Carbon-hydrogen Bond Cleavage Research Articles

PH and deuterium kinetic isotope effects studies on the oxidation of choline to betaine-aldehyde catalyzed by choline oxidase

The FAD-dependent choline oxidase catalyzes the four-electron oxidation of choline to glycine-betaine, with betaine-aldehyde as intermediate. The enzyme is capable of accepting either choline or betaine-aldehyde as a substrate, allowing the investigation of the reaction mechanism for both the conversion of choline to betaine-aldehyde and of betaine-aldehyde to glycine-betaine. In the present study, pH and deuterium kinetic isotope effects with [1,2- 2H 4]-choline were used to study the mechanism of oxidation of choline to betaine-aldehyde. The V/ K and V max pH-profiles increased to limiting values with increasing pH, suggesting the presence of a catalytic base essential for catalysis at the enzyme active site. From the V/ K pH-profile with [1,2- 2H 4]-choline, a p K a of 8.0 was determined for the catalytic base. This p K a was shifted to 7.5 in the V/ K pH-profile with choline, indicating a significant commitment to catalysis with this substrate. In agreement with this conclusion, the D( V/ K) values decreased from a limiting value of 12.4 below pH 6.5 to a limiting value of 4.1 above pH 9.5. The large D( V/ K) values at low pH are consistent with carbon–hydrogen bond cleavage of choline being nearly irreversible and fully rate-limiting at low pH. Based on comparison of amino acid sequences and previous structural and mechanistic studies on other members of the GMC oxidoreductase superfamily, the identity of the catalytic base of choline oxidase is proposed.

Bimetallo-radical carbon-hydrogen bond activation of methanol and methane.

Carbon-hydrogen bond cleavage reactions of CH3OH and CH4 by a dirhodium(II) diporphyrin complex with a m-xylyl tether (.Rh(m-xylyl)Rh.(1)) are reported. Kinetic-mechanistic studies show that the substrate reactions are bimolecular and occur through the use of two Rh(II) centers in the molecular unit of 1. Second-order rate constants (T = 296 K) for the reactions of 1 with methanol (k(CH3OH) = 1.45 x 10-2 M-1 s-1) and methane (k(CH4) = 0.105 M-1 s-1) show a clear kinetic preference for the methane activation process. The methanol and methane reactions with 1 have large kinetic isotope effects (k(CH3OH)/k(CD3OD) = 9.7 +/- 0.8, k(CH4)/k(CD4) = 10.8 +/- 1.0, T = 296 K), consistent with a rate-limiting step of C-H bond homolysis through a linear transition state. Activation parameters for reaction of 1 with methanol (DeltaH = 15.6 +/- 1.0 kcal mol-1; DeltaS = -14 +/- 5 cal K-1 mol-1) and methane (DeltaH = 9.8 +/- 0.5 kcal mol-1; DeltaS = -30 +/- 3 cal K-1 mol-1) are reported.

Bond activation by low valent ruthenium complexes

Ru(η4-1,5-cyclo-octadiene)(η6-1,3,5-cyclo-octatriene) (1) is one of the most versatile zero-valent ruthenium complexes bearing two labile cyclopolyenes and acts as a potential precursor for catalytic processes involving bond cleavage reactions in the presence of suitable Lewis bases. However, detailed studies of the bond cleavage step had, until now, been relatively less explored at a molecular level. The present Perspective is an account of our recent studies concerning: (1) the reactions of 1 with Lewis bases, (2) carbon–oxygen, carbon–sulfur, oxygen–hydrogen, nitrogen–hydrogen and carbon–hydrogen bond cleavage reactions by 1 in the presence of tertiary phosphine, (3) selective sp3 carbon–hydrogen bond cleavage by 1 by use of co-ordination of an anchoring chalcogen atom, and (4) preparation of an enolatoruthenium(II) complex derived from 1 as an active intermediate in chemoselective catalytic Knöevenagel and Michael reactions.

P450-mediated metabolism of 1-[3-(aminomethyl)phenyl]-N-[3-fluoro-2'-(methylsulfonyl)- [1,1'-biphenyl]-4-yl]-3-(trifluoromethyl)-1H-pyrazole- 5-carboxamide (DPC 423) and its analogues to aldoximes. Characterization of glutathione conjugates of postulated intermediates derived from aldoximes.

The in vivo and in vitro disposition of DPC 423, a highly potent, selective, and orally bioavailable inhibitor of blood coagulation factor Xa, has recently been described. Several metabolites, some of which were considered potentially reactive, were identified in rats. A novel GSH adduct, the structure of which was not determined conclusively, was isolated from bile of rats dosed with DPC 423. Herein, we describe the complete structural elucidation of this unique GSH conjugate employing LC/MS and high-field NMR. Similar GSH adducts of DPC 602, [13CD2]DPC 602, and SX 737, all structural analogues of DPC 423, were isolated, characterized spectroscopically, and shown to have identical mass fragmentation pathways. The structures of these conjugates were initially suspected to be either an amide with N-S bond or a nitrogen-oxygen juxtaposed amide with a C-S bond. Studies conducted with [13CD2]DPC 602 indicated an aldoxime structure. The concluding evidence came from HMBC NMR spectrum of the conjugate, which showed strong correlation of the cysteine methylene protons with the imino carbon. Further spectroscopic studies with chemically prepared GSH adduct from benzaldehyde oxime confirmed this pattern of correlation. In vivo and in vitro studies with the synthetic oxime intermediate from DPC 423 showed an adduct identical to the one isolated from the bile of rats dosed with DPC 423. This supported the intermediacy of an aldoxime as a precursor to the GSH adducts. It is postulated that the benzylamine moiety of DPC 423 (and its analogues) is oxidized to a hydroxylamine, which is subsequently converted to a nitroso intermediate. Subsequent rearrangement of the nitroso leads to an aldoxime which in turn is metabolized by P450 to a reactive intermediate. The formation of oxime from DPC 423 (and its analogues) was found to be mediated by rat CYP 3A1/2, which were also responsible for converting the oxime to the GSH trappable reactive intermediate. It is postulated that the aldoxime produces a radical or a nitrile oxide intermediate that reacts with GSH and hence produces this unusual GSH adduct. On the basis of synthetic analogy, it is more likely that the nitrile oxide resulting from two-electron oxidation of the aldoxime is the reactive intermediate. Intramolecular kinetic isotope effects were studied with [13CD2]DPC 602 to assess the importance of the metabolic cleavage of the aminomethyl carbon-hydrogen bond in forming this GSH adduct. The lack of isotope effect in forming the aldoxime from [13CD2]DPC 602 suggests its formation does not occur through the imine intermediate. Instead the data supports the postulated mechanism of hydroxylamine and nitroso intermediates as precursors to the aldoxime. However, the formation of the GSH adduct from [13CD2]DPC 602 did show a significant intramolecular kinetic isotope effect (kH/kD = 2.3) since a carbon-deuterium bond had to be broken on the aldoxime prior to the formation of the adduct. A stable nitrile oxide derived from DPC 602 was postulated as the reactive intermediate responsible for forming this unique GSH adduct.

Deuterium Isotope Effects during Carbon–Hydrogen Bond Cleavage by Trimethylamine Dehydrogenase: IMPLICATIONS FOR MECHANISM AND VIBRATIONALLY ASSISTED HYDROGEN TUNNELING IN WILD-TYPE AND MUTANT ENZYMES

His-172 and Tyr-169 are components of a triad in the active site of trimethylamine dehydrogenase (TMADH) comprising Asp-267, His-172, and Tyr-169. Stopped-flow kinetic studies with trimethylamine as substrate have indicated that mutation of His-172 to Gln reduces the limiting rate constant for flavin reduction approximately 10-fold (Basran, J., Sutcliffe, M. J., Hille, R., and Scrutton, N. S. (1999) Biochem. J. 341, 307-314). A kinetic isotope effect (KIE = k(H)/k(D)) accompanies flavin reduction by H172Q TMADH, the magnitude of which varies significantly with solution pH. With trimethylamine, flavin reduction by H172Q TMADH is controlled by a single macroscopic ionization (pK(a) = 6.8 +/- 0.1). This ionization is perturbed (pK(a) = 7.4 +/- 0.1) in reactions with perdeuterated trimethylamine and is responsible for the apparent variation in the KIE with solution pH. At pH 9.5, where the functional group controlling flavin reduction is fully ionized, the KIE is independent of temperature in the range 277-297 K, consistent with vibrationally assisted hydrogen tunneling during breakage of the substrate C-H bond. Y169F TMADH is approximately 4-fold more compromised than H172Q TMADH for hydrogen transfer, which occurs non-classically. Studies with Y169F TMADH suggest partial thermal excitation of substrate prior to hydrogen tunneling by a vibrationally assisted mechanism. Our studies illustrate the varied effects of compromising mutations on tunneling regimes in enzyme molecules.

Crossed beam reaction of phenyl radicals with unsaturated hydrocarbon molecules. I. Chemical dynamics of phenylmethylacetylene (C6H5CCCH3;X 1A′) formation from reaction of C6H5(X 2A1) with methylacetylene, CH3CCH(X 1A1)

The chemical reaction dynamics to form phenylmethylacetylene, C6H5CCCH3(X 1A′), via reactive collisions of the phenyl radical C6H5(X 2A1) with methylacetylene, CH3CCH(X 1A1), are unraveled under single collision conditions in a crossed molecular beam experiment at a collision energy of 140 kJ mol−1. The laboratory angular distribution and time-of-flight spectra of C9H8+ at m/e=116 indicate the existence of a phenyl radical versus hydrogen replacement pathway. Partially deuterated methylacetylene, CH3CCD(X 1A1), was used to identify the site of the carbon–hydrogen bond cleavage. Only the loss of the acetylenic hydrogen atom was observed; the methyl group is conserved in the reaction. Electronic structure calculations reveal that the reaction has an entrance barrier of about 17 kJ mol−1. Forward-convolution fitting of our data shows that the chemical reaction dynamics are on the boundary between an osculating complex and a direct reaction and are governed by an initial attack of the C6H5 radical to the π electron density of the C1 carbon atom of the methylacetylene molecule to form a short lived, highly rovibrationally excited (C6H5)HCCCH3 intermediate. The latter loses a hydrogen atom to form the phenylmethylacetylene molecule on the A′2 surface. The phenylallene isomer channel was not observed experimentally. The dynamics of the title reaction and the identification of the phenyl versus hydrogen exchange have a profound impact on combustion chemistry and chemical processes in outflows of carbon stars. For the first time, the reaction of phenyl radicals with acetylene and/or substituted acetylene is inferred experimentally as a feasible, possibly elementary reaction in the stepwise growth of polycyclic aromatic hydrocarbon precursor molecules and alkyl substituted species in high temperature environments such as photospheres of carbon stars and oxygen poor combustion systems.

Cryptoregiochemistry of the delta11-myristoyl-CoA desaturase involved in the biosynthesis of Spodoptera littoralis sex pheromone.

Many moth species biosynthesize their sex pheromones by the action of unique desaturases. These membrane-bound family of enzymes are especially interesting, since some of them produce (E)-unsaturated fatty acids either exclusively or along with the (Z)-isomer. In this article we present the first mechanistic study on one of these enzymes, namely, the Delta11-myristoyl-CoA desaturase of the moth Spodoptera littoralis. Intermolecular primary isotope effect determinations were performed in competition experiments. The unusual use of odd-number fatty acids, tridecanoic acid and deuterium-labeled tridecanoic acid, in these experiments showed the existence of a large isotope effect for the carbon-hydrogen bond cleavage at C11, but no isotope discrimination occurred in the removal of C12-H. The results of the competitive experiments are consistent with the hypothesis that this Delta11-desaturase involves a first slow, isotope-sensitive C11-H bond cleavage, with probable formation of an unstable intermediate, followed by a second fast C12-H bond removal. We suggest that a single enzyme may be responsible for the formation of both (Z)- and (E)-11-tetradecenoic acids by accommodating both gauche and anti conformers of the substrate, respectively. It is also possible that two mechanistically identical discrete enzymes are involved in each desaturation. In this case, the geometry of the resulting double bond would result from the different conformation adopted by the acyl substrate at each enzyme active site.

Preparation of 1,1,3,-Tetraisopropyl-l,3-Dichlorodisiloxane and Triisopropylchlorosilane

A facile, hydrochloric acid-free chlorination of silanes was developed. This allows for the elimination of siloxane bond cleavage and chlorination of carbon-hydrogen bonds during the chlorination of the Si-H bond.

A Novel Method. The Synthesis of Ketones and Azobenzenes Using Supported Permanganate

The heterogeneous use of potassium permanganate, sup- ported on copper(II) sulfate pentahydrate, provides a simple and ef- fective means for oxidizing amines. Primary aliphatic amines, such as sec-butylamine, are oxidized to the corresponding carbonyl com- pounds in good to excellent yields. Primary aromatic amines, such as 4-chloroaniline, are converted quantitatively into the correspond- ing azo compounds. Carbon-carbon bond cleavage, which usually occurs when alkylbenzene side chains are oxidized by perman- ganate under homogeneous conditions, does not occur. Under ap- propriate reaction conditions carbon-hydrogen bond cleavage at the benzylic position, known to occur under heterogeneous permanga- nate conditions, is also eliminated. For example, a quantitative yield of bis(2,4,6-trimethylphenyl)diazene is obtained from the oxidation of 2,4,6-trimethylaniline using small amounts of permanganate and copper(II) sulfate pentahydrate.

Mechanism based inactivation of the adenosylcobalamin-dependent ribonucleotide reductase from L. leichmannii by 2′-ara-2′-azido-2′-deoxy adenosine-5′-triphosphate: Observation of paramagnetic intermediates

Ribonucleotide reductases catalyze the reduction of nucleotides to deoxynucleotides in all organisms. 2′-Ara-2′-azido-2′-deoxyadenosin-5′-triphosphate (araN 3ATP) is a potent mechanism based inhibitor of the AdoCbl-dependent enzyme from Lactobacillus leichmannii (RTPR). Incubation of RTPR with [3′- 3H]- or [β- 32P]- or [8- 3H]-araN 3ATP reveals that inactivation is accompanied by covalent labeling, formation of cob(II)alamin and 5′-deoxyadenosine in a ratio of 0.4:0.4:0.4 equivalent/equivalent of RTPR. During this inactivation at least three paramagnetic species are detected by EPR spectroscopy. RTPR inactivation by araN 3ATP, in contrast to all other mechanism based inhibitors, does NOT appear to involve 3′-carbon-hydrogen bond cleavage.

Contrasting Values of Commitment Factors Measured from Viscosity, pH, and Kinetic Isotope Effects: Evidence for Slow Conformational Changes in theD-Amino Acid Oxidase Reaction

The flavoproteinD-amino acid oxidase catalyzes the oxidation ofD-amino acids to imino acids. Previous studies of pH and isotope effets on the reaction withD-alanine as substrate have established that the enzyme substrate complex partitions forward toward carbon–hydrogen bond cleavage 10 times as fast as the amino acid dissociates and that overall turnover is limited by product release. However, theV/Kvalue forD-alanine is not affected by the solution viscosity, while theVmaxvalue is only 15% limited by diffusion. These results are interpreted as evidence for a protein conformational change between an open conformation which binds substrates and a closed complex within which catalysis occurs. Such a model is supported by the recently reported structure of the enzyme–benzoate complex (A. Mattevi, M. A. Vanoni, F. Todone, M. Rizzi, A. Teplyakov, A. Coda, M. Bolognesi, and B. Curti (1996)Proc. Natl. Acad. Sci. USA93,7496–7501).

Chloranil-Sensitized Photolysis of Benzyltrimethylsilanes. Solvent Effect on the Competition between Carbon-Hydrogen and Carbon-Silicon Bond Cleavage

Chloranil-Sensitized Photolysis of Benzyltrimethylsilanes. Solvent Effect on the Competition between Carbon-Hydrogen and Carbon-Silicon Bond Cleavage

193 + 222 nm enhanced photolysis of selectively deuterated 2-chloropropane. A direct investigation of site-specific bond cleavage in the intermediate photofragment (s)

Selectively deuterated 2-chloropropane (CD 3CHClCD 3) is used to investigate photoinduced, site-specific CH (or CD) bond cleavage. In this study, a two-color photolysis approach is employed to create an intermediate photofragment(s) and then produce a neutral H or D atom from that photofragment(s). On a per site basis, the experimental results suggest that 222 nm photolysis of an intermediate, most likely the isopropyl radical, will preferentially induce carbon-hydrogen bond cleavage at the 2-position — not the lowest energy pathway.

Isotope effects on the cleavage of DNA by bleomycin: Mechanism and modulation

Sequence-specific isotope effects on the cleavage of DNA at thymidine residues by activated iron.bleomycin (Fe.BLM) have been observed upon incorporation of [4'-2H]thymidine into the DNA. The effects may be quantitated by end-labeling the DNA with phosphorus-32, generating a sequence ladder by gel electrophoresis, and measuring the relative damage at cleavage sites by autoradiography or phosphorimager technology. Results with DNA deuteriated at other positions of the deoxyribose ring, such as, the 5'- or 2'-carbon, afford no isotope effect suggesting high regiospecificity for the BLM-mediated carbon-hydrogen bond cleavage. The magnitude of the 4'-isotope effects for Fe.BLM ranges from 2 to 7 (+/- 0.3) and is not sensitive to changes in the partition ratio of the two proposed cleavage pathways. However, the isotope effect is sensitive to structural changes in BLM, such as with tallysomycin, and to changes in metal and cleavage mechanism, such as with Co.BLM. The variability of the effects are discussed in light of the factors responsible for the observation of V/K isotope effects. The findings suggest that the kinetics, thermodynamics, and geometry of carbon-hydrogen bond cleavage by Fe.BLM permit the observation of large isotope effects on this chemical step. Fe.BLM may be viewed, therefore, as a special case.

A model for the role of multiple cysteine residues involved in ribonucleotide reduction: amazing and still confusing.

Ribonucleotide reductase from Escherichia coli catalyzes the conversion of nucleotides to deoxynucleotides. Multiple cysteins have been postulated to play a key role in this process. To test the role of various cysteines in nucleotide reduction, a variety of single and double mutants of the R1 subunit were prepared: C754S, C759S, C754-759S, C462S, C462A, C230S, and C292S. Due to the expression system, each mutant contains small amounts of contaminating wt-R1 (estimated to be 1.5-3% based on activity). An epitope tagging method in conjunction with anion exchange chromatography was used to partially resolve the mutant R1 from the wt-R1. The interaction of these mutants with the normal substrate was studied, which allowed a model to be proposed in which five cysteines of the R1 subunit of RDPR play a role in catalysis. C754S and C759S R1s catalyze CDP formation at rates similar to wt-R1 when DTT is used as a reductant. However, when thioredoxin (TR)/thioredoxin reductase (TRR)/NADPH is used as reductant, the rates of dNDP production are similar to those expected for contaminating wt-R1 present as a heterodimer with the mutant. The impaired nature of these mutants with respect to reduction by TR suggests that their function is to transfer reducing equivalents from TR to the active site disulfide of R1 produced during NDP reduction. Single-turnover experiments, designed to avoid the problem of contaminating wt-R1, also support this role for C754 and C759. The double serine mutant of 754 and 759 has catalytic activity with DTT that is one-third the rate of wt-R1 with thioredoxin. C225 and C462 are thought to be the active site cysteines oxidized concomitantly with NDP reduction. Conversion of these cysteines to serines results in R1 mutants which convert the normal substrate into a mechanism-based inhibitor. C462SR1 upon incubation with R2 and [3'-3H,U-14C]UDP results in uracil release, 3H2O production, 3H,14C-labeled protein which has an absorbance change at 320 nm, and slow loss of the tyrosyl radical on R2. The isotope effect (kH/k3H) on 3' carbon-hydrogen bond cleavage is 1.7. This sequence of events is independent of the reductant, consistent with the postulate that C462 is an active site thiol. The C462AR1 has properties similar to C462SR1. Several additional mutant R1s, C230SR1, and C292SR1 were shown to have activities similar to wt-R1 with both TR/TRR/NADPH and DTT.

Interaction of C225SR1 mutant subunit of ribonucleotide reductase with R2 and nucleoside diphosphates: tales of a suicidal enzyme

Ribonucleotide reductase (RDPR) from Escherichia coli is composed of two subunits, R1 and R2, both of which are required to catalyze the conversion of nucleotides to deoxynucleotides. This reduction process is accompanied by oxidation of two cysteines within the active site to a disulfide. One of these putative active site cysteines, C225, has been mutated to a serine, and the properties of this mutant (C225SR1) have been investigated in detail. Incubation of C225SR1 and R2 with [3'-3H,U-14C]UDP results in time-dependent inactivation of the enzyme! This inactivation is accompanied by production of 2.4 uracils, 3H2O, and 3H,14C-labeled protein with an absorbance change at 320 nm. There is an isotope effect (kH/k3H) on uracil production of 3.2. In addition, the tyrosyl radical on R2 is reduced. The observation of 3H2O, indicative of 3' carbon-hydrogen bond cleavage and loss of the tyrosyl radical, provides a direct test of our mechanistic hypothesis that cleavage of this bond occurs concomitantly with tyrosyl radical reduction. Incubation of [3'-2H]UDP with C225SR1 and R2 resulted in a V and V/K isotope effect on loss of the radical of 2.0 and 2.0, respectively. These studies provide the first direct evidence for protein radical involvement in catalysis. Reduction of the tyrosyl radical on R2 is accompanied by a stoichiometric cleavage of the R1 polypeptide into two new polypeptides of 26 and 61 kDa. The 26-kDa polypeptide is the N-terminus of R1, and hence cleavage of the polypeptide is occurring in the region of the mutation. The N-terminus of the 61-kDa polypeptide is blocked.(ABSTRACT TRUNCATED AT 250 WORDS)

A model for homogeneous hydrodesulfurization. The importance of .eta.2-coordination and sulfur coordination in carbon-hydrogen and carbon-sulfur bond cleavage reactions of thiophene

A model for homogeneous hydrodesulfurization. The importance of .eta.2-coordination and sulfur coordination in carbon-hydrogen and carbon-sulfur bond cleavage reactions of thiophene

Conclusive evidence for site-specific C–H bond cleavage resulting from 248 nm photolysis of the ethyl radical

Experiments involving two photolysis lasers and one probe laser demonstrate that 248 nm excimer laser radiation will induce C–H bond cleavage preferentially at the β position in the ethyl radical. To facilitate carbon site labeling, selectively deuterated chloroethanes (ClCH2CD3 and ClCD2CH3) are used as precursor compounds. Two-photon ionization via resonance with the Lyman-α transition is used to detect H (or D) atoms. An initial 193 nm photolysis pulse serves to cleave the C–Cl bond in ClCH2CH3, while a second pulse at 248 nm dramatically enhances H-atom production. Experiments on ClCH2CD3 and ClCD2CH3 clearly show that this enhancement occurs preferentially through carbon–hydrogen bond cleavage at the β carbon site. It is apparent that 248 nm photon absorption by the ethyl radical is an important step in the overall mechanism.

Steady-state kinetic mechanism of rat tyrosine hydroxylase.

The steady-state kinetic mechanism for rat tyrosine hydroxylase has been determined by using recombinant enzyme expressed in insect tissue culture cells. Variation of any two of the three substrates, tyrosine, 6-methyltetrahydropterin, and oxygen, together at nonsaturating concentrations of the third gives a pattern of intersecting lines in a double-reciprocal plot. Varying tyrosine and oxygen together results in a rapid equilibrium pattern, while the other substrate pairs both fit a sequential mechanism. When tyrosine and 6-methyltetrahydropterin are varied at a fixed ratio at different oxygen concentrations, the intercept replot is linear and the slope replot is nonlinear with a zero intercept, consistent with rapid equilibrium binding of oxygen. All the replots when oxygen is varied in a fixed ratio with either tyrosine or 6-methyltetrahydropterin are nonlinear with finite intercepts. 6-Methyl-7,8-dihydropterin and norepinephrine are competitive inhibitors versus 6-methyltetrahydropterin and noncompetitive inhibitors versus tyrosine. 3-Iodotyrosine, a competitive inhibitor versus tyrosine, shows uncompetitive inhibition versus 6-methyltetrahydropterin. At high concentrations, tyrosine is a competitive inhibitor versus 6-methyltetrahydropterin. These results are consistent with an ordered kinetic mechanism with the order of binding being 6-methyltetrahydropterin, oxygen, and tyrosine and with formation of a dead-end enzyme-tyrosine complex. There is no significant primary kinetic isotope effect on the V/K values or on the Vmax value with [3,5-2H2]tyrosine as substrate. No burst of dihydroxyphenylalanine production is seen during the first turnover. These results rule out product release and carbon-hydrogen bond cleavage as rate-limiting steps.

Phase-transfer-catalyzed cleavage of carbon-hydrogen and carbon-phosphorus bonds in PPh3 by an iridium complex. Synthesis and molecular structure of [Ir2(C5Me5)2(.mu.-H)(.mu.-PPh2)(.mu.-C6H4)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhase-transfer-catalyzed cleavage of carbon-hydrogen and carbon-phosphorus bonds in PPh3 by an iridium complex. Synthesis and molecular structure of [Ir2(C5Me5)2(.mu.-H)(.mu.-PPh2)(.mu.-C6H4)]V. V. Grushin, A. B. Vymenits, A. I. Yanovskii, Yuri T. Struchkov, and M. E. Vol'pinCite this: Organometallics 1991, 10, 1, 48–49Publication Date (Print):January 1, 1991Publication History Published online1 May 2002Published inissue 1 January 1991https://doi.org/10.1021/om00047a025RIGHTS & PERMISSIONSArticle Views105Altmetric-Citations20LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (258 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts