Axial CO Research Articles

Infrared characterization of alumina-supported Re 2(CO) 10 and Mn 2(CO) 10

The interaction of Re 2(CO) 10 and Mn 2(CO) 10 with highly dehydroxylated γ-A1 2O 3 is studied by means of a detailed examination of the IR spectra corresponding to increasing amounts of adsorbed metal carbonyl. Adsorption occurs via O-bonding between an axial CO ligand and Lewis acid centres present at the γ-Al 2O 3 surface. These are mainly bulk tetrahedral and bulk octahedral Al 3+ ions emerging on the surface. It is shown that the interaction between the adsorbed molecule and γ-Al 2O 3 is strong enough to cause a pronounced alteration of the IR spectrum of the metal carbonyl. Two sets of IR absorption bands are observed in the carbonyl stretching region. These are respectively assigned to M 2(CO) 10 (M = Mn, Re) interacting with two types of surface sites of different Lewis acid strengths.

ChemInform Abstract: Substitution Reactions of the Osmium(I) Dinuclear Compound (Os2(MeCO2)2(CO)6). X‐Ray Crystal Structure of (N(PPh3)2) (Os2(MeCO2)2Cl(CO)5).

AbstractThe dimer (I) has labile axial CO ligands and there is no evidence for equatorial substitution in its reactions.

ChemInform Abstract: Synthesis and Characterization of a New Family of Unsaturated Triangular Rhenium Cluster Anions of Formula (Re3(μ‐H)4(CO)9L)‐ (L: Neutral Two‐electron Donor Ligand). X‐Ray Crystal and Molecular Structures of the Tetraethylammonium Salts of the Anions with L: Triphenylphosphine and Pyridine.

AbstractThe unsaturated triangular cluster anion (I) can undergo selective substitution of one of the axial CO ligands of the Re(CO)4 vertex by neutral two‐electron donor ligands such as acetonitrile, triphenylphosphine, or pyridine giving the unsaturated derivatives (II).

Substitution reactions of the osmium(I) dinuclear compound [Os2(MeCO2)2(CO)6]. X-Ray crystal structure of [N(PPh3)2][Os2(MeCO2)2Cl(CO)5

The dinuclear osmium(I) compound [Os2(MeCO2)2(CO)6] has labile axial CO ligands and there is no evidence for equatorial substitution in its reactions. Refluxing tetrahydrofuran (thf) gives [Os2(MeCO2)2(CO)5(thf)] which reacts with tertiary phosphines to give [Os2(MeCO2)2(CO)5L](L = PPh3 or PMe2Ph) and with [N(PPh3)2]Cl to give [N(PPh3)2][Os2(MeCO2)2Cl(CO)5], the X-ray crystal structure of which confirms axial substitution. Direct reaction of [Os2(MeCO2)2(CO)6] with tertiary phosphines, pyridine, or acetonitrile ligands, L, gives the di-axially substituted compounds [Os2(MeCO2)2(CO)4L2] and no mono-substituted compounds were observed in most cases. Treatment of the 13CO-enriched compound [Os2(MeCO2)2(CO)6] with acetonitrile gives enriched [Os2(MeCO2)2(CO)4(MeCN)2]. This reacted with natural abundance CO to reform [Os2(MeCO2)2(CO)6] which contains 13CO only in sites cis to the Os–Os bond. Equilibration between these sites and those trans to the Os–Os bond is slow with t½=ca. 6 d at room temperature.

Self-injection of the CO 2 laser

A self-injection technique has been successfully applied to a low divergence, single axial mode TEA CO 2 laser. Pulse trains of ∼ 1.5 ns pulses have been observed with a power gain of a factor of ∼ 3 with respect to the natural configuration.

Laser enhancement of thermophoretic deposition processes

Axial CO 2 laser radiation has been shown to have a significant influence in modifying the deposition of silicon dioxide in the modified chemical vapor deposition (MCVD) fiber preform process. Experiments on soot deposition with a stationary burner have shown a doubling of both the rate of deposition and the deposition efficiency.

Molecular structures and dynamic behaviour of two isomers of [Ru3(µ-H)(µ3-Me2NC4H4)(CO)9] formed from 1-dimethylaminobut-2-yne and containing η2-alkene-1,3-diyl and η2-alkene-1,2-diyl ligands respectively

Single-crystal X-ray structures of the isomeric compounds [Ru3(µ-H)(µ3-MeCCCHNMe2)(CO)9](1) and [Ru3(µ-H)(µ3-MeCCHCNMe2)(CO)9](2), both prepared from [Ru3(CO)12] and the aminoalkyne MeCCCH2NMe2, have been determined. Isomer (1) formally contains the µ3-η2-alkyne MeCCCHN+ Me2 which requires the associated negative charge of the zwitterion to be located at the ruthenium atoms. 13C N.m.r. spectra reveal localised dynamic exchange of axial and equatorial CO ligands at Ru atoms and these processes together with a rotation of the µ3-alkyne lead to a single 13CO n.m.r. signal at +90 °C. The isomer (2) formed by heating (1), contains two 1,3-related Ru–C σ bonds and a η2-alkene group. Although there is localised axial–equatorial CO exchange at two of the three Ru atoms, no µ3 ligand rotation is observed in this case.

Synthesis and characterization of [Cr(CO)5{SCHCHC(SEt)2}] and [Cr(CO)5{SC(SCHCH2)SEt}] by ring-opening of 1,3-dithiolane-2-thione: crystal and molecular structure of [Cr(CO)5{SCHCHC(SEt)2}

The compound [Cr(CO)5{S[graphic omitted]}] reacted with Li(NPri2), CS2, and [Et3O][BF4] to afford either [Cr(CO)5{SCHCHC(SEt)2}](1) or [Cr(CO)5{SC(SCHCH2)SEt}](2) depending upon the reaction conditions employed. The crystal structure of the co-ordinated thioaldehyde (1) was determined [orthorhombic, space group Pbcm, a= 11.530(5), b= 18.745(9), c= 7.889(4)A, and Z= 4] and refined to R= 0.040 and R′= 0.038. All the atoms except those of four axial CO ligands and some hydrogens lie in one plane.

Molybdenum complexes of sterically hindered thiols. The preparation and structure of[Mo(CO)2(SC6H2Pri 3)3

The reaction of [MoCl4(thf)2](thf = tetrahydrofuran) with NaSC6H2Pri3 in thf under CO gives [Mo(CO)2(SC6H2 Pri3)3]–(1); an X-ray crystal structure shows a trigonal bipyramidal structure with axial CO groups.

Solvent effects on the infrared active CO stretching frequencies of some metal carbonyl complexes—I. Dimanganese decarbonyl and dirhenium decarbonyl

The infrared spectra of Mn 2(CO) 10 and Re 2(CO) 10 have been measured in the CO stretching region in the gas phase and in each of seventy four solvents and solvent shifts related to the parameter δ s . Using straight chained hydrocarbon solvents, there is a linear relationship between band frequency and δ s for all three ν(CO) modes for both compounds. While effects on b 2( b) and e 1 modes are similar for each compound a much larger effect occurs on the b 2( a) mode of Re 2(CO) 10 than that on the same mode of Mn 2(CO) 10. It is suggested that this is associated with greater double bond character in the axial CO groups reflected in the stronger ReRe bond for Re 2(CO) 10. Deviations that are both positive and negative are observed for all other solvents. Usually positive deviations occur with the highest frequency b 2( b) modes and negative deviations with the other modes. For polar solvents this has been explained in terms of the relative contribution of triple and double bond character to the CO groups involved and hence the sign of μ′ (the change in dipole moment with respect to the vibrational coordinate of the solute bond). As the alkyl chain is lengthened deviations become less positive (or more negative). This is explained from increase in + I effect of the alkyl group causing more polarity in the functional group which leads to a more negative value for μ′. Trends in solvent effect for branch chain hydrocarbons, alkenes and alkyl benzenes are also discussed.

Study of the CO stretching frequencies and intensities in metal-carbonyl compounds: Part III. The compounds {Co(CO)3L}2 with L an organophosphorus ligand

The force constants and dipole moment derivatives calculated for the title compounds show the same trends as those for the corresponding LFe(CO)4 and Hg{Co(CO)3L}2 compounds. From a comparative study of {Co(CO)3L}2 and Hg{Co(CO)3L}2 it is concluded that the Hg atom causes a depletion of electron density between the two Co(CO)3L moieties. Moreover, it acts as a buffer, weakening the effect of increased electron density on the Co atoms resulting from the substitution of ligands with stronger σ-donor and/or poorer π-acceptor properties for the axial CO groups.

Synthesis and structural characterization of the anion tri-μ-hydridoiodoundecacarbonyl-triangulo-trirhenate(1-)

The novel anion [Re 3H 3I(CO) 11] − has been obtained by reaction of ethanolic I 2 solutions with either [Re 4H 4I(CO) 15] − or [Re 4H 4(CO) 15] 2−. It has been characterized by IR, NMR and single-crystal X-ray analysis. The anion contains an equilateral metal atoms triangle (mean ReRe 3.265 Å) bearing six equatorrial and five axial CO groups. The iodide ligand is terminally bound in axial position (ReI 2.839(4) Å). The hydride ligands are bridging on the Re 3 triangular edges.

On the use of 13C 13C coupling in establishing intramolecular versus intermolecular CO ligand reaarangement processes in metal carbonyl derivatives

13C 13C spinspin coupling between axial and equatorial CO ligands in M(CO) 5L(M = Group VIB metal) derivatives is employed in establishing intramolecular versus intermolecular axialequatorial carbon monoxide ligand exchange pathways.

Syntheses and NMR studies of five-co-ordinate rhodium(I) complexes with α-diimines (RNC(H)C(H)NR): [RhCl(CO)(η 2-C 2H 4)(α-diimine)] and [RhCl(L) 2(α-diimine)] (R = t−Bu, EtMe 2C−; L = CO,PF 3)

Interaction of α-diimines (RNCHCHNR abbreviated as R-dim) with [LL′Rh(μ-Cl) 2RhLL′] (LL' CO or PF 3 and LCO, L′η 2-C 2H 4) gives rise to various equilibrium mixtures whose nature depends on L. [RhCl(CO)(η 2-C 2H 4)(R-dim)], which can be isolated, has according to 1H and 13C NMR spectra a five-co-ordinate structure. The σ,σ-N,N′ chelate R-dim and η 2-olefin ligands are in the trigonal plane of a trigonal bipyramidal array with the Cl and CO groupings residing in the axial positions, a geometry similar to that of recently reported [PtCl 2(η 2-styrene)(t-Bu-dim)]. The dynamic behaviour of [RhCl(CO)(η 2-C 2H 4)(R-dim)] which involves rotation of the ethylene around the Rhη 2-C 2H 4 axis, has been studied. These complexes readily lose ethylene providing four-co-ordinate [RhCl(CO)(R-dim)]. Five-co-ordinate [RhCl(CO) 2(R-dim)] obtained in solution are in equilibrium (slow on the NMR time scale) with free R-dim, the ionic [Rh(CO) 2(R-dim)][RhCl 2(CO) 2] and the dinuclear species [{RhCl(CO) 2} 2(R-dim)] of which the latter two are four-co-ordinate Rh I species. 1H and 13C NMR spectra point to a trigonal bipyramidal structure of the five-co-ordinate species in which the intramolecular exchange between the axial and equatorial CO groups is fast on the NMR time scale. According to 1H, 13C, 19F and 31P NMR spectra analogous [RhCl(PF 3) 2(R-dim) complexes have a trigonal bipyramidal structure with cis-PF 3 groups of which one PF 3 group occupies the axial position trans to Cl. The stability of the five- vs. the four-co-ordinate geometry of these RhR-dim complexes is discussed in terms of the branching at C α of R. A comparison is made with iso-electronic and iso-structural platinum(II)η 2-olefinR-dim complexes. The [RhCl(CO)(η 2-C 2H 4)(R-dim)] complexes readily undergo reversible R-dim exchange with 2,4,6-Me 3pyridine but afforded [RhCl(CO)(PPh 3) 2] irreversibly with PPh 3.

Vibrational spectrum of Ru3(CO)12; analogy with the adsorption system CO/Ru(001)

The A2″ vibrational mode of the axial CO ligands in Ru3(CO)12 is found to be identical in character and frequency to that of the collective C–O stretching mode in the adsorption system CO/Ru(001).

ChemInform Abstract: ORGANOMERCURY COMPLEXES OF IRON, COBALT, AND TUNGSTEN

AbstractDie Komplexe (I) wurden durch Reaktion von Fe(CO)5 mit Organoquecksilberchloriden in MeOH dargestellt.

Organomercury complexes of iron, cobalt, and tungsten

The iron complexes cis-[Fe(CO)4(HgR)2][R = CH2SiMe3, CH(SiMe3)2, or C(SiMe3)3] have been prepared. Their spectroscopic properties are reported, and their tendency to symmetrise, e.g. n[Fe(CO)4(HgR)2]→nHgR2+[{HgFe(CO)4}n], has been examined. The complex [Fe(CO)4{Hg[C(SiMe3)3]}2] resists thermal symmetrisation; it reacts with HgBr2 and with [Fe(CO)4(HgBr)2] forming HgBr[C(SiMe3)3] and [{HgFe(CO)4}n] probably via the intermediate [Fe(CO)4(HgBr){Hg[C(SiMe3)3]}]. At 60 °C the carbonyl groups in cis-[Fe(CO)4{Hg[C(SiMe3)3]}2] are fluxional, whereas at –55 °C axial and equatorial CO groups can be distinguished. The fluxional behaviour does not involve dissociation, and there is no evidence for the trans isomer. At 35 °C this complex shows an anomalous 13CO spectrum. The impure complexes [Co(CO)4(HgCH2SiMe3)] and [W(CO)3(η-C5H5)(HgCH2SiMe3)] are also reported.

Redox behaviour of group VIIB metal—metal bonded carbonyls: substitution effects

Electrochemical reduction parameters of M 2(CO) 10 (M 2 = Mn 2, MnRe, Re 2) (I) are compared with those of the related axially disubstituted M 2(CO) 8(PPh 3) 2 (II) compounds. With compounds II, the half-wave potentials are more cathodic than with compounds I. The same results are obtained from cyclic voltammetry on platinum electrode. From the electronic absorption spectra of compounds I and II, the energies of the σ → σ★ transitions associated with the metal—metal bond are calculated. In Mn 2(CO) 10 and MnRe(CO) 10 these energies correlate well with the electrochemical results: replacement of two axial CO groups by PPh 3 weakens the metal—metal bond. In contrast for Re 2(CO) 10 the same substitution reinforces the rhenium—rhenium bond.

Kristall- und molekülstruktur von tetracarbonyl-ferra-3-cyclopenten-2,5-dion

A single-crystal X-ray diffraction study of tetracarbonyl-ferra-3-cyclopentene-2,5-dione has been made. Formally the compound can be derived from maleic anhydride by substitution of the bridging oxygen by Fe(CO) 4. Accordingly the bonding character is similar to that of maleic anhydride. The ironcarbon distances in the ring indicate partial double bonds. The octahedrally coordinated iron atom is linked to four terminal carbon monoxide ligands, with a longer bond distance to the equatorial than to the axial ones (FeC ax 1.809 Å, FeC eq 1.854 Å). The axial CO groups are strongly inclined towards the ring (C axFeC ax 164°). The latter effect is explained by electronic repulsion of the CO groups. IR, 1H NMR, and 13C NMR data are reported. Crystal data: space group Pnama:α  12.708(10), b  10.058(7), c  7.527(5) Å; Z  4. With 625 reflections [F o > 3 o(F o)] the structure has been refined anisotropically (hydrogen isotropically) to R0.022.

乱流拡散火炎の特性について 燃料に都市ガスを用いた場合

As a combustion system in ships, turbulent diffusion flames are widely used. Yet such a combustion system involves various problems to be solved. One of them is that some ill effects are caused by the lowered quality of fuels, and another is how to burn such a fuel as is mixed with various noncombustible ingredients such as waste oil.We, therefore, in order to make basic explications about these problems above, made various experiments, using town gas as fuel, under the condition that overall equivalence ratio (φ) is less than the stoichiometric equivalence ratio.To sum up the results of our experiments, the most important points are as follows:(1) The temperature of the flame reaches its maximum value in the central regions 5cm-25cm from the nozzle tip, while it lowers as the distance from the nozzle tip becomes greater.(2) In regard to the gas analysing results of the axial distance, CO, H2 and unburnt hydrocarbon reach their peak value in the neighbourhood of the nozzle, but they become less in the rear-flow, and the combustion efficiency increases at the same time.(3) Because the overall equivalence ratio is made by changing the quantity of the combustion air, the diffusible width of flame is affected nice distinction to be entrainment of air transfer across the flame surface.It can be said that the experimental flames used in our experiments are not the pure diffusion flames, because we used town gas containing about 3.5 per cent oxygen.