Chromium complexes configurational stability

It has already been stated that chromium complexes of tridentate metallizable azo compounds occupy their position as the single most important class of metal complex dyestuffs because of their high stability. It should be noted, however, that in this context the term stability is not used in the thermodynamic sense but relates to the kinetic inertness of the complexes.25 Octahedral chromium(III) complexes have a tP electronic configuration and the ligand field stabilization energy associated with this is high.26 Ligand replacement reactions involve either a dissociative... 

The reactivity of Cr complexes is marked by very slow Ligand Substitution reactions, resulting in unusual configurational stability. Many chiral complexes have been resolved. There has been a recent resurgence of interest in organochrominm(III) complexes, owing to the importance of chromium in catalytic processes see Chromium Organometallic Chemistry). 

The remarkable chemical and configurational stability of octahedral Cr complexes see Octahedral) was responsible for their role in the groundbreaking work of Alfred Werner, the father of modern coordination chemistry (see Coordination Chemistry History). In the twentieth century, the same properties led to their use in studies of the reaction mechanisms of metal complexes. In recent years, the chemistry of the chromium-carbon bond has been the most active area of research in chromium chemistry see Chromium OrganometalUc Chemistry), motivated in part... 

Ground-state electronic configuration is ls 2s 2p 3s 3p 3i 4s. Manganese compounds are known to exist in oxidation states ranging from —3 to +7 (Table 2). Both the lower and higher oxidation states are stabilized by complex formation. In its lower valence, manganese resembles its first row neighbors chromium and especially iron ia the Periodic Table. Commercially the most important valances are Mn, Mn ", or Mn ". ... 

Chromium hexacarbonyl generally reacts with arenes and is stabilized as the tricarbonyl complex. Hexamethyl bicycio [2.2.0] hexa-2,5-diene chromiumtetracarbonyl is an unusual example of a stabilized chromiumtetracarbonyl. The x-ray pattern reveals a C2 symmetry (Fig. 5-13). This particular bicycio [2.2.0] diene system may effect the stabilization of the electron configuration of the complex. 

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