Organometallic complexes isomers

The organometallic complexes of these metals with thiocyanate are important because linkage isomers have been obtained (690). Some of the relevant compounds are included in Table XXIII. The compound 7T-cpW(CO)gSCN, which was characterized by the positions of its CN and CS frequencies and by the integrated intensity of the former, resists all attempts to convert it to the A-thiocyanato isomer, unlike... 

There are many examples of redox-induced structural rearrangements in organometallic complexes the reader is referred to a review by Connelly. The simplest rearrangement is cis/trans or fac/mer isomerization, usually induced by oxidation. Thus, cw-[Mn(CO)2(dppe)2] slowly converts to the trans isomer with a rate constant of 10 s at room temperature. Upon oxidation, the cis — trans isomerization increases in rate by 7 powers of 10. The process is not catalytic, so that stoichiometric oxidation followed by reduction is required to synthetically utilize the increased reactivity of the radicals in the conversion of 18-electron cis-[Mn(CO)2(dppe)2l to frani-[Mn(CO)2(dppe)2]. An example of oxidatively induced fac mer isomerization is given in Scheme 10. The fac mer reaction for the neutral 18-electron isomer is slow, with 2 = 2 X 10 s , K2 = 4. The reaction fac mer is much faster and... 

The phenomenon of isomerism is of fundamental importance in chemistry. It has dominated orgaiuc chemistry for over a century and also plays a role in many classes of inorganic compounds especially in organometallic complexes. Owing to the directional and localized character of simple covalent bonds, a collection of atoms may be hnlced in several nonisomorphic ways. This ves rise to the appearance of isomers. 

Recently Ferber et al synthesized organometallic complexes bearing a formyl-cyclopentadienyl connected to Ci7 via an ethynyl linkage. The compounds possess a metallocene planar chirality that is not in any way natural [136,137]. The aim was to see whether the estradiol a- and p-receptors were capable of distinguishing between the two chiral species, as either 1,2- or 1,3-disubstituted isomers. Compounds such as the following were studied [138]. 

Fig. 10.12 Ferrocifen derivative (Z isomer), 3, docked at the estrogen protein receptor site and shows the organometallic complex inside the antagonist binding site of the estrogen receptor.

There is now a growing literature of nickel organometallic complexes that contain carbon dioxide or related cumulene ligands that result from reactions with carbon monoxide. The first structurally characterized complex of carbon dioxide was the nickel complex Ni(G02)(PCy3)2 reported in 1975. A more recent study of this complex provides the complete assignments of the vibrational spectra and theoretical calculations of different isomers in support of a mechanism for CO2 fluxionality that involves end-on coordination. The tridentate pincer ligand 2,6-bis((diiso-propylphosphino)methyl)phenyl (PGP) has been used to form the square-planar Ni(ii) hydroxide complex Ni(OH)(PGP). The complex Ni(OH)(PCP) reacts with CO to give a binuclear /X-GO2 complex (Equation (2)). 

Organometallic complexes of the 5d elements are generally more stable than their Ad analogues. Because of this, isolation and full structural characterization of two catalytic intermediates of the Cativa process, 4.11 and 4.15, are possible under optimized conditions. In the absence of additional CO, two isomers of the neutral complex 4.17, which is a dimer of 4.12, can also be isolated and characterized. 

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