the known electrochemistry of the complexes studied, it can be estimated that 1020 Mv > E12 > 500 mV for the reaction of NBA serving as a reducing agent, while 500 mV > E12 > 424 mV for the reduction potential of NBA. However, in the presence of bombardment the former E12 must be at least as low as 356 mV, and the latter E12 must be at least as high as 1188 mV. The kinetics of redox reactions involving NBA, and therefore their influence on the appearance of FAB mass spectra, will be highly sample-dependent. However, this study illustrates an important potential role for redox reactions when NBA is used as a solvent, especially in the presence of bombardment in FAB/MS. Although analyte reaction products could be identified, substantial efforts aimed at identifying NBA oxidation and reduction products did not yield any definitive results due to the complexity of product mixtures.

Preparation, reactivite et structure de [Rh 2 (μ-dam) 2 (CO) 2 (μ-35 mpz)]PF 6 et [Rh 2 (μ-dam) 2 (CO) 2 (μ-35 mpz)] +

Paramagnetic complexes of the type (Rh{sub 2}({mu}-EE{prime}){sub 2}(t-BuNC){sub 2}({mu}-Z))(PF{sub 6}){sub 2} (EE{prime} = bis(diphenylphosphino)methane (dppm), (diphenylarsino)(diphenylphosphino)methane (dapm), bis(diphenylarsino)methane (dpam); Z = pyrazolate (pz), 4-methylpyrazolate (4mpz), 3,5-dimethylpyrazolate (35mpz), 4-bromo-3,5-dimethylpyrazolate (4B35mpz), 3,4,5-tribromopyrazolate (345Bpz)) containing the Rh{sub 2}{sup 3+} core have been prepared via controlled-potential electrolysis of the parent Rh{sub 2}{sup 2+} species (Rh{sub 2}({mu}-EE{prime}){sub 2}(t-BuNC){sub 2}({mu}-Z))(PF{sub 6}). The Rh{sub 2}{sup 2+} diisocyanide complexes and analogous dicarbonyl complexes have cyclic voltammograms that exhibit a quasi-reversible wave followed by an irreversible or a second quasi-reversible wave. The E{sub {1/2}} values for the couple at less positive potentials are in the order dppm < dapm < dpam for analogous diisocyanide and dicarbonyl complexes; thus, the stabilities of the Rh{sub 2}{sup 3+} paramagnetic complexes toward reduction are in the order dpam < dapm < dppm. UV-vis spectroscopy has been sued to demonstrate that electron transfer occurs between Rh{sub 2}{sup 2+} and Rh{sub 2}{sup 3+} species containing different EE{prime} ligands when the initial Rh{sub 2}{sup 3+} species is the less stable one of the two possible Rh{sub 2}{sup 3+} species. The ESR spectra for the Rh{sub 2}{sup 3+} diisocyanide species in 4:1 CG{sub 2}Cl{sub 2}/toluene at room temperature and in frozen solutions are reported. The frozen-solution spectramore » at temperatures above -196{degree}C indicate the existence of two forms of the complex, a green {alpha} form and a red {beta} form, and the temperatures at which the {alpha} to {beta} isomerization occurs is in the order ddpm < dapm < dpam for a given pyrazolate. 20 refs., 7 figs., 4 tabs.« less

The crystal structure of [Rh 2 (dppm) 2 (/gm-OH)- (CO) 2 ] [PF 6 ]·(CH 3 ) 2 CO has been determined. The crystal and structure data are, M r = 1250.7, mono- clinic, P 2 1 / n , a = 10.165(3), b = 21.084(4), c = 25.85(1) A, β = 95.69(3)°, V = 5513(3) A 3 , Z = 4, D m (295 K) = 1.48, D x = 1.51 g cm −3 , Mo Kα, λ = 0.71069 A, μ = 5.03 cm −1 , F (000) = 2348, R = 0.0433, R w = 0.0462, 6257 observed reflections I >3/gs (I) . This molecule was found to be hydrogen- bonded to an acetone molecule in the lattice and has a Rh⋯Rh separation of 3.139(1) A, and a Rh(1) O(3)Rh(2) angle of 99.1(1)°. No other unusual structural features were observed.

Results of phase equilibria studies are reported for the neon–argon system at temperatures from 87.34 to 123.83°K and pressures to 3880 atm. These results, combined with those of earlier studies, provide a complete description, partly quantitative and partly qualitative, of the lines and surfaces comprising an important segment of the three‐dimensional, pressure–temperature–composition, phase diagram for neon–argon. A three‐dimensional sketch of the diagram is used to show the important phase boundary lines and the qualitative features in the region of transition from fluid to solid at high pressures. The relevance of these studies to problems of deep atmosphere structures in the outer planets is briefly discussed.

Preparation, reactivite et structure de [Rh 2 (μ-dam) 2 (CO) 2 (μ-35 mpz)]PF 6 et [Rh 2 (μ-dam) 2 (CO) 2 (μ-35 mpz)] +

The crystal structure of [Rh 2 (dppm) 2 (/gm-OH)- (CO) 2 ] [PF 6 ]·(CH 3 ) 2 CO has been determined. The crystal and structure data are, M r = 1250.7, mono- clinic, P 2 1 / n , a = 10.165(3), b = 21.084(4), c = 25.85(1) A, β = 95.69(3)°, V = 5513(3) A 3 , Z = 4, D m (295 K) = 1.48, D x = 1.51 g cm −3 , Mo Kα, λ = 0.71069 A, μ = 5.03 cm −1 , F (000) = 2348, R = 0.0433, R w = 0.0462, 6257 observed reflections I >3/gs (I) . This molecule was found to be hydrogen- bonded to an acetone molecule in the lattice and has a Rh⋯Rh separation of 3.139(1) A, and a Rh(1) O(3)Rh(2) angle of 99.1(1)°. No other unusual structural features were observed.