Synthesis, molecular structure, substitution and C-C coupling reactions of ruthenium complexes containing (η-C9H7)Ru(PPh3) as a molecular unit

The 2-methallyl complex [(η⁵-C₉H₇)Ru(η³-2-MeC₃H₄)(PPh₃)] (3), prepared from [(η⁵-C₉H₇)Ru(PPh₃)₂Cl] (2) and 2-MeC₃H₄MgCl, reacts with HX (X = Cl, CF₃CO₂) in the presence of ethene to give the chiral-at-metal compounds [(η⁵-C₉H₇)Ru(C₂H₄)(PPh₃)X] (4, 5) in nearly quantitative yields. Treatment of 2 with AgPF₆ and ethene affords [(η⁵-C₉H₇)Ru(C₂H₄)(PPh₃)₂]PF₆ (6), which reacts with acetone to give the substitution product [(η⁵-C₉H₇)Ru(OCMe₂)(PPh₃)₂]PF₆ (7). The molecular structure of 7 has been determined crystallographically. Whereas treatment of 4 with CH(CO₂Et)N₂ yields the olefin complex [(η⁵-C₉H₇)Ru{η²-(Z)-C₂H₂(CO₂Et)₂}(PPh₃)Cl] (8), the reactions of 4 and 5 with Ph₂CN₂, PhCHN₂ and (Me₃Si)CHN₂ lead to the formation of the carbeneruthenium(II) derivatives [(η⁵-C₉H₇)Ru(CRR′)(PPh₃)Cl] (9-11) and [(η⁵-C₉H₇)Ru(CRR′)(PPh₃)(κ¹-O₂CCF₃)] (12-14), respectively. Treatment of 9 (R = R′ = Ph), 10 (R = H, R′ = Ph) and 11 (R = H, R′ = SiMe₃) with MeLi produces the hydrido(olefin) complexes [(η⁵-C₉H₇)RuH(η²-CH₂CPh₂)(PPh₃)] (15), [(η⁵-C₉H₇)RuH(η²-CH₂CHPh)(PPh₃)] (18a,b) and [(η⁵-C₉H₇)RuH(η²-CH₂CHSiMe₃)(PPh₃)] (19) via C-C coupling and β-hydride shift. The analogous reactions of 11 with PhLi gives the η³-benzyl compound [(η⁵-C₉H₇)Ru{η³-(Me₃Si)CHC₆H₅}(PPh₃)] (20). The η³-allyl complex [(η⁵-C₉H₇)Ru(η³-1-PhC₃H₄)(PPh₃)] (17) was prepared from 10 and CH₂CHMgBr by nucleophilic attack.     

Tetrameric 1:1 and monomeric 1:3 complexes of silver(I) halides with tri(p-tolyl)-phosphine: A structural and biological study

Silver(I) halides react with tri(p-tolyl)phosphine (tptp, C₂₁H₂₁P) in MeOH/MeCN solutions in 1:1 or 1:3 molar ratios to give complexes of formulae {[AgCl(tptp)]₄} (1) or [AgX(tptp)₃] (X = Cl (2), Br (3), I (4)), respectively. The complexes were characterized by elemental analyses, and FT-IR far-IR, FT-Raman, TG and ¹H, ¹³C, ³¹P NMR spectroscopic techniques. Crystal structures of complexes 2-4 were determined by X-ray diffraction at room temperature (rt). The crystal structure of 1 and 4 was also determined at 100(1) and 140(2) K (lt), respectively. In complex 1 four μ3-Cl ions are bonded with four Ag(I) ions forming a cubane while the coordination sphere of silver(I) ions is completed by one P atom from a terminal tri(p-tolyl)phosphine ligand. In complexes 2-3 one terminal halogen and three P atoms from phosphine ligands form a tetrahedral arrangement around the metal ion. Complexes 1-4 were tested for in vitro cytostatic activity against sarcoma cancer cells (mesenchymal tissue) from the Wistar rat, polycyclic aromatic hydrocarbons (PAH, benzo[a]pyrene) carcinogenesis and against murine leukemia (L1210) and human T-lymphocyte (Molt4/C8 and CEM) cells. The silver(I) complexes 1-4 show strong activity.     

Electrolyte effects on the intervalence transition within discrete binuclear cyano-bridged complexes. An estimation of activation free energy from static, optical and electrochemical data

A study of the metal-to-metal charge-transfer (MMCT) transition within the binuclear cyano-bridged complexes cis-[L¹³Co^III(μ-NC)Fe^II(CN)₅]⁻ (L¹³ = 12-methyl-1,4,7,10-tetraazacyclotridecan-12-amine), trans-[L¹⁴Co^III(μ-NC)Fe^II(CN)₅]⁻ (L¹⁴ = 6-methyl-1,4,8,11-tetraazacyclotetradecan-6-amine) and trans-[L¹⁵Co^III(μ-NC)Fe^II(CN)₅]⁻ (L¹⁵ = 10-methyl-1,4,8,12-tetraazacyclopentadecan-10-amine) has been carried out in electrolyte solutions at varying concentrations. Using these data, as well as the reaction free energies obtained from electrochemical measurements, the reorganisation and activation free energies for the forward and reverse thermal electron-transfer processes have been estimated. The changes of these parameters with the electrolyte concentration, as well as those of the energy of the maximum MMCT band and the reaction free energy, are mainly due to ion-pairing effects.     

Experimental evidence that flavonoid metal complexes may act as mimics of superoxide dismutase

Radical scavenging activities of flavonoids rutin, taxifolin, (-)-epicatechin, luteolin, and their complexes with transition metal (Fe2+, Fe3+, and Cu2+) towards superoxide were determined using illumination of riboflavin as source and NBT as detector of O*2-. The scavenger potencies of flavonoid metal complexes were significantly higher than those of the parent flavonoids. To elucidate the mechanism of this phenomenon, the rates of superoxide-dependent oxidation of flavonoids and their metal complexes in photochemical system with riboflavin were examined. It was found for the first time that flavonoids bound to metal ions were much less subjected to oxidation compared with those of free compounds. The findings directly demonstrate superoxide scavenging activity of metal ions in complexes with flavonoids and support earlier suggestions that flavonoid metal complexes may exhibit superoxide dismuting activity.     

Hierarchical Bayesian modeling of random and residual variance–covariance matrices in bivariate mixed effects models

Bivariate mixed effects models are often used to jointly infer upon covariance matrices for both random effects ( u ) and residuals ( e ) between two different phenotypes in order to investigate the architecture of their relationship. However, these (co)variances themselves may additionally depend upon covariates as well as additional sets of exchangeable random effects that facilitate borrowing of strength across a large number of clusters. We propose a hierarchical Bayesian extension of the classical bivariate mixed effects model by embedding additional levels of mixed effects modeling of reparameterizations of u‐ level and e ‐level (co)variances between two traits. These parameters are based upon a recently popularized square‐root‐free Cholesky decomposition and are readily interpretable, each conveniently facilitating a generalized linear model characterization. Using Markov Chain Monte Carlo methods, we validate our model based on a simulation study and apply it to a joint analysis of milk yield and calving interval phenotypes in Michigan dairy cows. This analysis indicates that the e ‐level relationship between the two traits is highly heterogeneous across herds and depends upon systematic herd management factors.     

Antibacterial activity and spectral studies of trivalent chromium,manganese, iron macrocyclic complexes derived from oxalyldihydrazide and glyoxal

A new series of complexes is synthesized by template condensation of oxalyldihydrazide and glyoxal in methanolic medium in the presence of trivalent chromium, manganese and iron salts forming complexes of the type: [M(C₈H₈N₈O₄)X]X₂ where M = Cr(III), Mn(III), Fe(III) and X = Cl^{? 1}, , CH₃COO^{? 1}. The complexes have been characterized with the help of elemental analyses, conductance measurements, magnetic susceptibility measurements, electronic, NMR, infrared and far infrared spectral studies. On the basis of these studies, a five coordinate square pyramidal geometry for these complexes has been proposed. The biological activities of the metal complexes were tested in vitro against a number of pathogenic bacteria and some of the complexes exhibited remarkable antibacterial activities.     

The use of the borocaptate anion as a ligand. Synthesis and X-ray crystal structure of pentaammine (1-thiolato-closo-undecahydrododecaborane)ruthenium(III) dihydrate

The complex [Ru(SB₁₂H₁₁)(NH₃)₅]·2H₂O has been prepared by the reaction of Cs₂B₁₂H₁₁SH with [RuCl(NH₃)₅]Cl₂ in aqueous solution. The complex represents the first reported example of the borocaptate anion acting as a ligand. The structure of the complex has been determined by single crystal X-ray diffraction analysis. The crystal parameters are monoclinic, space group P2₁/c, A = 8.056(1), B = 14.240(2), C = 15.172(2) Å, β=98.48° and Z = 4. The ruthenium atom has a distorted octahedral coordination. The distortion is probably due to the high (3⁻) charge and the large bulk of the borocaptate ligand. These features can also be observed in the spectroscopic properties of the complex.     

Further evidence from sectioned material in support of the existence of a linear terminal complex in cellulose synthesis

Summary Transmembrane linear terminal complexes considered to be involved in the synthesis of cellulose microfibrils have been described in the plasma membrane ofBoergesenia forbesii. Evidence for the existence of these structures has been obtained almost exlusively using the freeze etching technique. In the present study an attempt has been made to complete these studies using conventional fixation, staining, and sectioning procedures. In developing cells ofBoergesenia forbesii, strongly stained structures traversing the plasma membrane and averaging 598.9 nm ± 171.3 nm in length, 28.7 nm ± 4.2 nm in width, and 35.2 nm ± 6.6 nm in depth have been demonstrated. These structures are considered to be linear terminal complexes. At their distal (cell wall) surface, they appear to be closely associated with cellulose microfibrils. At the proximal (cytoplasmic) surface, they are associated with microtubules and polysomes. A model of the possible interrelation of the terminal complexes and microtubules leading to the generation of cell wall microfibrils is proposed.     

Identification of a cyanobacterial CRR6 protein,Slr1097, required for efficient assembly of NDH‐1 complexes in Synechocystis sp. PCC 6803

Despite significant progress in clarifying the subunit compositions and functions of the multiple NADPH dehydrogenase (NDH‐1) complexes in cyanobacteria, the subunit maturation and assembly of their NDH‐1 complexes are poorly understood. By transformation of wild‐type cells with a transposon‐tagged library, we isolated three mutants of Synechocystis sp. PCC 6803 defective in NDH‐1‐mediated cyclic electron transfer and unable to grow under high light conditions. All the mutants were tagged in the same slr1097 gene, encoding an unknown protein that shares significant homology with the Arabidopsis protein chlororespiratory reduction 6 (CRR6). The slr1097 product was localized in the cytoplasm and was required for efficient assembly of NDH‐1 complexes. Analysis of the interaction of Slr1097 with 18 subunits of NDH‐1 complexes using a yeast two‐hybrid system indicated a strong interaction with NdhI but not with other Ndh subunits. Absence of Slr1097 resulted in a significant decrease of NdhI in the cytoplasm, but not of other Ndh subunits including NdhH, NdhK and NdhM; the decrease was more evident in the cytoplasm than in the thylakoid membranes. In the ?slr1097 mutant, NdhH, NdhI, NdhK and NdhM were hardly detectable in the NDH‐1M complex, whereas almost half the wild‐type levels of these subunits were present in NDH‐1L complex; similar results were observed in the NdhI‐less mutant. These results suggest that Slr1097 is involved in the maturation of NdhI, and that assembly of the NDH‐1M complex is strongly dependent on this factor. Maturation of NdhI appears not to be crucial to assembly of the NDH‐1L complex.