Complexes carbonyl carbide

Fig. 35. Skeletal structures of the rhodium-carbonyl carbide complexes Rh8(CO)i9C and [Rhis(CO)28C2]- (7).

Veillard [19] covers a similar range of molecules but from the Hartree-Fock and post-HF view. The discussion is organised more in terms of molecular properties. Thus, he deals with metal carbonyls, carbides, cyanides, C02 complexes, alkyls, carbenes, carbynes, alkenes, alkynes and metallocenes under the headings of electronic states, electronic spectra, optimised geometries, binding energies, Ionisation Potentials and Electron Affinities, nature of M-L bonding and other properties (e.g. vibrational spectra, dipole moments and electron distributions). 

Chisholm and his group recently succeeded in transforming a metal carbonyl into a stable fi4-carbido complex W4( 4-C)(/t-NMe)(0-i-Pr)12 1 The 13C-NMR signal for the (/ 4-C)4 ligand is 366.8 ppm [5] which can be considered as a realistic model of a surface bound carbido species in the sense of the original proposal by Fischer and Tropsch (Fig. 2). Upon addition of hydrogen, surface bound carbide can be stepwise transformed into methane. 

Cobalt carbonyls are the oldest catalysts for hydroformylation and they have been used in industry for many years. They are used either as unmodified carbonyls, or modified with alkylphosphines (Shell process). For propene hydroformylation, they have been replaced by rhodium (Union Carbide, Mitsubishi, Ruhrchemie-Rhone Poulenc). For higher alkenes, cobalt is still the catalyst of choice. Internal alkenes can be used as the substrate as cobalt has a propensity for causing isomerization under a pressure of CO and high preference for the formation of linear aldehydes. Recently a new process was introduced for the hydroformylation of ethene oxide using a cobalt catalyst modified with a diphosphine. In the following we will focus on relevant complexes that have been identified and recently reported reactions of interest. 

Heteronuclear Pt-Ru binary carbonyl clusters have been used for the preparation of tailored PtRu bimetallic electrocatalysts. The use of carbonyl complexes such as Ru4Pt2(CO)i8 and closely related carbide and hydride carbonyl-derived clusters, that is, Ru5PtC(CO)i6 and Ru6Pt3(CO)2i( X3-H)( x-H)3, has allowed the preparation of carbon- and y-Al203-supported catalysts in which the presence of RugPts, RusPt and Ru4Pt2 clusters or nanoparticles has been reported [62-65]. 

Pair-of-dimer effects, chromium, 43 287-289 Palladium alkoxides, 26 316 7t-allylic complexes of, 4 114-118 [9JaneS, complexes, 35 27-30 112-16]aneS4 complexes, 35 53-54 [l5]aneS, complexes, 35 59 (l8)aneS4 complexes, 35 66-68 associative ligand substitutions, 34 248 bimetallic tetrazadiene complexes, 30 57 binary carbide not reported, 11 209 bridging triazenide complex, structure, 30 10 carbonyl clusters, 30 133 carboxylates... 

The smallest member of the iron carbide family is neither a carbonyl nor a cluster, but is included here since its structure is an example of the lowest coordination number for a carbon atom in a transition metal complex. The... 

While DFT may or may not be more accurate than MP2 for absolute shielding calculations is debatable, the strength of the DFT method in calculations of shieldings is in the ability of DFT to provide a consistent picture over a wide range of chemical systems, since calculations can be done at a very modest computational cost compared to MP2. Among the successes of the method is in ligand chemical shifts in transition metal complexes. For example, 13C, 170,31P and H chemical shifts for oxo (12,14,15), carbonyl (16-19), interstitial carbide (20), phosphine (21,22), hydride (23), and other ligands have been successfully reproduced to within tens of ppm in... 

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