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[en] It is shown that catalytic carbonylation of various compounds using iron carbonyl complexes is based on two types of reactions [redox disproportionation of iron carbonyl induced by Lewis bases and oxidative addition of Broensted and Lewis acids to (hydrido)carbonylferrate anions] comprising single-electron initiation steps and subsequent radical chain reactions. The role of iron carbonyl radical anions as catalysts for carbonylation processes with controlled reduction potential of the medium is noted. Characteristic features of the radical chemistry of iron and other transition metal carbonyls is analysed.
[en] Carbonylation of ethylene on cobalt catalysts in the presence of promoters was studied. It was shown that aromatic nitrogenous bases improve the stability of the catalytic system based on cobalt dioctacarbonyl and enable the carbonylation of ethylene in propanol-1 under substantially milder conditions, compared with the absence of a promoter. The carbonylation of ethylene in propanol-1 yields propyl propionate and diethyl ketone as products. Phenanthroline and 4-N, N-dimethylaminopyridine were found to be the most effective among the promoters studied. The modification of cobalt dioctacarbonyl with phenanthroline and 4-N, N-dimethylaminopyridine favors an increase in the reaction selectivity with respect to diethyl ketone and propyl propionate, respectively.
[en] Semiempirical (INDO) and ab initio valence only calculations of the electronic structure of Nin and Nin (CO)m clusters support the idea that the bonding with the CO ligands destabilizes the 4s-like MOs of the Nin fragment thus eliminating their contribution to the metal-metal bonding in the carbonylated form. This process is accompanied by a complete quenching of the magnetic moment of the bare cluster. (orig.)
[en] The interaction of carbon monoxide with organo-actinides has recently been shown experimentally, particularly by Cloke and co-workers, to result in coupling to give the oligomeric anions CnOn2- (n = 2, 3, 4). In order to model possible intermediates in reactions of this type, we have used density functional theory to explore the systems (C8H8)Th(CO)n (n = 1 to 5) and (C8H8)2Th2(CO)n (n = 2 to 7) related to the known 'thorocene', (η8 -C8H8)2Th. Thorium was chosen as the actinide for this work since its chemistry almost entirely involves the single diamagnetic +4 oxidation state. All of the binuclear (C8H8)2Th2(CO)n structures found in this work have long Th-Th distances ranging from 4.4 to 5.0 Angstroms suggesting the absence of direct Th-Th bonds. Two (C8H8)2Th2(CO)2 isomers of similar energies in which the two CO groups have coupled to form trans and cis isomers of a bridging η4 -μ-C2O2 ligand are low energy structures. These bridging η4-μ-C2O2 ligands exhibit ultralow ν(CO) frequencies around 1000 cm-1 indicating strong back donation of thorium d and f electrons into C-O antibonding orbitals. Most of the carbonyl richer (C8H8)2Th2(CO)n (n = 3 to 7) structures are derived from one of these basic (C8H8)2Th2(CO)2 structures by addition of terminal CO groups. An exception is the lowest energy (C8H8)2Th2(CO)4 structure which has C4v symmetry with four equivalent separate ν2 -μ-CO groups bridging the thorium atoms. The thermochemistry of these systems suggest (C8H8)Th(CO)4 and (C8H8)2Th2(CO)n (n = 2, 4) to be the most promising synthetic objectives, which are potentially obtainable by reductive carbonylation of the known (C8H8)ThCl2. (authors)
[en] This oral presentation described the intramolecular oxidation of an ansa-chromocene carbonyl complex through the electrophilic addition of a borane to the cyclopentadienyl ring followed by transfer of a proton from the ring to the metal center. A variety of zwitterionic, ring-borylated ansa-chromocene complexes were structurally and physically characterized. [Part of final report for DOE contract FG02-98ER45709.]
[en] The complexes formed by H2CO, CH3CHO, and (CH3)2CO with 1, 2, and 3 molecules of CO2 are studied by ab initio calculations. Three different types of heterodimers are observed, most containing a tetrel bond to the C atom of CO2, and some supplemented by a CH⋅⋅O H-bond. One type of heterodimer is stabilized by an anti-parallel arrangement of the C=O bonds of the two molecules. The binding energies are enhanced by methyl substitution on the carbonyl, and vary between 2.4 and 3.5 kcal/mol. Natural bond orbital analysis identifies a prime source of interaction as charge transfer into the π*(CO) antibonding orbital. Heterotrimers and tetramers carry over many of the geometrical and bonding features of the binary complexes, but also introduce O⋅⋅O chalcogen bonds. These larger complexes exhibit only small amounts of cooperativity
[en] Published data on the methods of synthesis of polycyclic nitramines are analysed. The advantages, drawbacks and prospects of two main approaches to the formation of the molecular cage, namely, amine or amide condensation with carbonyl compounds and consecutive formation of the polycyclic cage with introduction of reactive terminal substituents, are discussed.