The binding of eosin-labeled subunit δ to the isolated chloroplast ATPase, CF1, as revealed by rotational diffusion in solution

We investigated the binding of subunit δ to solubilized chloroplast ATPase. Purified δ was covalently labeled with eosin 5-isothiocyanate and its rotational correlation time was determined by a photoselection technique as a function of added CF₁ (containing δ) and of CF₁(−δ) (lacking δ). In aqueous buffer the rotational correlation time of labeled δ was 33 ns. This is compatible with a rather elongated shape with the dimensions 2b = 100 Å/2a = 28 Å. Binding of δ to CF₁ decreased the rotational correlation time about 10-fold. The result was a biphasic decay of the laser flash-induced absorption anisotropy which was analyzed to yield the proportion of δ (bound to CF₁) relative to δ (free). CF₁(−δ), which completely lacked the δ-subunit, bound one δ (mol/mol) with high affinity (K_d ≈ 100 nM) and at least another δ with about 20-fold lower affinity. The δ-containing CF₁, revealed only the low-affinity site(s) for δ. This was compatible with a 1:1 stoichiometry of δ in isolated CF₁.     

Ligand induced P---H bond formation and a comparison of the reactivity of two isomers of the carbonyl hydride [Pt2(μ-PBu2)2(H)(CO)(PBu2H)]CF3SO3

The Pt₂ ^(II) isomeric terminal hydrides [(CO)(H)Pt(μ-PBu^t ₂)₂Pt(PBu^t ₂H)]CF₃SO₃ (1a), and [(CO)Pt(μ-PBu^t ₂)₂Pt(PBu^t ₂H)(H)]CF₃SO₃ (1b), react rapidly with 1 atm of carbon monoxide to give the same mixture of two isomers of the Pt₂ ^(I) dicarbonyl [Pt₂(μ-PBu^t ₂)(CO)₂(PBu^t ₂H)₂]CF₃SO₃ (3-Pt); the solid state structure of the isomer bearing the carbonyl ligands pseudo-trans to the bridging phosphide was solved by X-ray diffraction. A remarkable difference was instead found between the reactivity of 1a and 1b towards carbon disulfide or isoprene. In both cases 1b reacts slowly to afford [Pt₂(μ-PBu^t ₂)(μ,η²,η²-CS₂)(PBu^t ₂H)₂]CF₃SO₃ (4-Pt), and [Pt₂(μ-PBu^t ₂)(μ,η²,η²-isoprene) (PBu^t ₂H)₂]CF₃SO₃ (6-Pt), respectively. In the same experimental conditions, 1a is totally inert. A common mechanism, proceeding through the preassociation of the incoming ligand followed by the P---H bond formation between one of the bridging P atoms and the hydride ligand, has been suggested for these reactions.     

The synthesis of the tripodal phosphine CH3C{CH2P(m-CF3C6H4)2}3 and its rhodium coordination chemistry

The new tripodal phosphine CH₃C{CH₂P(m-CF₃C₆H₄)₂}₃, CF₃PPP, was prepared by reacting CH₃C(CH₂Br)₃ with Li⁺P(m-CF₃C₆H₄)₂⁻, the latter being best obtained by adding Li⁺NⁱPr₂⁻ to PH(m-CF₃C₆H₄)₂. The rhodium complexes [RhCl(CO)(CF₃PPP)], [Rh(LL)(CF₃PPP)](CF₃SO₃) (LL = 2 CO or NBD), [RhX₃(CF₃PPP)], [RhX(MeCN)₃(CF₃PPP)](CF₃SO₃)₂ (X = H and Cl), [RhCl₂(MeCN)(CF₃PPP)](CF₃SO₃) and [Rh(MeCN)₃(CF₃PPP)](CF₃SO₃)₃ were prepared and characterized. The X-ray crystal structure of [Rh(NBD)(CF₃PPP)](CF₃SO₃) is reported. The lower oxygen sensitivity of the CF₃PPP rhodium(I) complexes, relative to the corresponding species with the parent ligand CH₃C(CH₂PPh₂)₃, is attributed to the higher effective nuclear charge on the metal centers caused by the presence of the six CF₃ substituents on the terdentate phosphine. A similar effect may be responsible for the easier hydrolysis of the CF₃PPP-containing, cationic rhodium(III) complexes relative to the corresponding compounds of the parent ligand.     

Hetero-polynuclear complexes containing bridging diphenylphosphino-alkenes and -alkynes. The crystal structure of an Rh2{μ−ν:ν−P(Ph2) (CH2)3C≡CR}Co2 complex

The phosphinoalkenes Ph₂P(CH₂)_nCH=CH₂ (n= 1, 2, 3) and phosphinoalkynes Ph₂P(CH₂)_n C≡CR (R = H, N = 2, 3; R = CH₃, N = 1) have been prepared and reacted with the dirhodium complex (η−C₅H₅)₂Rh₂(μ−CO) (μ−η²−CF₃C₂CF₃). Six new complexes of the type (ν−C₅H₅)₂(Rh₂(CO) (μ−η¹:η¹−CF₃C₂CF₃)L, where L is a P-coordinated phosphinoalkene, or phosphinoalkyne have been isolated and fully characterized; the carbonyl and phosphine ligands are predominantly trans on the Rh---Rh bond, but there is spectroscopic evidence that a small amount of the cis-isomer is formed also. Treatment of the dirhodium-phosphinoalkene complexes with (η−CH₃C₅H₄)Mn(CO)₂thf resulted in coordination of the manganese to the alkene function. The Rh₂---Mn complex [(η−C₅H₅)₂Rh₂(CO) (μ−η¹:η¹−CF₃C₂CF₃) {Ph₂P(CH₂)₃CH=CH₂} (η−CH₃C₅H₄)Mn(CO)₂] was fully characterized. Simi treatment of the dirhodium-phosphinoalkyne complexes with Co₂(CO)₈ resulted in the coordination of Co₂(CO)₆ to the alkyne function. The Rh₂---Co₂ complex [(η−C₅H₅)₂Rh₂(CO) (μ−η¹:η¹−CF₃C₂CF₃) {Ph₂PCH₂C≡CCH₃}Co₂(CO)₂], C₃₇H₂₅Co₂F₆O₇PRh₂, was fully characteriz spectroscopically, and the molecular structure of this complex was determined by a single crystal X-ray diffraction study. It is triclinic, space group (C_i¹, No. 2) with a = 18.454(6), B = 11.418(3), C = 10.124(3) Å, = 112.16(2), β = 102.34(3), γ = 91.62(3)°, Z = 2. Conventional R on |F| was 0.052 fo observed (I > 3σ(I)) reflections. The Rh₂ and Co₂ parts of the molecule are distinct, the carbonyl and phosphine are mutually trans on the Rh---Rh bond, and the orientations of the alkynes are parallel for Rh₂ and perpendicular for Co₂. Attempts to induce Rh₂Co₂ cluster formation were unsuccessful.     

Ruthenium(III) maltolato-nitroimidazole complexes: synthesis and biological activity

The Ru(III) metronidazole-maltolato and -ethylmaltolato complexes, trans-[RuL₂(metro)₂]CF₃SO₃ (L = ma (1a) or etma (1b)), have been synthesized and tested for potential anti-tumour activity against the human breast cancer cell line MDA-MB-435S using a so-called MTT assay in phosphate-buffered saline; ma = 3-hydroxy-2-methylpyran-4-onato, etma = 2-ethyl-3-hydroxypyran-4-onato, metro = 2-methyl-5-nitro-1H-imidazole-1-ethanol (metronidazole); MTT = 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. The complexes exhibit lower IC₅₀ values than our previously reported Ru(III) tris-maltolato and -ethylmaltolato complexes [D.C. Kennedy, A. Wu, B.O. Patrick, B.R. James, Inorg. Chem. 44 (2005) 6529–6535]. An improved synthetic route to the 2-nitroimidazole EF5 (2-(2-nitro-1-H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl)acetamide) is reported, as well as a related synthesis of a 3-nitro-1,2,4-triazole derivative of EF5, triF5 (2-(3-nitro-1-H-triazol-1-yl)-N-(2,2,3,3,3- pentafluoropropyl)acetamide). The complexes [RuL₂(EF5)₂]CF₃SO₃ (4a and 4b) and [Ru(ma)₂(triF5)₂]CF₃SO₃ (5) were prepared from the [RuL₂(EtOH)₂]CF₃SO₃ complexes (3a and 3b); IC₅₀ values for 3–5 are high. Data on the uptake of Ru by the cells are also reported. The complexes were characterized generally by all or some of the following methods: elemental analyses, NMR, IR and mass spectroscopies, conductivity, and cyclic voltammetry; complexes 1a and 1b were also analyzed by X-ray crystallography.     

Alkene rotation in [Ru(η-C5H5) (L2) (η-alkene][CF3SO3] with L2 = iPr- or pTol-diazabutadiene. X-ray crystal structure of [Ru(η-C5H5(pTol-DAB) (η-ethene][CF3SO3]

Reaction of RuCl(η⁵-C₅H₅(pTol-DAB) with AgOTf (OTf = CF₃SO₃) in CH₂Cl₂ or THF and subsequent addition of L′ (L′ = ethene (a), dimethyl fumarate (b), fumaronitrile (c) or CO (d) led to the ionic complexes [Ru(η⁵-C₅H₅)(pTol-DAB)(L′)][OTf] 2a, 2b and 2d and [Ru(η⁵-C₅H₅)(pTol-DAB)(fumarontrile-N)][OTf] 5c. With the use of resonance Raman spectroscopy, the intense absorption bands of the complexes have been assigned to MLCT transitions to the iPr-DAB ligand. The X-ray structure determination of [Ru(η⁵-C₅H₅)(pTol-DAB)(η²-ethene)][CF₃SO₃] (2a) has been carried out. Crystal data for 2a: monoclinic, space group P2₁/n with A = 10.840(1), b = 16.639(1), C = 14.463(2) Å, β = 109.6(1)°, V = 2465.6(5) ų, Z = 4. Complex 2a has a piano stool structure, with the Cp ring η⁵-bonded, the pTol-DAB ligand σN, σN′ bonded (Ru-N distances 2.052(4) and 2.055(4) Å), and the ethene η²-bonded to the ruthenium center (Ru-C distances 2.217(9) and 2.206(8) Å). The C = C bond of the ethene is almost coplanar with the plane of the Cp ring, and the angle between the plane of the Cp ring and the double of the ethene is 1.8(0.2)°. The reaction of [RuCl(η⁵-C₅H₅)(PPh)₃ with AgOTf and ligands L′ = a and d led to [Ru(η⁵-C₅H₅)(PPh₃)₂(L′)]OTf] (3a) and (3d), respectively. By variable temperature NMR spectroscopy the rottional barrier of ethene (a), dimethyl fumarate (b and fumaronitrile (c) in complexes [Ru(η⁵-C₅H₅)(L₂)(η²-alkene][OTf] with L₂ = iPr-DAB (a, 1b, 1c), pTol-DAB (2a, 2b) and L = PPh₃ (3a) was determined. For 1a, 1b and 2b the barrier is 41.5±0.5, 62±1 and 59±1 kJ mol⁻¹, respectively. The intermediate exchange could not be reached for 1c, and the ΔG^# was estimated to be at least 61 kJ mol⁻. For 2a and 3a the slow exchange could not be reached. The rotational barrier for 2a was estimated to be 40 kJ mol⁻. The rotational barier for methyl propiolate (HC≡CC(O)OCH₃) (k) in complex [Ru(η⁵-C₅H₅)(iPr-DAB) η²-HC≡CC(O)OCH₃)][OTf] (1k) is 45.3±0.2 kJ mol⁻¹. The collected data show that the barrier of rotational of the alkene in complexes 1a, 2a, 1b, 2b and 1c does not correlate with the strength of the metal-alkene interaction in the ground state.     

N-Ethylmaleimide inhibition of the catalytic activities of the Dunaliella salina coupling factor 1 (CF1) and the restoration of the inhibition of the CF1 ATPase activity by N-ethylmaleimide

The sensitivity of the catalytic activities of the D. salina chloroplast coupling factor 1 (CF₁) to chemical modification by N-ethylmaleimide has been investigated. (i) When D. salina thylakoid membranes are treated with N-ethylmaleimide, both photophosphorylation and the inducible CF₁ ATPase activity are partially (approx. 60%) inhibited. The inhibition of both activities does not require the presence of a proton-motive force, and the inhibition of photophosphorylation is directly related to the N-ethylmaleimide-covalent modification of CF₁ as shown by (a) the time-course for the inhibition and (b) the maximal extent of inhibition. (ii) Treatment of the purified, latent, D. salina CF₁ with low concentrations of N-ethylmaleimide also results in the partial (approx. 60%) inhibition of the inducible ATPase activity (I₅₀ ≈ 50 μM). The inhibition does not require the presence of the chemical modifier during the activation of the enzyme. (iii) N-ethylmaleimide-induced inhibition of the ATPase activity of either membrane-bound or solubilized CF₁ is partially reversed by either (a) prolonged incubation at low concentrations of N-ethylmaleimide or (b) short incubation times at high concentrations of N-ethylmaleimide. The results are interpreted as indicating multiple binding sites on the D. salina CF₁ that have different rates of reactivity with N-ethylmaleimide. Those sites (or site) that react rapidly with N-ethylmaleimide cause(s) an inhibition of both ATP synthase and ATPase activities, whereas those sites (or site) that react more slowly partially restore(s) the original-ATPase activity. The effects of N-ethylmaleimide on the catalytic activity of D. salina CF₁ are probably mediated by N-ethylmaleimide-induced conformational changes of the enzyme.     

Labeling studies of some carbonylation reactions of styrene with cationic palladium complexes

The dicarbonylation reaction of E-β-deuteriostyrene to syndiotactic poly(1-oxo-2-phenyltrimethylene) as well as to dimethyl-2-phenylbutanedioate and dimethyl-2,5-diphenyl-4-oxoheptanedioate using Pd(CF₃COO)₂/2,2′-bipyridine as the catalyst precursor in the presence of 1,4-benzoquinone in methanol takes place stereospecifically in a syn-fashion with complete retention of the label. The same result was found for the dicarbonylation to dimethyl 2-phenylbutanedioate catalyzed by [Pd(CF₃COO)₂(Diop)]. In the absence of the oxidant the latter catalytic system produces methyl 2- and 3-phenylpropionates for which some scrambling of deuterium is observed when using either -deuteriostyrene or CH₃OD as the labeled substrate. [Pd(CH₃CN)₄][BF₄]₂ modified with different ligands catalyses the formation of E-1,5-diphenylpent-1-en-3-one or of E-1,4-diphenylpent-1-en-3-one in tetrahydrofuran as the solvent. The label distribution using E-β-deuteriostyrene as the substrate (or styrene in the presence of dideuterium) suggests that in the synthesis of ketones catalyzed by [Pd(p-CH₃C₆H₄SO₃)₂(Dppp)]·2H₂O the regioselectivity of the first inserted olefin unit does not determine the ketone regioisomer; rather which regioisomeric product preferentially forms depends on the rate of carbon monoxide insertion in either the branched or linear metal-hydrocarbyl intermediate. β-Hydrogen elimination is very rapid both after the first and the second olefin insertion.     

Rhodium(I) complexes of the type [TpRh(LL)] (LL = 2 CO, NBD, COD) with trifluoromethyl substituted tris (pyrazolyl) borate ligands and their dynamic behaviour in solution. The X-ray crystal structure of TpRh(CO)2

Three seriesof Rh(I) complexes of the type Tp^3R,5RRh(LL), with LL = 2 CO (1), norbornadiene (NBD) (2) and 1,5-cyclooctadiene (COD) (3) and the tris (pyrazolyl)borate (Tp) ligands 3R=5R=Me (a), 3R=CF₃5R=Me (b); and 3R=5R=CF₃ (c) were synthesized and fully characterized by IR and multinuclear NMR spectroscopy. Three isomeric forms were identified in solutions of these complexes: two square-planar isomers with a κ²-Tp³R,5R ligand, the uncoordinated pyrazolyl ring occupying either an equatorial position (type A), or an axial position (type B), and a five-coordinate species with a κ³, Tp³R,5R ligand (type C). In the carbonyl complexes 1 the dynamic equilibria between these isomers are solvent dependent. Interestingly, solutions of complex 1c contained all three isomers simultaneously. ¹⁰³Rh and ¹³C NMR spectral studies indicate that the NBD compounds, 2, preferentially form square-planar complexes when Tp^CF₃,Me and Tp^CF₃,CF₃ are present, while for the COD complexes, 3, square-planar complexes are preferred for all three Tp-type ligands. The X-ray structure of Tp^CF₃,MeRh(CO)₂ (1b) was determined (spacce group C2/ c,a = 21.271(9), B = 11.004(3), C = 21.563(9) Å, β = 114.93(3)°, V=4577(3) ų, Z = 8, R = 3.41, R_w = 4.70). Its structure is of type B, with the third pyrazolyl ring axially placed, the N(4) being almost directly above the Rh atom but exerting only a weak Rh-N interaction.     

Mono-η complexes of chromium(II) and chromium(0). Electron demanding substituents, structural and spectroscopic data comparisons

Using thermal and photochemical methods a series of new chromium complexes has been prepared: (ν⁶-p-C₆H₄F₂)Cr(CO)₃; (ν⁶-C₆H₅CF₃)Cr(CO)₃; [m-C₆H₄(CF₃)₂]Cr(CO)₃; (ν⁶-C₆H₅F)Cr(CO)₂H(SiCl₃); (ν⁶-C₆H₅F)Cr(CO)₂(SiCl₃)₂; (p-C₆H₄F₂)Cr(CO)₂-H(SiCl₃); (C₆H₅CF₃)Cr(CO)₂H(SiCl₃(p-C₆H₄F₂)Cr(CO)₂(SiCl₃)₂; C₆H₅CF₃)Cr(CO)₂(SiCl₃)₂; [m-C₆H₄(CF₃)₂]Cr(CO)₂-H(SiCl₃); [m-C₆H₄(CF₃)₂]Cr(CO)₂(SiCl₃)₂. Two compounds were structurally characterized by X-ray diffraction. These data combined with IR and ¹H NMR have allowed assessment of some of the electronic and steric effects. The Cr-arene bond is considerably longer in the Cr(II) derivatives than in the Cr(0) species. Also the Cr center, as might be expected, is less electron rich in the Cr(II) dicarbonyl disilyl derivatives. The ν⁶-p-C₆H₄F₂ ligands are slightly folded so that the C---F carbons are moved further away from the Cr center. Comparison of structural and electronic effects is made with a series of similar chromium compounds reported in the literature. These new (arene)Cr(II) derivatives possess more labile ν⁶-arene ligands, which promise a rich chemistry at the chromium center.     

Synthesis and characterization of SrCu2(O2CR)3(bdmap)3 and Bi2(O2CCH3)4(bdmap)2(H2O) (R = CH3, CF3; bdmap = 1,3-bis(dimethylamino)-2-propanolato)

New mixed metal complexes SrCu₂(O₂CR)₃(bdmap)₃ (R = CF₃ (1a), CH₃ (1b)) and a new dinuclear bismuth complex Bi₂(O₂CCH₃)₄(bdmap)₂(H₂O) (2) have been synthesized. Their crystal structures have been determined by single-crystal X-ray diffraction analyses. Thermal decomposition behaviors of these complexes have been examined by TGA and X-ray powder diffraction analyses. While compound 1a decomposes to SrF₂ and CuO at about 380°C, compound 1b decomposes to the corresponding oxides above 800°C. Compound 2 decomposes cleanly to Bi₂O₃ at 330°C. The magnetism of 1a was examined by the measurement of susceptibility from 5–300 K. Theoretical fitting for the susceptibility data revealed that 1a is an antiferromagnetically coupled system with g = 2.012(7), −2J = 34.0(8) cm⁻¹. Crystal data for 1a: C₂₇H₅₁N₆O₉F₉Cu₂Sr/THF, monoclinic space group P2₁/m, A = 10.708(6), B = 15.20(1), C = 15.404(7) Å, β = 107.94(4)°, V = 2386(2) ų, Z = 2; for 1b: C₂₇H₆₀N₆O₉Cu₂Sr/THF, orthorhombic space group Pbcn, A = 19.164(9), B = 26.829(8), C = 17.240(9) Å, V = 8864(5) ų, Z = 8; for 2: C₂₂H₄₈O₁₁N₄Bi₂, monoclinic space group P2₁/c, A = 17.614(9), B = 10.741(3), C = 18.910(7) Å, β = 109.99(3)°, V = 3362(2) ų, Z = 4.     

Guanosine and formycin triphosphates bind at non-catalytic nucleotide binding sites of CF1 ATPase and inhibit ATP hydrolysis

Guanosine triphosphate and formycin triphosphate (FTP) in the presence of excess Mg²⁺ can bind to empty non-catalytic sites of spinach chloroplast ATPase (CF₁). This results in a greatly reduced capacity for ATP hydrolysis compared to the enzyme with non-catalytic sites filled with ATP. With two GTP bound at non-catalytic sites the inhibition is about 90%; with two FTP bound about 80% inhibition is obtained. Binding and release of the nucleotides from the non-catalytic sites are relatively slow processes. Exposure of CF₁ with one or two empty non-catalytic sites to 5–10 μM FTP or GTP for 15 min suffices for about 50% of the maximum inhibition. Reactivation of CF₁ after exposure to higher FTP or GTP concentrations requires long exposure to 2 μM EDTA. The findings show that, contrary to previous assumptions, GTP can bind tightly to non-catalytic sites of CF₁. They suggest that the presence of adenine nucleotides at non-catalytic sites might be essential for high catalytic capacity of the F₁ ATPases.     

Dioxo-molybdenum(VI) and -tungsten(VI) BINOL and alkoxide complexes: Synthesis and catalysis in sulfoxidation, olefin epoxidation and hydrosilylation of carbonyl groups

The reaction of MoO₂(mes)₂ with S-H₂BINOL (mes = 2,4,6-Me₃C₆H₂; H₂BINOL = 1,1′-bi-2-naphthol) and (CF₃)₂MeCOH in THF yielded the novel dioxo-molybdenum(VI) complexes MoO₂(S-BINOL)(THF)₂ and MoO₂[OCMe(CF₃)₂]₂(THF), respectively. Similar tungsten derivatives WO₂(S-BINOL)(THF) and WO₂[OCMe(CF₃)₂]₂(THF) have been prepared by the reaction of WO₂Cl₂(DME) with the corresponding lithium salts of BINOL and 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, respectively. Catalytic experiments have shown that MoO₂(S-BINOL)(THF)₂ is an active catalyst in the sulfoxidation of methyl phenyl sulfide and in the epoxidation of cis-cyclooctene with tert-butylhydroperoxide, under mild conditions. The BINOL complex was, however, not found to be enantioselective. In addition, the catalytic activity of the molybdenum species MoO₂(S-BINOL)(THF)₂ and MoO₂[OCMe(CF₃)₂]₂(THF) in the hydrosilylation of carbonyl groups has been explored.     

Nitrogen, sulfur and oxygen donor adducts with copper(II) complexes of antitumor 2-formylpyridinethiosemicarbazone analogs: Physicochemical and cytotoxic studies

The preparation of N-, S- and O-donor ligand adducts with CuX⁺(HX=6-methyl-2-formylpyridinethiosemicarbazone (6HL); 2-formylpyridine-2^′-methylthiosemicarbazone (2′L); 2-formylpyridine-4′-methylthiosemicarbazone (4′HL)) is described. The N-donors, 2,2′-bipyridyl (bipy), 4-dimethylaminopyridine (dmap) give the complexes [Cu(6L)(bipy)]PF₆, [Cu(6L)(bipy)]Cl·5H₂O, [Cu(4′L)(bipy)]PF₆, [Cu(6L)(dmap)₂]PF₆·2.5 H₂O and [Cu(4′L)(dmap)₂]PF₆·H₂O which have been characterized by physical and spectroscopic techniques. Pentafluorothiophenolate (pftp) gives S-donor complexes [CuX(pftp)] (X=6L and 4′L) and thiolato co-ordination is proposed on the basis of spectroscopic evidence. Paratritylphenolate (ptp) and HPO²⁻₄ give O-donor complexes [Cu(6L)(ptp)], [Cu(4′L)(ptp)], [{Cu(6L)}₂HPO₄]·4H₂O, and [{Cu(4^′L)}₂HPO₄]·5H₂O which have been characterized by physical and spectroscopic techniques, as have the precursor complexes [Cu(6L)(CH₃COO)]·H₂O, [Cu(4′L)(CH₃COO)], Cu(6HL)(CF₃COO)](CF₃COO)·0.5H₂O, [Cu(4′HL)(CF₃COO)](CF₃COO), [Cu(2′L)Cl₂] and [Cu(2′L)(NO₃)₂]. Protonation constants for the ligands and some of their complexes have been determined. 2-Formylpyridinethiosemicarbazone (HL) complexes of silver, gold, zinc, mercury, cadmium and lead are also discussed. Cytotoxicity against the human tumor cell line HCT-8 and antiviral data for selected compounds are presented.     

Synthesis, spectroscopic properties and X-ray crystal structures of two dinuclear alkoxo-bridged copper(II) compounds with the ligand bis(1-methyl-2-benzimidazolyl) propane. A unique alkoxo-bridged Cu(II) dinuclear compound with an additional bidentate bridging triflate anion

Based on the new ligand bis(1-methyl-2-benzimidazolyl) propane (abbreviated as mtbz) several new copper(II) coordination compounds have been prepared and characterized structurally and spectroscopically. Two representative compounds, i.e. [Cu₂(mtbz)₂(CH₃)₂- (CF₃SO₃)](CF₃SO₃) (1) and [Cu₂(mtbz)₂(CH₃O)₂](ClO₄)₂ (4) were characterized structurally by X-ray diffraction. Crystal data for 1: monoclinic, space group P2₁/c, a=13.6585(5), B=39.981(3), C=20.919(1) Å, β=125.98(1)°, Z=8. Crystal data for 4: monoclinic, space group P2₁/c, a=13.115(2), B=9.523(2), C=17.908(4) Å, β=111.71(1)°, Z=2. Structures 1 and 4 each consist of a dinuclear unit with bridging methoxo groups and one ligand linked to each copper via an N atom. Structure 1 (which consists of two dinuclear, crystallographically independent, but chemically identical units) has the two copper atoms bridged by a triflate anion, providing each copper atom a square-pyramidal coordination, while the copper atoms in structure 4 have an almost a square-planar geometry. The Cu---Cu distances (Å) within the dinuclear units are: 1, 2.9775(13), 2.9751(13); 4, 2.9872(16); the Cu---O---Cu bridging angles (°) are: 1, 101.7(3), 101.7(3), 100.9(3), 102.1(3); 4, 103.2(2). The mid-IR section focused on the vibrations of the triflate anion reveals interesting results concerning the assignments of that anion related to the v_as(S---O) band. Characteristic Cu---O vibrations in the far-IR section were found at 386 and 230 cm⁻¹ for the methoxo-bridged and 454 and 332 cm⁻¹ for the ethoxo-bridged compounds. These dinuclear species are EPR silent, and only a weak signal of monomeric impurities is observed. They also show a diamagnetic behavior below room temperature.     

ADP binding and ATP synthesis by reconstituted H-ATPase from chloroplasts

The H⁺-ATPase from chloroplasts, CF₀F₁, was isolated, purified and reconstituted into asolectin liposomes. The enzyme was brought either into the oxidized state or into the reduced state, and the rate of ATP synthesis was measured after energisation of the proteoliposomes with an acid—base transition ΔpH (pH_in = 5.0, pH_out = 8.5) and a K⁺/valinomycin diffusion potential, Δφ (K⁺_in = 0.6 mM, K⁺_out = 60 mM). A rate of 250 s⁻¹ was observed with the reduced enzyme (85 s⁻¹ in the absence of Δφ). A rate of 50 s⁻¹ was observed with the oxidized enzyme under the same conditions (15 s⁻¹ in the absence of Δφ). The reconstituted enzyme contained 2 ATP_bound per CF₀F₁ and 1 ADP_bound per CF₀F₁. Upon energisation the enzyme was activated and 0.9 ADP per CF₀F₁, was released. Binding of ADP to the active reduced enzyme was observed under different conditions. In the absence of phosphate the rate constant for ADP binding was 10⁵ M⁻¹·s⁻¹ under energized and de-energized conditions. In the presence of phosphate the rate of ADP binding drastically increased under energized conditions, and strongly decreased under de-energized conditions.     

Interaction of the chloroplast ATP synthetase with the photoreactive nucleotide 3′-O-(4-benzoyl)benzoyl adenosine 5''-diphosphate

The photoreactive nucleotide 3'-O-(4-benzoyl)benzoyl ADP (BzADP) is not a substrate for photophosphorylation but is a strong competitive inhibitor (K_i 2-25μM) with respect to ADP and ATP in photophosphorylation or ATP hydrolysis and P_i-ATP exchange reactions, respectively. The analog binds tightly to the membrane-bound CF₁, competes with the right binding of ADP, and prevents the inactivation of the enzyme by tight binding of ADP. Upon irradiation with long wavelength ultraviolet light, the tightly bound BzADP becomes covalently attached to both the - and β-subunits of the enzyme.     

Synthesis and characterization of homologous nickel(II) and palladium(II) complexes with biphosphine monoxide ligands Ph2P(CH2)nP(O)Ph2 (n = 1–3) and pTol2P(CH2)P(O)pTol2

A series of cationic nickel complexes [(η³-methally)Ni(PP(O))]SbF₆ (1–4) [PP(O) = Ph₂P(CH₂)P(O)Ph₂ (dppmO) (1), Ph₂P(CH₂)₂P(O)Ph₂ (dppeO) (2), Ph₂P(CH₂)₃P(O)Ph₂ (dpppO) (3), pTol₂P(CH₂)P(O)pTol₂ (dtolpmO) (4)] has been synthesized in good yields by treatment of [(η³-methally)NiBr]₂ with biphosphine monoxides and AgSbF₆. The ligands are coordinated in a bidentate way. Starting from [(η³-all)PdI]₂ the cationic complexes [(η³-all)PP(O))]Y (8–14). [PP(O) = dppmO, dppeO, dpppO, dtolpmO;Y = BF₄, SbF₆, CF₃SO₃, pTolSO₃] were synthesized in good yields. The coordination mode of the ligand is dependent on the backbone and the anion, revealing a monodentate coordination with dppmO for stronger coordinating anions. The intermediates [(η³-all)Pd(I)(PP(O)-κ¹-P)] (5–7) [PP(O) = dppmO (5), dppeO (6), dtolpmO (7)] were isolated and characterized. Neutral methyl complexes [(Cl)(Me)Pd(PP(O))] (15–18). [PP(O) = dppmO (15), dppeO (16), dpppO (17), dtolpmO (18)] can easily be obtained in high yields starting from [(cod)PdCl₂]. For dppmO two different routes are presented. The structure of [(Me)(Cl)Pd{;Ph₂P(CH₂-P(O)Ph₂-κ²-P,O};] · CH₂Cl₂ (15) with the chlorine atom trans to phosphorus was determined by X-ray diffraction.     

The synthesis and reactivity of electrophilic iridium (III) complexes containing bis (diphenylphosphino) ethane

The complex Ir(CH₃) (CO) (CF₃SO₃)₂ (dppe) (1) has been synthesized from the reaction of Ir(CH₃)I₂(CO) (dppe) and silver triflate. Methane and IrH(CO) (CF₃SO₃)₂ (dppe) (2) are formed when a methylene chloride solution of 1 is placed under 760 torr dihydrogen. Conductivity studies indicate that methylene chloride solutions of complexes 1 and 2 are weak electrolytes and only partially ionized at concentrations above 1 mM. Complex 2 is an effective hydrogenation catalyst for ethylene and 1-hexene while acetone hydrogenation is inhibited by the formation of [IrH₂(HOCH(CH₃)₂) (CO) (dppe)] (OTf) (3). Linear dimerization and polymerization of styrene occurs via a carbocationic mechanism initiated by triflic acid elimination from 2. Treatment of an acetonitrile solution of Ir(CH₃)I₂(CO) (dppe) with silver hexafluorophosphate produces the solvent promoted carbonyl insertion product [Ir(C(O)CH₃) (NCCH₃)₃ (dppe)] [PF₆]₂ (7) which readily undergoes deinsertion in methylene chloride to form [Ir(CH₃) (CO) (NCCH₃)₂ (dppe)] [PF₆]₂ (8) and acetonitrile.     

Slippage of η-allenyl/propargyl to an η structure and tautomerization of η-propargyl to η-allenyl in ligand addition and substitution reactions of platinum(II) complexes

Reactions of [(PPh₃)₂Pt(η³-CH₂CCPh)]OTf with each of PMe₃, CO and Br⁻ result in the addition of these species to the metal and a change in hapticity of the η³-CH₂CCPh to η¹-CH₂CCPh or η¹-C(Ph)=C=CH₂. Thus, PMe₃ affords [(PMe₃)₃Pt(η¹-C(Ph)=C=CH₂)]⁺, CO gives both [trans-(PPh₃)₂Pt(CO)(η¹-CH₂CCPh)]⁺ and [trans-(PPh₃)₂Pt(CO)(η¹-C(Ph)=C=CH₂)]⁺, and LiBr yields cis-(PPh₃)₂PtBr(η¹-CH₂CCPh), which undergoes isomerization to trans-(PPh₃)₂PtBr(η¹-CH₂CCPh). Substitution reactions of cis- and trans-(PPh₃)₂PtBr(η¹-CH₂CCPh) each lead to tautomerization of η¹-CH₂CCPh to η¹-C(Ph)=C=CH₂, with trans-(PPh₃)₂PtBr(η¹-CH₂CCPh) affording [(PMe₃)₃Pt(η¹-C(Ph)=C=CH₂)]⁺ at ambient temperature and the slower reacting cis isomer giving [trans-(PPh₃)(PMe₃)₂Pt(η¹-C(Ph)=C=CH₂)]⁺ at 54 °C . All new complexes were characterized by a combination of elemental analysis, FAB mas spectrometry and IR and NMR (¹H, ¹³C{¹H} and ³¹P{¹H}) spectroscopy. The structure of [(PMe₃)₃Pt(η¹-C(Ph)=C=CH₂)]BPh₄·0.5MeOH was determined by single-crystal X-ray diffraction analysis.