Rhenium complexes carbonylation

Schiff bases provide useful mixed donor sets. The carbonyl function of the most frequently used ligands is derived from either 1,3-dicarbonyl compounds or salicylaldehyde. Favourable combinations involve O-, N- and S-donor atoms. A range of technetium and rhenium complexes exist with bi-, tri-, tetra- and pentadentate ligands. The geometry of these complexes depends on the number and type of coordinating atoms as well as on the chain length between the donor atoms in the SchifF-base ligands. 

Nagata, T., Pohl, M., Weiner, H., and Finke, R.G., Polyoxoanion-supported organometallic complexes carbonyls of Rhenium(I), Iridium(I), and Rhodium(I) that are soluble analogs of solid-oxide-supported M(CO) + and that exhibit novel M(CO)n+ mobility, Inorg. Chem., 36, 1366, 1997. 

The photochemistry of rhenium complexes occupies a prominent position in the photochemistry of transition metal complexes. Along with early preparative studies on photosubstitution of carbonyl species like Re(CO)sX, the preparation of the remarkably stable yellow complex /ac-Re(CO)3(phen)Cl foreshadowed the discovery of the a large class of related luminescent materials by Wrighton and co-workers in the 1970s [ 1 ]. As pointed out by Vogler and Kunkley, the current photochemistry of rhenium complexes is rich, spanning eight oxidation states from formal Re(0) (for example, Re2(CO)io) to formal Re(VII) (for example MeReOs) [2],... 

Table 3 Rhenium complexes with less then three carbonyl groups ...

Photolysis of Cp Mn(CO)3 in THF leads to the solvent complex Cp Mn-(CO)2(THF). Removal of solvent at -20°C followed by warming to room temperature while maintaining reduced pressure results in dimerization of solvent complex, decarbonylation, and solvent loss to form the air-sensitive 8 (17,51,88). While not isolated, the related Cp complex 8 has been observed in the gas phase. It is seen, in the electron-impact mass spectrum of the THF complex CpMn(CO)2(THF), which shows a molecular ion and cracking pattern assignable to 8 rather than the THF complex itself (51). The rhenium complex 9 is formed on photolysis of Cp Re-(CO)3 in THF (18) and in the carbonylation (15-20 atm, THF or toluene) of Cp 2Re2(0)2(ju.-0)2 (89,90). 

Scheme 9.1 Preparation of the methylmanganese and -rhenium complexes 2a,b from the pentacarbonyl metallates la,b and their conversion into the acyl metal derivatives 3 (L = CO, PR3, NH2R) via migratory insertion of a carbonyl ligand into the M—CH3 bond (a M = Mn b M = Re)...

Since cobalt carbonyl anions react readily with a large variety of cyclopropenylcarbonyl chlorides to give selectively / -oxocyclobutenyl complexes (equation 198), it was suggested that reactions of cyclopropenylium cations and [Co(CO)4] involve direct electrophilic attack at the CO ligand rather than at cobalt . However, observation of ring expansion products in the -cyclopropen-3-yl rhenium complex (vide suggests that an... 

The MLCT emission properties of many rhenium(I) carbonyl diimine complexes have been used to demonstrate the energy-gap law. For example, the complexes [Re(N-N)(CO)3(L)] (N N = bpy, phen, 5-Ph-phen L = substituted pyridines or quinoline) displayed MLCT (d7r(Re)- 7t (N-N)) phosphorescence at room temperature. The radiationless decay-rate constants depended on the emission energy as described in the energy-gap law (Inknr A-B fern) From the Hammett constant of the substituent, both the emission energy and hfetime of related complexes can be predicted. ... 

When more conjugated diimine or pyridine ligands are used, the excited states of rhenium(I) carbonyl complexes can have substantial IL character. While the MLCT emission is often broad, with a lifetime in the submicrosecond to microsecond timescale, the IL emission usually has noticeable structural features, even in fluid solutions at ambient temperature. The emission lifetime is usually very long. A simple and widely applicable approach is to evaluate the ratio of the emission quantum yield and the emission lifetime (the product of the intersystem crossing efficiency and radiative decay-rate constant). Experimental values of... 

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