Carbon monoxide linear-bond

The adsorption of carbon monoxide on supported ruthenium has been extensively studied by IR spectroscopy (ref. 4). General agreement exists on the presence of three IR bands. The LF band at 1990-2030 cm" is assigned to the vibration of carbon monoxide linearly bonded on ruthenium crystallites. The bands at 2080 and 2140 cm correspond to the vibrations of a multicarbonyl. In a recent investigation (ref. 5) this species was shown to be a tricarbonyl associated with Ru cations bonded directly to the support. 

Thiirane 1,1-dioxides extrude sulfur dioxide readily (70S393) at temperatures usually in the range 50-100 °C, although some, such as c/s-2,3-diphenylthiirane 1,1-dioxide or 2-p-nitrophenylthiirane 1,1-dioxide, lose sulfur dioxide at room temperature. The extrusion is usually stereospeciflc (Scheme 10) and a concerted, non-linear chelotropic expulsion of sulfur dioxide or a singlet diradical mechanism in which loss of sulfur dioxide occurs faster than bond rotation may be involved. The latter mechanism is likely for episulfones with substituents which can stabilize the intermediate diradical. The Ramberg-Backlund reaction (B-77MI50600) in which a-halosulfones are converted to alkenes in the presence of base, involves formation of an episulfone from which sulfur dioxide is removed either thermally or by base (Scheme 11). A similar conversion of a,a -dihalosulfones to alkenes is effected by triphenylphosphine. Thermolysis of a-thiolactone (5) results in loss of carbon monoxide rather than sulfur (Scheme 12). 

An interesting carbene, 1-oxobutatrienylidene [25], having cumulated double bonds, has been found by IR spectroscopy in the photolysis (A>230nm) products of matrix-isolated l,2,3,4-pentatetraene-l,5-dione [26] (Maier et al., 1988) (in its turn the unstable dione [26] was generated by thermo- or photo-destruction of compound [27]). The second product was carbon monoxide. The linear structure of the carbene [25] has been suggested on the basis of two intense IR bands at 2222 cm and 1923 cm indicating respectively ketene and allene fragments. 

For small-molecule, metal-carbon monoxide complexes, the carbon monoxide ligand is almost always in a linear conformation and perpendicular to the metal. If one assumed bonding of CO to Hb or Mb in its normal linear, perpendicular mode, steric conflicts as illustrated in Figure 4.20 would occur and thus one might predict... 

The hydroformylation of olefins discovered by Otto Roelen [ 151 ] is one of the most important industrial homogeneously catalyzed reactions [152,153] for the synthesis of aldehydes with an estimated production of more than 9.2 million t in 1998 [ 153]. Hydroformylation is the addition of hydrogen and carbon monoxide to a C,C double bond. Industrial processes are based on cobalt or rhodiiun catalysts according to Eq. 1. The desired products are linear (n-) and branched (i-) aldehydes, in which the hnear products are generally favored for subsequent processing. 

Acetylium tetrafluoroborate was prepared in this way as early as 194324. and the structures of at least two acyl cations have been investigated by X-ray diffraction methods25-27. As expected, CH ,-C=0+ is linear about the central carbon, with a CO bond length of 1.12 A, just shorter than in carbon monoxide, and a very short C-C bond length of 1.38 A25 26. Structurally, therefore, the acyl cations closely resemble the isoelectronic nitriles. 

Carbon dioxide is a linear molecule with equivalent C O distances of 1.16 A (Vol pin and Kolomnikov, 1973). The bond strength in C02 is measured to be D= 127.1 kcal mol 1, relatively weak compared with the CO bond in carbon monoxide (D = 258.2 kcal mol ) (Bard et al., 1985 Latimer, 1952 Weast, 1978). Resonance structures of the C02 molecule as illustrated in Figure 3.2 show that its chemical reactivity is associated either with the presence of carbon oxygen double bonds and lone-paired electrons on the oxygen atoms or with the electrophilic carbon atom. The quantitative mole-... 

Hydroformylation is a precious metal-catalyzed reaction of synthesis gas, a 1 1 mixture of hydrogen and carbon monoxide, and an olefinic organic compound to form aldehydes. The reaction was discovered by Otto Roelen in 1938 in experiments for the Fischer-Tropsch reaction [8]. In Scheme 3, hydroformylation of a terminal olefin is shown in which the addition of carbon monoxide can be conducted at both carbon atoms of the double bond, thus yielding linear (n) and branched (iso) aldehydes. 

Ruthenium complexes are also suitable catalysts for carbonylation reactions of a variety of substrates. Indeed, when a reaction leads to C-Ru or het-eroatom-Ru bond formation in the presence of carbon monoxide, CO insertion can take place at the coordinatively unsaturated ruthenium center, leading to linear ketones or lactones. Thus, ruthenium-catalyzed carbonylative cyclization was involved in the synthesis of cyclopentenones by reaction of allylic carbonates with alkenes in the presence of carbon monoxide [124] (Eq. 93). 

Watanabe et al. [78] reported that the addition of C-H bonds in aldehydes to olefins took place efficiently with the aid of Ru3(CO)12 under a CO atmosphere at 200 °C (Eq. 50). In the case of the reaction with 1-hexene, a mixture of linear and branched ketones was obtained in 35% and 12% yields, respectively. To accomplish this reaction in a catalytic manner, the presence of carbon monoxide appears to be essential for suppressing the decarbonylation of aldehydes and for stabilizing the active catalyst species on the basis of the following observations ... 

A simple view of the mode of bonding of the carbon monoxide molecule to the surfaces of the transition metals and in their carbonyl complexes is well known and is thoroughly described in the literature.4 These metals have unfilled d-orbitals (or holes in their d-band), and the molecule in the linear form is held by a push-pull bond in which charge is transferred from the 5a orbital of the molecule into the metal s d-band, while there is back-donation of charge from the top of the d-band into the molecule s vacant... 

The nitric oxide molecule shows many similarities to carbon monoxide in its ability to form complexes with transition metals. Nitric oxide has an extra electron, occupying a n antibonding orbital, which is relatively easily lost. In the case of terminally bound NO, simple MO theory predicts that whilst M—NO+ will be linear, M—NO- may be a bent bond. The potential thus... 

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