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Two enantiomeric pair in which all three pairs of identical ligands are cis. These are equivalent to the Δ vs Λ isomers mentioned above. The number of possible isomers can reach 30 for an octahedral complex with six different ligands (in contrast, only two stereoisomers are possible for a tetrahedral complex with four different ligands).
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.
In inorganic complex chemistry, the descriptors cis and trans are used to characterize the positional isomers in octahedral complexes with A 2 B 4 X configuration or square planar complexes with A 2 B 2 X configuration.
Cis and trans isomers occur both in organic molecules and in inorganic coordination complexes. Cis and trans descriptors are not used for cases of conformational isomerism where the two geometric forms easily interconvert, such as most open-chain single-bonded structures; instead, the terms " syn " and " anti " are used.
The rate of reductive elimination is greatly influenced by the geometry of the metal complex. In octahedral complexes, reductive elimination can be very slow from the coordinatively saturated center; and often, reductive elimination only proceeds via a dissociative mechanism, where a ligand must initially dissociate to make a five-coordinate ...
The insertion of carbon monoxide into a metal-carbon bond to form an acyl group is the basis of carbonylation reactions, which provides many commercially useful products. Mechanistic studies reveal that the alkyl group migrates intramolecularly to an adjacent CO ligand. [2] [3] CO Insertion reaction pathway for an octahedral complex
octahedral, trans-bicapped Ni in nickel arsenide, NiAs; 6 As neighbours + 2 Ni capping [8] 8 trigonal prismatic, triangular face bicapped Ca in CaFe 2 O 4 [3] 9 tricapped trigonal prismatic [ReH 9] 2− in potassium nonahydridorhenate [2] [Th(H 2 O) 9] 4+ aqua complex [6] SrCl 2 ·6H 2 O, Th in Rb[Th 3 F 13] [3] 9 capped square antiprismatic
With metals in group 4 or 5 a so-called edge-capped octahedral clusters are more common. Twelve halides are located along the edge of the octahedron and six are terminal. Examples of this structure type are tungsten(III) chloride, Ta 6 Cl 14 (H 2 O) 4, [5] [6] Nb 6 F 15, and Nb 6 F 18 2−. [1] Structure of edge-capped octahedral clusters such ...