Carbonyl complexes infrared spectra

Carbonyl complexes infrared spectra oxidative additions reactions structures syntheses... 

A second reason why AI is of value to scientists is that it offers powerful tools to cope with complexity. In favorable circumstances, the solutions to problems can be expressed by rules or by a well-defined, possibly trivial, model. If we want to know whether a compound contains a carbonyl group, we could record its infrared spectrum and check for a peak near 1760 cm1. The spectrum, paired with the rule that ketones generally show an absorption in this region, is all that we need. But other correlations are more difficult to express by rules or parametrically. What makes a good wine We may (or may not) be able to recognize a superior wine by its taste, but would have considerable difficulty in determining whether a wine is good, or even if it is palatable, if all we had to go on was a list of the chemicals of which it is comprised. 

G.A. Ozin, University of Toronto In our Cr/CO matrix cocondensation experiments (Angew. Chem., Int. Ed. Eng. 1975, 14, 292), we reported evidence for the facile formation of a binuclear chromium carbonyl complex Cr2(CO)i0 or Cr2 (CCOi x which could be described as square pyramidal Cr(CO)5 weakly interacting with either a Cr(CO)5 or Cr(CO)6 moiety in the vacant (sixth) site. As a result, the infrared spectrum of this "weakly-coupled" binuclear species closely resembled that of the mononuclear fragment Cr(CO)5. I would like to ask you, whether or not you have any evidence for the existence of such a binuclear species in your Cr(CO)6 /Xe cryogenic solutions following various photolysis treatments. 

Although this spectrum does not correspond to any particular ruthenium carbonyl complex, it is consistent with the presence of one or more anionic ruthenium carbonyl complexes, perhaps along with neutral species. Work is in progress with a variable path-length, high pressure infrared cell designed by Prof. A. King, to provide better characterization of species actually present under reaction conditions. 

The mixed-metal tetranuclear derivatives that have been prepared are H2Re2Ru2(CO)i6, CReRu3(CO)16] , HMnOs3(CO)16, and HReOs3(CO)18 (238). All the complexes result from the reaction of the carbonyl, M3(CO)i2, with the related anion, [Mn(CO)5]- or [Re(CO)s]. The ruthenium anion [ReRu3(CO)16] was isolated as its tetramethylammo-nium salt. The infrared spectrum was complex, but consistent with... 

The redox condensation shown in Eq. (9) gives rise to the dianion [Fe3Ni(CO)12]2 and it has also been possible to isolate salts of the corresponding hydride, [Fe3Ni(CO)12H]- (30.5 r). The presence of infrared absorptions due to bridging carbonyls and the complexity of the infrared spectrum indicate a structure similar to Co4(CO)i2 with the nickel in the basal plane171). 

The infrared spectrum in the carbonyl stretching region is very useful in characterizing these complexes (Table I). Three infrared active bands are predicted 18 however, limited solubility may preclude observation of the weaker bands. Dimer formation is easily detected by the presence of characteristic bands.12... 

Pentacarbonyl(diphenylmethylene)tungsten(0) is a moderately air-stable soild that is readily soluble in most organic solvents. The resulting solutions are air and light sensitive and decomposed thermally at about 50°. The infrared spectrum of a heptane solution shows bands in the metal carbonyl region at 2070 (m), 1971 (s), and 1963 (s) cm"1, characteristic of a group VI pentacar-bonyl species. The proton NMR spectrum in CS2 or acetone-d6 shows a complex multiplet at 5 7.2 relative to internal tetramethylsilane. 

The intermediate cyclooctene complex appears to be more reactive with respect to CS coordination and more sensitive to oxidation when the arene ring bears electron-withdrawing groups (e.g., C02CH3). Dicarbonyl(methyl rj6-benzoate)-thiocarbonyl)chromium is air stable in the solid state and reasonably stable in solution.9 The infrared spectrum exhibits metal carbonyl absorptions at 1980 and 1935 cm"1 and a metal thiocarbonyl stretch at 1215 cm"1 (Nujol) (these occur at 1978, 1932, and 1912 cm"1 in CH2C12 solution).10 Irradiation of the compound in the presence of phosphite or phosphine leads to slow substitution of CO by these ligands, whereas the CS ligand remains inert to substitution. The crystal structure has been published."... 

Cyclo-octatetraene reacts with iron carbonyls to form complexes with the compositions [Fe(CO)3(C8H8)], [Fe2(CO)6(C8H8)], and [Fe2(CO)7(C8H8)] 152, 168, 180). Nakamura and Hagihara 166) report that the complex [Fe(CO)3(C8H8)] decolorizes bromine in carbon tetrachloride and shows absorption bands in its infrared spectrum at 699, 716, and 720 cm-1 due to cis-double bonds. They suggest structure (XVI) for this complex, i.e., the hydrocarbon retains its tub form in the complex. These results are con-... 

The second binuclear complex [Fe2(CO)7(C8H8)] is a black solid, and appears to be a derivative of Fe2(CO)9, as it shows bands due to bridging carbonyl groups in its infrared spectrum (152). 

Treatment of complexes of the type [Co2(CO)6(RC CH)] with hydrochloric acid in ethanol gives stable complexes of the composition [C03-(CO)9(C2HR)H] 156). The acetylene complex (R = H) is neutral, soluble in organic solvents, diamagnetic, and the infrared spectrum shows the absence of bridging carbonyl groups. This acetylenic complex is identical with the product obtained by treating 1,1,1-trichloroethane with dicobalt... 

Isoelectronic with nickel carbonyl are the anions, Ni(CN)44- and Pd(CN)44-, which are obtained as their potassium salts by reduction of the corresponding cyanides of oxidation state +2 with potassium in liquid ammonia (32, 65, 186). The infrared spectrum of the nickel complex has been reported (67) to show only one band at 1985 cm-1, in the triple-bond... 

Physical properties depend upon the same types of steric effects as chemical reactivities. In both types of data the measurable phenomenon is occurring at a clearly defined active site. Thus, for the ionization of a set of phenols the active site is the OH group, while for the stretching frequency in the infrared spectrum of the acetyl group in a set of acetophenones the active site is the carbonyl group. In the case of bioactivities, steric effects in the formation of the bioactive substance-receptor site complex are frequently of great importance. In this case the entire bioactive... 

Interaction of C02 with petroleum ether solutions of cis-Mo(N2)2 (PMe3)4 results in the formation of the pale yellow complex trans-Mo (C03) (PMe3)4 and of variable amounts of the carbonyl-carbonate derivatives Mo(C03) CO(PMe3)4 and Mo(C03) CO(PMe3)3 2. The yellow complex is a micro-crystalline, moderately air stable solid, which can be heated at 40-50°C for several hours without noticeable decomposition. Its infrared spectrum displays bands at 1670, 1155 and 1100 cnr1, which by comparison with the spectrum of a sample 50% enriched in C02 can be assigned to vibrations associated with the coordinated C02 molecules, but no conclusions as to the coordination mode of the C02 ligand can be inferred from this data. 

---