Carbonyl complexes bridging

Papers dealing with the general reactions of phosphorus group ligan s in the realm of the metal carbonyls are also represented in this report. Basolo and co-workers have examined the kinetics of CO substitution in a number of iridium carbonyl complexes and have found the first examples of a dissociative mechanism for CO substitution in the cobalt triad carbonyl complexes. Bridged diarsinidene complexes are also reported. ... 

Structure. The CO molecule coordinates in the ways shown diagrammaticaHy in Figure 1. Terminal carbonyls are the most common. Bridging carbonyls are common in most polynuclear metal carbonyls. As depicted, metal—metal bonds also play an important role in polynuclear metal carbonyls. The metal atoms in carbonyl complexes show a strong tendency to use ak their valence orbitals in forming bonds. These include the n + 1)5 and the n + l)p orbitals. As a result, use of the 18-electron rule is successflil in predicting the stmcture of most metal carbonyls. 

Dinuclear iron carbonyl complexes with nitrogen containing bridges. A. N. Nesmeyanov, M. I. Rybinskaya and L. V, Rybin, Russ. Chem. Rev. (Engl. Transl.), 1979,48, 213-227 (123). 

A key step proposed in the radical chain mechanism for the formation of the formyl complex is the coordination of CO to the Rh(OEP)- monomer, to give an intermediate carbonyl complex, Rh(OEP)(CO)- which then abstracts hydride from Rh(OEP)H to give the formyl product.This mechanism was proposed without direct evidence for the CO complex, and since then, again from the research group of Wayland, various Rh(fl) porphyrin CO complexes, Rh(Por)(CO), have been observed spectroscopically along with further reaction products which include bridging carbonyl and diketonate complexes. 

Mathur, Pradeep, Chalcogen-Bridged Metal-Carbonyl Complexes. 41 243... 

While essentially all the metal carbonyl complexes for group 4B contain terminal CO ligands, only recently have some bonafide doubly bridging carbonyl complexes been reported. However, these complexes are hetero-nuclear, since the carbonyl ligand bridges a zirconium atom with the metal center of a late transition metal. 

The only Zr(0) carbonyl complex has been prepared by Wreford and co-workers. When ZrCl4 was treated with l,2-bis(dimethyl-phosphino)ethane (dmpe), and then subsequently reduced with sodium amalgam in the presence of 1,3-butadiene, the dmpe bridged dimer, [(t/-C4H6)2Zr(dmpe)]2(dmpe) (65), resulted (114). The brown crystalline dimer 65 was found to be in equilibrium with the 16-e- coordinatively unsaturated complex, (tj-C4H6)2Zr(dmpe) (66), and free dmpe. When toluene solutions of 65 were exposed to CO at —45°C, 1 equivalent of CO per equivalent of Zr was consumed and the CO adduct (r/-C4H6)2Zr-(dmpe)(CO) (67) precipitated as a yellow solid. If these mixtures were allowed to warm above -22°C under vacuum, the precipitate dissolved and the consumed CO evolved (114). Complex 67 could be isolated by... 

The effect from the top is behind the differences in IR spectra of CO adsorbed on various Na-zeolites (Fig. 1). The IR spectrum of CO adsorbed on the high-silica Na-FER shows only one band (centred at 2175 cm 1) that is due to the carbonyl complexes formed on isolated Na+ sites. When the content of Na+ in the sample increases (Na-FER with Si/Al=8), in addition to the band at 2175 cm 1 a new band at 2158 cm"1 appears due to the formation of linearly bridged carbonyl complexes on dual cation sites. The IR spectrum of CO adsorbed on Na-A,which has a large concentration of Na+ cations, shows bands centred at 2163, 2145, and 2129 cm 1 the band at 2163 cm"1 is due to the carbonyl species formed on dual cation sites, while bands at 2145 and 2129 cm"1 are due to carbonyls formed on multiple cation sites (Table 1), i.e., on adsorption sites involving more than two cations. 

Combination of IR spectroscopy and DFT calculations provides evidence that heterogeneous dual cation sites can be formed in zeolites. Bridged carbonyl complexes can be formed whenever two metal cations are at the right distance apart from each other and give rise to a low energy CO stretching band in IR spectra. 

Dinuclear Ru and Os complexes containirm halo bridges include a number of fluoro carbonyl complexes, described in the last section. The reactions between anhydrous HF and [MH2(CO)2(PPh3)2] (M = Ru, Os) produce cix,cA,tra i-[MF2(CO)2(PPh3)2], but when the precursor is [MH2(CO)(PPh3)3], the dinuclear complexes [M2(CO)2(PPh3)4(/u-F)3]" result. Initially, these form as the [Hp2] salts, but are better isolated as the air-stable [BPh4] salts. " ... 

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