1,3-二碘六氟丙烷的电子转移反应

在四醋酸铅的催化下,二氟二碘甲烷(CF2I2,1)与四氟乙烯加成生成1,3-二碘六氟丙烷(ICF2CF2CF2I,3).3与烯烃、炔烃和丙二酸二乙酯阴离子发生电子转移反应。     

Inter-channel effects in monosolvated atomic iodide cluster anion detachment: correlation of the anisotropy parameter with solvent dipole moment

Photoelectron imaging results are presented for I(-)[middle dot]X cluster anions (X = CO(2), C(4)H(5)N [pyrrole], (CH(3))(2)CO, CH(3)NO(2)). The available detachment channels are labeled according to the neutral iodine atom states produced (channel I ≡ (2)P(3/2) and channel II ≡ (2)P(1/2)). At photon energies in the vicinity of the channel II threshold these data are compared to previously reported results for I(-)[middle dot]X (X = CH(3)CN, CH(3)Cl, CH(3)Br, and H(2)O). In particular, these results show a strong connection between the dipole moment of the solvent molecule and the behavior of the channel I photoelectron angular distributions in this region, which is consistent with an electronic autodetachment process. The evolution of the channel II:channel I branching ratios in this excitation regime supports this contention.     

Reactions of a metallacyclobutene complex with alkenes

The first productive reactions of a characterized metallacyclobutene complex with alkenes are reported. Thus, the metallacyclobutene complex (eta5-C5H5)(PPh3)Co[kappa2-(C,C)-C(SO2Ph) C(Si(CH3)3)CH(CO2CH2CH3)] (2) undergoes reaction with alkenes to give 1,4-diene complexes with a high degree of regio- and stereoselectivity. A mechanism is proposed in which the metallacyclobutene generates a cyclic vinylcarbene intermediate that undergoes [4 + 2]-cycloaddition reactions with activated alkenes. A model of the vinylcarbene intermediate has been examined using quantum mechanical methods.     

Rearrangement of 3-membered 1,1,2-trifluorobromonium and iodonium ions and comparison of trifluorochloronium to fluorocarbenium ions

Reactions of chlorine (Cl(2)) with 4-halo-1,1,2-trifluorobut-1-enes (1, 2, or 3) give open-ion intermediates A and E that are in equilibrium. The open-chloronium ions (E) rearrange to a five-membered-ring halonium ion during ionic chlorination of 3 when the number-4 halo-substituent is iodine. Three-membered-ring bromonium and iodonium ions from alkenes 1, 2, or 3 are rather symmetrical and similar in structure. Quantum chemical calculations show that five-membered-ring halonium ion intermediates are 11 to 27 kcal/mol more stable than the three-membered-ring halonium ions or the open-ions A and E. The five-membered-ring intermediates lead to rearranged products. Rearranged products increase as the number-4 halogen (Z) becomes more nucleophilic (Z: Cl < Br < I). Open chloronium ions from ionic chlorination of terminal fluorovinyl alkenes are compared to the open ions generated by protons to similar alkenes.     

1,1'-(四甲基二硅撑)双[环戊二烯基三羰基钼配合物]的合成及结构

1,2-二环戊二烯基四甲基二硅烷与正丁基锂作用生成(四甲基二硅撑)双[环戊二烯基负离子盐],后者随即与六羰基钼反应即形成1,1'-(四 甲基二硅撑)双[环戊二烯基三羰基钼负离子盐],分别与四种不同的卤化物反应,生成在钼原子上发生烃基化的产物与冰醋酸作用,随即分别与CCl~4及NBS反应,生成相应的钼氯化物和钼溴化物作用发生氧化偶联反应,生成Mo-Mo键断裂的钼碘化物,以元素分析、IR及^1HNMR表征了2-9的结构.并对5的单晶进行了X射线衍射分析.它的晶体属三斜晶系,PI空间群,晶体学数据:偏差因子R=0.043,R~W=0.055.     

Photochemical and time resolved spectroscopic studies of intermediates relevant to iridium-catalyzed methanol carbonylation: photoinduced CO migratory insertion

Photoreaction, time-resolved infrared (TRIR), and DFT studies were utilized to probe transformations between iridium complexes with possible relevance to the mechanisms of the iridium/iodide-catalyzed methanol carbonylation to acetic acid. Solution-phase continuous and laser flash photolysis of the tetraphenylarsonium salt of the fac-[CH3Ir(CO)2I3]- anion (1a) under excess carbon monoxide resulted in migratory insertion to give the acyl complex ion mer,trans-[Ir(C(O)CH3)(CO)2I3]- (2a). The latter was isolated as its AsPh4+ salt, and its X-ray crystal structure was determined. TRIR spectra indicate that several transients are generated upon flash photolysis of 1a. The principal photoreaction is CO dissociation, and this is proposed to generate the isomeric complexes fac-[CH3Ir(CO)(Sol)I3]- (I(CO)(fac), Sol = solvent) and mer,trans-[CH3Ir(CO)(Sol)I3]- (I(CO)(mer)). I(CO)(fac) reacts with CO to regenerate 1a with a second-order rate constant (k(CO)) approximately 2.5 x 10(7) M(-1) s(-1) in ambient dichloroethane, while I(CO)(mer) is the apparent precursor to 2a. Kinetics studies indicate the photoinduced formation of a third intermediate (I(M)), hypothesized to be the anionic acyl complex fac-[Ir(C(O)CH3)(CO)(Sol)I3]-. In the absence of added CO, these intermediates undergo dimerization to form a mixture of isomers with the apparent formula [Ir(C(O)CH3)(CO)I3]2(2-). One of these dimers was isolated as the AsPh4+ salt, and the crystal structure was determined. Addition of excess pyridine to a solution of the dimers gave the neutral complex mer,trans-[Ir(C(O)CH3)(CO)(py)2I2], which was characterized by FTIR, NMR, and X-ray crystallography. These transformations, especially the unprecedented photoinduced CO insertion reaction, are discussed and interpreted in terms of the factors favoring migratory insertion dynamics.     

三(三甲硅基)环戊二烯基三羰基钼负离子的反应性

三(三甲硅基)环戊二烯基三羰基钼负离子锂盐[{η^5-(Me~3Si)~3C~5H~2}Mo(CO)~3]^-Li^+(1), 分别与MeI、phCH~2Cl及ClCH~2COOC~2H~5反应生成相应的烃基化钼衍生物[{η^5-(Me~3Si)~3C~5H~2}Mo(CO)~3R,] (R=-CH~3, 2; -CH~2ph, 3;-CH~2COOC~2H~5, 4)。1与PCl~3反应除得到预期的钼氯化物[{η^5-(Me~3Si)~3C~5H~2}Mo(CO)~3Cl](5)外, 主要得到钼磷氯化物[{η^5-(Me~3Si)~3C~5H~2}Mo(CO)~3PCl~2] 6; 1与碘反应得到钼碘化物[{η^5-(Me~3Si)~3C~5H~2}Mo(CO)~3I] 7; 1与HOAc作用后分别和CCl~4、NBS室温反应, 仅分离到脱去一个Me~3Si的钼卤化物[{η^5-(Me~3Si)~2C~5H~2}Mo(CO)~3X], (X:Cl, 8; Br, 9)。     

UV photodissociation of the van der Waals dimer (CH3I)2 revisited: pathways giving rise to ionic features

The CH(3)I A-state-assisted photofragmentation of the (CH(3)I)(2) van der Waals dimer at 248 nm and nearby wavelengths has been revisited experimentally using the time-of-flight mass spectrometry with supersonic and effusive molecular beams and the "velocity map imaging" technique. The processes underlying the appearance of two main (CH(3)I)(2) cluster-specific features in the mass spectra, namely, I(2)(+) and translationally "hot" I(+) ions, have been studied. Translationally hot I(+) ions with an average kinetic energy of 0.94+/-0.02 eV appear in the one-quantum photodissociation of vibrationally excited I(2)(+)((2)Pi(32,g)) ions (E(vib)=0.45+/-0.11 eV) via a "parallel" photodissociation process with an anisotropy parameter beta=1.55+/-0.03. Comparison of the images of I(+) arising from the photoexcitation of CH(3)I clusters versus those from neutral I(2) shows that "concerted" photodissociation of the ionized (CH(3)I)(2)(+) dimer appears to be the most likely mechanism for the formation of molecular iodine ion I(2)(+), instead of photoionization of neutral molecular iodine.     

Cobalt-catalyzed highly regio- and stereoselective intermolecular reductive coupling of alkynes with conjugated alkenes

In the presence of Co(PPh3)2I2, PPh3, water, and zinc powder, the reaction of alkynes (R1CCR2: R1 = Ph, R2 = Me (1a); R1 = Ph, R2 = Ph (1b); R1 = Et, R2 = Et (1c); R1 = Ph, R2 = (CH2)3OH (1d); R1 = CO2Et, R2 = Ph (1e); R1 = CO2Me, R2 = (CH2)4CH3 (1f); R1 = CO2Et, R2 = SiMe3 (1g)) with alkenes having an electron-withdrawing substituent (CH2=CHR: R = CO2Bu (2a), CN (2b), SO2Ph (2c) and CO2Me (2d)) proceeded smoothly in acetonitrile to give the corresponding reductive coupling products (R1HC=CR2CH2CH2R, 3a-j) in fair to excellent yields. This reductive coupling is highly regio- and stereoselective; only one isomer was observed for each reaction. The results of an isotope-labeling experiment using D2O (99%) to replace normal water for the reductive coupling of vinyl phenyl sulfone 2c with alkyne 1a revealed that the product is E-Ph(D)C=CMeCH2CH(D)SO2Ph deuterated at the olefinic proton and one of the protons of the alpha-methylene group in 84 and 96%, respectively. Possible mechanisms for this highly regio- and stereoselective ene-yne catalytic reaction are proposed.     

Activation of alkenes and H2 by [Fe]-H2ase model complexes

The established ability of the Fe(II) bridging hydride species (micro-H)(micro-pdt)[Fe(CO)2(PMe3)]2+, 1-H+, to take-up and heterolytically activate dihydrogen, resulting in H/D scrambling of H2/D2 and H2/D2O mixtures (Zhao et al. Inorg. Chem. 2002, 41, 3917) has prompted a study of simultaneous alkene/H2 activation by such [Fe]H2ase model complexes. That the required photolysis produced an open site was substantiated by substitution of CO in 1-H+ by CH3CN with formation of structurally characterized [(micro-H)(micro-pdt)[Fe(CO)2(PMe3)][Fe(CO)(CH3CN)(PMe3)]]+[PF6]-. Under similar photolytic conditions, H/D exchange reactions between D2 and terminal alkenes (ethylene, propene and 1-butene), but not bulkier alkenes such as 2-butene or cyclohexene, were catalyzed by 1-H+ and the edt (SCH2CH2S) analogue, 2-H+. Substantial regioselectivity for H/D exchange at the internal vinylic hydrogen was observed. The extent to which the olefins were deuterium enriched vs deuterated was catalyst dependent. The stabilizing effect of the binuclear chelating ligands, SCH2CH2CH2S, pdt, and SCH2CH2S, edt, is required for the activity of binuclear catalysts, as the mono-dentate micro-SEt analogue decomposed to inactive products under the photolytic conditions of the catalysis. Reactions of 1 and 2 with EtOSO2CF3 yielded the S-alkylated products, [(micro-SCH2CH2CH2SEt)[Fe(CO)2(PMe3)]2]+[SO3CF3]- (1-Et+), and 2-Et+, rather than micro-C2H5 analogues to the micro-H of 1-H+. The stability and lack of reactivity toward H2 of 1-Et+ and 2-Et+, indicates they are not on the reaction path of the olefin/D2 H/D exchange process. A mechanism with olefin binding to an open site created by CO loss and formation of an Fe-(CH2CHDR) intermediate is indicated. A likely role of a binuclear chelate effect is implicated for the unique S-XXX-S cofactor in the active site of [Fe]H2ase.     

Aerobic intramolecular aminothiocyanation of unactivated alkenes promoted by in situ generated iodine thiocyanate

Aerobic intramolecular aminothiocyanation of unactivated alkenes has been developed by in situ generated iodine thiocyanate under open-flask conditions. This protocol provides a concise and efficient method for synthesizing SCN-containing pyrrolidine, piperidine and indoline derivatives with isolated yields of up to 87%. Furthermore, mixing iodine and sodium thiocyanate with oxygen afforded iodine thiocyanate (ISCN) and dithiocyanatoiodate [I(SCN)₂]^- which were testified by liquid chromatography mass spectrometry. A mechanistic investigation indicates that iodonium ion and sulfonium ion intermediates might be involved in this transformation.     

Rhodium(I) and Rhodium(III) complexes containing the chiral ligand 2,6-bis[4'(S)-isopropyloxazolin-2'-yl]pyridine (pybox): an unprecedented monohapto coordination of pybox

The complex [Rh(kappa(3)-N,N,N-pybox)(CO)][PF(6)] (1) has been prepared by reaction of the precursor [Rh(mu-Cl)(eta(2)-C(2)H(4))(2)](2), 2,6-bis[4'(S)-isopropyloxazolin-2'-yl]pyridine (pybox), CO, and NaPF(6). Complex 1 reacts with monodentate phosphines to give the complexes [Rh(kappa(1)-N-pybox)(CO)(PR(3))(2)][PF(6)] (R(3) = MePh(2) (2), Me(2)Ph (3), (C(3)H(5))Ph(2) (4)), which show a previously unseen monodentate coordination of pybox. Complex 1 undergoes oxidative addition reactions with iodine and CH(3)I leading to the complexes [RhI(R)(kappa(3)-N,N,N-pybox)(CO)][PF(6)] (R = I (5); R = CH(3) (6)). Furthermore, a new allenyl Rh(III)-pybox complex of formula [Rh(CH=C=CH(2))Cl(2)(kappa(3)-N,N,N-pybox)] (7) has been synthesized by a one-pot reaction from [Rh(mu-Cl)(eta(2)-C(2)H(4))(2)](2), pybox, and an equimolar amount of propargyl chloride.     

铑催化合成气转化为乙醇反应中甲酰基中间体的化学捕获

本文采用化学捕获法对铑基催化剂上合成气转化反应中的甲酰基中间体进行了化学捕获,在CO+2D_2反应后,用CH_3I进行的化学捕获反应中生成了CH_3CHO、CH_3CDO两种形式的乙醛;补充的Ar吹扫实验显示DCO的甲基化反应对生成的CH_3CDO有重要贡献。因此,甲酰基的确是合成气反应中的C_1含氧中间体。根据这一结果,初步探讨了合成气反应中CH_x物种的生成途径。     

Gyroscope-like molecules consisting of three-spoke stators that enclose "switchable" neutral dipolar rhodium rotators; reversible cycling between faster and slower rotating Rh(CO)I and Rh(CO)2I species

trans-Rh(CO)(Cl)(P((CH(2))(14))(3)P) is prepared from trans-Rh(CO)(Cl)(P((CH(2))(6)CH[double bond, length as m-dash]CH(2))(3))(2) by a metathesis/hydrogenation sequence, and converted by substitution or addition reactions to Rh(CO)(I), Rh(CO)(2)(I), Rh(CO)(NCS), and Rh(CO)(Cl)(Br)(CCl(3)) species; the Rh(CO)(Cl) and Rh(CO)(I) moieties rapidly rotate within the cage-like diphosphine, but the other rhodium moieties do not.     

Influence of ion pairing on the oxidation of iodide by MLCT excited states

The oxidation of iodide to diiodide, I(2)˙(-), by the metal-to-ligand charge-transfer (MLCT) excited state of [Ru(deeb)(3)](2+), where deeb is 4,4'-(CO(2)CH(2)CH(3))(2)-2,2'-bipyridine, was quantified in acetonitrile and dichloromethane solution at room temperature. The redox and excited state properties of [Ru(deeb)(3)](2+) were similar in the two solvents; however, the mechanisms for excited state quenching by iodide were found to differ significantly. In acetonitrile, reaction of [Ru(deeb)(3)](2+*) and iodide was dynamic (lifetime quenching) with kinetics that followed the Stern-Volmer model (K(D) = 1.0 ± 0.01 × 10(5) M(-1), k(q) = 4.8 × 10(10) M(-1) s(-1)). Excited state reactivity was observed to be the result of reductive quenching that yielded the reduced ruthenium compound, [Ru(deeb(-))(deeb)(2)](+), and the iodine atom, I˙. In dichloromethane, excited state quenching was primarily static (photoluminescence amplitude quenching) and [Ru(deeb(-))(deeb)(2)](+) formed within 10 ns, consistent with the formation of ion pairs in the ground state that react rapidly upon visible light absorption. In both solvents the appearance of I(2)˙(-) could be time resolved. In acetonitrile, the rate constant for I(2)˙(-) growth, 2.2 ± 0.2 × 10(10) M(-1) s(-1), was found to be about a factor of two slower than the formation of [Ru(deeb(-))(deeb)(2)](+), indicating it was a secondary photoproduct. The delayed appearance of I(2)˙(-) was attributed to the reaction of iodine atoms with iodide. In dichloromethane, the growth of I(2)˙(-), 1.3 ± 0.4 × 10(10) M(-1) s(-1), was similar to that in acetonitrile, yet resulted from iodine atoms formed within the laser pulse. These results are discussed within the context of solar energy conversion by dye-sensitized solar cells and storage via chemical bond formation.     

Reduction of the allylic substituents in Ni(I)(1,8-dipropenyl-1,4,8,11-tetraazacyclotetradecane)+ by the central Ni(I) in aqueous solutions

The complex Ni(II)(1,8,-di-2-propenyl-1,4,8,11-tetraazacyclotetradecane)(2+), (NiL(1))(2+), was synthesized. X-ray crystallography demonstrates that the complex obtained is the trans-III isomer. The allylic substituents shift the redox couples (NiL(1))(3+/2+) and (NiL(1))(2+/+) anodically relative to the corresponding couples for Ni(II)(1,4,8,11-tetraazacyclotetradecane)(2+), (NiL(2))(2+), as expected. Surprisingly, the lifetime of (NiL(1))(+) in neutral aqueous solutions is shorter than that of (NiL(2))(+). Pulse radiolysis experiments reveal that the allylic substituents are reduced by the central Ni(I) ion. The first step in this reduction is a general acid catalyzed process. The results suggest that this step involves schematically the reaction Ni(I)[bond]NCH(2)CH[double bond]CH(2)(+) + H(+) --> Ni(III)[bond]NCH2CH2CH(2)(2+). The latter transient decomposes slowly with a half-life time of several minutes. Preliminary results support the suggestion that (NiL(2))(+), or other Ni(I)L complexes of this family, might reduce many alkenes present in the solution.     

Structure and unimolecular chemistry of protonated sulfur betaines, (CH3)2S(+)(CH2)(n)CO2H (n = 1 and 2)

The fixed charge zwitterionic sulfur betaines dimethylsulfonioacetate (DMSA) (CH(3))(2)S(+)CH(2)CO(2)(-) and dimethylsulfoniopropionate (DMSP) (CH(3))(2)S(+)(CH(2))(2)CO(2)(-) have been synthesized and the structures of their protonated salts (CH(3))(2)S(+)CH(2)CO(2)H···Cl(-) [DMSA.HCl] and (CH(3))(2)S(+)(CH(2))(2)CO(2)H···Pcr(-) [DMSP.HPcr] (where Pcr = picrate) have been characterized using X-ray crystallography. The unimolecular chemistry of the [M+H](+) of these betaines was studied using two techniques; collision-induced dissociation (CID) and electron-induced dissociation (EID) in a hybrid linear ion trap Fourier transform ion cyclotron resonance mass spectrometer. Results from the CID study show a richer series of fragmentation reactions for the shorter chain betaine and contrasting main fragmentation pathways. Thus while (CH(3))(2)S(+)(CH(2))(2)CO(2)H fragments via a neighbouring group reaction to generate (CH(3))(2)S(+)H and the neutral lactone as the most abundant fragmentation channel, (CH(3))(2)S(+)CH(2)CO(2)H fragments via a 1,2 elimination reaction to generate CH(3)S(+)=CH(2) as the most abundant fragment ion. To gain insights into these fragmentation reactions, DFT calculations were carried out at the B3LYP/6-311++G(2d,p) level of theory. For (CH(3))(2)S(+)CH(2)CO(2)H, the lowest energy pathway yields CH(3)S(+)=CH(2)via a six-membered transition state. The two fragment ions observed in CID of (CH(3))(2)S(+)(CH(2))(2)CO(2)H are shown to share the same transition state and ion-molecule complex forming either (CH(3))(2)S(+)H or (CH(2))(2)CO(2)H(+). Finally, EID shows a rich and relatively similar fragmentation channels for both protonated betaines, with radical cleavages being observed, including loss of ˙CH(3).     

Direct observation of reductive elimination of methyl iodide from a rhodium(III) pincer complex: the importance of sterics

A rare case of directly observed alkyl halide reductive elimination from rhodium is reported. Treatment of the naphthyl-based PCP-type Rh(III) methyl complexes 2a,b [(C10H5(CH2PR2)2)Rh(CH3)(I)] (R = iPr 2a, R = tBu 2b) with CO resulted in facile reductive elimination of methyl iodide in the case of 2b, yielding the Rh(I) carbonyl complex [(C10H5(CH2PR2)2)Rh(CO)] 3b (R = tBu), while the less bulky 2a formed CO adducts and did not undergo reductive elimination, contrary to expectations based on electron density considerations. Moreover, 3b oxidatively added methyl iodide, while 3a did not. CD3I/CH3I exchange studies in the absence of CO indicate that reversible formation of (ligated) methyl iodide takes place in both systems. Subsequently, when CO is present, it displaces methyl iodide in the bulkier tBu system, whereas with the iPr system formation of the Rh(III) CO adducts is favored. Iodide dissociation followed by its attack on the rhodium-methyl group is unlikely.     

Analysis of iodine species in aqueous solutions

Iodine is a biologically important trace element. Its behaviour in the environment and in human metabolism is determined by the type of iodine species which takes part in chemical reactions. Knowledge of their concentrations is necessary to understand and describe the iodine reaction paths. A separation procedure is proposed for quick determination of common forms of iodine-iodide, iodate ions, molecular iodine and organoiodine (in the form of CH(3)I). The procedure consists of sequential sorption by passing the sample solution first through a solid-phase extraction cartridge to separate I(2) and CH(3)I from IO(3)(-) and I(-) then through an anion-exchange resin in a cartridge to retain the latter two species. Each loaded cartridge is eluted to separate the sorbed pair of species. Concentration determination of the resulting four solutions can be performed by standard methods, e.g. by spectrophotometry, tracer counting or with ion-selective electrodes.     

Investigations by (13)C NMR spectroscopy of ethene-initiated catalytic CO hydrogenation

13C NMR spectroscopy shows that the n-alkene and n-alkane products from the catalytic hydrogenation of CO in the presence of (13)C(2)H(4) probes over Ru/150 degrees C, Co/180 degrees C, Fe/220 degrees C, or Rh/190 degrees C (1 atm, CO:H(2) 1:1, "mild conditions") contain terminal (13)CH(3)(13)CH(2)- units. This is consistent with their formation by a regiospecific polymerization of C(1) species derived from CO and initiated by (13)C(2)H(4). Although the activities toward individual products differed somewhat, similar distributions and similar product labeling patterns were obtained over all the four catalysts. 1-Butene and the higher 1-n-alkenes from all the catalysts were largely (13)CH(3)(13)CH(2)(CH(2))(n)()CH=CH(2) (n = 0-3), propene formed over Ru or Co was (13)CH(3)(13)CH=CH(2), while both (13)CH(3)(13)CH=CH(2) and (13)CH(2)=(13)CHCH(3) were formed over Fe or Rh. Comparison of the conclusions from these probe experiments with those from isotope transient experiments by other workers indicates that the ethene initiator does not significantly modify the course of the CO hydrogenation. The reaction products are largely kinetically determined, and the primary products are mainly linear 1-n-alkenes, while the n-alkanes and 2-n-alkenes largely arise via secondary processes. Since the distribution of products and the labeling in them is so similar, it is concluded that one basic primary mechanism applies over all the four metals. Several different reaction paths involving a polymerization of surface methylene, [CH(2(ad))], have been proposed. Although the predictions based on several of these mechanisms agree with many of the results, the alkenyl + [CH(2(ad))] mechanism, initiated by a surface vinyl [CH(2)=CH((ad))], most easily accommodates the experimental evidence. An alternative path involving sequential addition of surface methylidyne and hydride either to a growing alkylidene chain (alkylidene + [CH(ad) + H(ad)]) or to an alkyl chain (alkyl + [CH((ad)) + H(ad)]) has recently been proposed by van Santen and Ciobica. The [CH(2(ad))] mechanism offers an easier explanation for the formation of the various alkenes, the distribution of products, and of the initiation, while the [CH(ad) + H(ad)] mechanism can explain any n-alkanes formed as primary products and not derived from alkenes. At higher reaction temperatures over Ru and Co, considerable (13)C(1) incorporation (from natural abundance in the CO and from cleavage of the (13)C(2)H(4) probe) was found in all the hydrocarbons. Thus, at higher temperatures (13)C(1(ad)) in addition to (13)C(2(ad)) species participate in both chain growth and initiation. In summary, adsorbed CO is transformed very easily into surface C(1(ad)), probably [CH(2(ad))] in equilibrium with [CH((ad))+H(ad)], which act as the propagating species.