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The system most often studied for the cis effect is an octahedral complex M(CO) 5 X where X is the ligand that will labilize a CO ligand cis to it. Unlike the trans effect, which is most often observed in 4-coordinate square planar complexes, the cis effect is observed in 6-coordinate octahedral transition metal complexes.
Very often, cis–trans stereoisomers contain double bonds or ring structures. In both cases the rotation of bonds is restricted or prevented. [4] When the substituent groups are oriented in the same direction, the diastereomer is referred to as cis, whereas when the substituents are oriented in opposing directions, the diastereomer is referred to as trans.
In an octahedral complex, this degeneracy is lifted. The energy of the d z 2 and d x 2 − y 2 , the so-called e g set, which are aimed directly at the ligands are destabilized. On the other hand, the energy of the d xz , d xy , and d yz orbitals, the so-called t 2g set, are stabilized.
The descriptors cis (Latin, on this side of) [2] and trans (Latin, over, beyond) [3] are used in various contexts for the description of chemical configurations: [4] [5] In organic structural chemistry , the configuration of a double bond can be described with cis and trans , in case it has a simple substitution pattern with only two residues.
The ligand can bend so that one donor atom is at the pole and the remaining three are on the equator of the central atom. This is called cis-β (beta). The remaining octahedral positions are cis (adjacent) to each other. The triangles of coordinating atoms and the central atom have two coplanar atoms, and one perpendicular atom.
Chemical nomenclature, replete as it is with compounds with very complex names, is a repository for some names that may be considered unusual. A browse through the Physical Constants of Organic Compounds in the CRC Handbook of Chemistry and Physics (a fundamental resource) will reveal not just the whimsical work of chemists, but the sometimes peculiar compound names that occur as the ...
A superscripted uppercase "C" denotes complex conjugation. The two rightmost columns indicate which irreducible representations describe the symmetry transformations of the three Cartesian coordinates ( x , y and z ), rotations about those three coordinates ( R x , R y and R z ), and functions of the quadratic terms of the coordinates( x 2 , y ...
In chemistry, dissociative substitution describes a reaction pathway by which compounds interchange ligands. The term is typically applied to coordination and organometallic complexes, but resembles the S N 1 mechanism in organic chemistry. This pathway can be well described by the cis effect, or the labilization of CO ligands in the cis position.