Monocarbonyls

The first report of oxidative carbonylation is the reaction of alkenes with CO in benzene in the presence of PdCh to afford the /3-chloroacyl chloride 224[12,206]. The oxidative carbonylation of alkene in alcohol gives the q, f3-unsaturated ester 225 and /3-alkoxy ester 226 by monocarbonylation, and succinate 111 by dicarbonylation depending on the reaction conditions[207-209]. The scope of the reaction has been studied[210]. Succinate formation takes... 

Since the structures of the Gabriel-Isay condensation products of 5,6-diaminopyrimidines with unsymmetrical 1,2-dicarbonyl or a-substituted monocarbonyl compounds are always ambiguous, the synthesis of 6- and 7-substituted pteridines by an unambiguous approach was and still is a necessity and an important challenge. 

Polyfluoroaromatic Monocarbonyl Compounds (Russ) Gerasimova, T N, Fokin, E. P Vsp. Khun. 49, 1057-1078 148... 

RuCl2(PPh3)2 reacts with 4-R2P-dibenzothiophene (R = Ph, p-Tol) and forms 303, in which the dibenzothiophene ligand is coordinated to ruthenium via the phosphorus and sulfur atoms [84JA5379, 87JOM(318)409]. The donor ability of the sulfur atom is relatively weak. Complex 303 (R = Ph) is able to add carbon monoxide and yield the monocarbonyl adduct. 

Both the malonic ester synthesis and the acetoacetic ester synthesis are easy to cany out because they involve unusually acidic dicarbonyi compounds. As a result, relatively mild bases such as sodium ethoxide in ethanol as solvent can be used to prepare the necessary enolate ions. Alternatively, however, it s also possible in many cases to directly alkylate the a position of monocarbonyl compounds. A strong, stericaliy hindered base such as LDA is needed so that complete conversion to the enolate ion takes place rather than a nucleophilic addition, and a nonprotic solvent must be used. 

G If one of the carbonyl partners is much more acidic than the other and so is transformed into its enolate ion in preference to the other, then a mixed aldol reaction is likely to be successful. Ethyl acetoacetate, for instance, is completely converted into its enolate ion in preference to enolate ion formation from monocarbonyl partners. Thus, aldol condensations of monoketones with ethyl acetoacetate occur preferentially to give the mixed product. 

Carbon monoxide insertion reactions of CpFe(CO)LR are not common. The complex CpFe(CO)(PPh3)Me can be converted to the acetyl monocarbonyl with CO in refluxing petroleum ether ( 100°C) (227). By contrast, ultraviolet light-promoted reaction between CpFe(CO)(PPh3)R (R = Ph orp-CfiH4F) and CO yields CpFe(CO)2R (188). 

The band at 1994 cm observed at low CO coverage, was assigned to a monocarbonyl Rh(CO) species. The nature of the species observed at 2117cm has been elucidated using mixtures of different CO isotopes. As shown in Fig. 4, the band splits into three bands after adsorption of CO/ CO mixtures proving the presence of a dicarbonyl species... 

The intensity of the dicarbonyl at 2116cm is considerably reduced as compared to the 90 K deposit, indicating that the amount of metal atoms trapped at point defects is reduced for growth at 60 K. The difference in the nucleation sites is also reflected by the lower thermal stability of the systems, which decompose between 80 and 150 K as compared to 200 to 250 K for the 90 K deposits. With isotope mixing experiments the peak at 2087 cm was assigned to a carbonyl with three or more CO ligands, while the peak at 1999 cm is associated to a monocarbonyl [32]. 

It is remarkable that the feature at 2097 cm which was observed for a preparation at 90 K is missing at 60 K. The peak shows the characteristics of a monocarbonyl in mixing experiments. Furthermore, thermal treatment of the deposit as shown in Fig. 3a reveals a slightly increased thermal stability of this species as compared to the dicarbonyl at point defects. From this information it was suggested that the monocarbonyl is located at line defects of the alumina film [15]. 

Table Stoichiometry and corresponding IR stretching frequencies of different metal carbonyls. Charges for monocarbonyls were estimated from the correlation between IR stretching frequency and charge of the metal center as inferred from theoretical calculations (for details see [15,17]) ...

Schwerdtfeger, P. and Bowmaker, G.A. (1994) Relativistic effects in gold chemistry. V. Group 11 Dipole-Polarizabilities and Weak Bonding in Monocarbonyl Compounds. Journal of Chemical Physics, 100, 4487-4497. 

Fournier, R., 1993, Theoretical Study of the Monocarbonyls of First-Row Transition Metal Atoms , J. Chem. Phys., 99, 1801. 

Monocarbonyl 44 exhibited a doublet (2H-p = 3.5 Hz) at 84.59 in its 1H-NMR spectrum, assignable to the cyclopentadienyl protons coupled with the 31P nucleus. Its IR spectrum displayed a strong metal carbonyl band at 1932 cm-1, while the mass spectrum showed a parent ion at... 

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