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9.
2.
2 Hybridization of the central valence layer orbit
If the valence layer orbitals of the central atoms (or ions) involved in the hybridization belong to the same main layer, that is, ns np nd hybridization, the complexes formed are called external orbital complexes; if the valence layer orbitals of the center participating in the hybridization do not belong to the same The main layer, that is, (n-1)d ns np hybridization, the complex formed is called the inner orbital complex
.
1.
ns np nd hybridization
[Example 9-1] Discuss the bonding and configuration of [FeF 6 ] 3-
.
The electronic configuration of Fe 3+ is 3d 5 , and the following hybridization is carried out during the formation of [FeF 6 ] 3-
The center adopts sp 3 d 2 hybridization, and the 6 hybrid orbitals point to the apex of the regular octahedron
.
The electron of each F - is coordinated to the empty hybrid orbital, thus forming a coordination unit of [FeF 6 ] 3- octahedral configuration
.
[Example 9-2] Discuss the geometric configuration of the hybridization of the central atom of [Ni(CO) 4 ] and the coordination unit
.
Solve the Ni electronic configuration 3d 8 4s 2
Under the action of the ligand CO, the valence layer electrons of Ni are rearranged into 3d 10 4s 0 , 1 4s orbital and 3 4p orbitals are sp 3 hybridized, and the 4 hybridized orbitals point to the apex of the regular tetrahedron, thus [ Ni(CO) 4 ] has a regular tetrahedral structure
.
The common point of [FeF 6 ] 3- and [Ni(CO) 4 ] is that the electron pair of the ligand is coordinated into the outer empty orbital in the center, that is, the ns np nd hybrid orbital, forming an outer orbital complex
.
The resulting coordination bond is called the electricity price coordination bond, and the electricity price coordination bond is weak
.
The difference between [FeF 6 ] 3- and [Ni(CO) 4 ] is that CO ligands can rearrange the valence electrons in the center.
Such ligands are called strong ligands
.
F-isoligands cannot rearrange the valence electrons in the center and are called weak ligands
.
Most ligands are weak ligands, such as F.
- , CI - , H 2 O, C 2 O .
NH 3 , en, etc.
are moderately strong ligands
.
For different centers, the strength of the ligand is different
.
2.
(n-1)d ns np hybridization
[Example 9-3] Discuss the hybridization of the [Fe(CN) 6 ] 3- center ion and the geometric configuration of the complex ion
.
Solution Fe 3+ electronic configuration is 3d 5
.
CN - is a strong ligand, which can rearrange the 5 d electrons of Fe 3+ , and the free 2 3d orbitals participate in the hybridization, and the center adopts d 2 sp 3 hybridization, so [Fe(CN) 6 ] 3- It is a regular octahedron configuration
.
[Example 9-4] Discuss the hybridization of the [Ni(CN) 4 ] 2- central ion and the geometric configuration of the complex ion
.
The electronic configuration of Ni 2+ is 3d 8
.
CN - is a strong ligand, rearranges the d electrons of Ni 2+ , and the free 3d orbital participates in the hybridization, the center adopts dsp 2 hybridization, and the complex ion [Ni(CN) 4 ] 2- is a square configuration
.
The hybrid orbitals of [Fe(CN) 6 ] 3- and [Ni(CN 4 )] 2- both use the inner (n-1)d orbital, and the electron pair of the ligand fits into the inner inner layer of the center with low energy , Forming an inner rail-type complex
.
The resulting coordination bond is called a covalent coordination bond, and the covalent coordination bond is stronger
.
The formation of an outer orbital complex or an inner orbital complex is related to the strength of the ligand, the electron configuration of the valence layer of the central atom or ion, and the number of charges
.
Strong ligands, such as the CN - , NO 2- , and the like easy to form CO.
'S inner-sphere complexes; weak ligands, such as H 2 O, and so easy to form the outer rail X-type complex
.
The central atom or ion with the (n-1)d 10 configuration can only use the outer orbital to form the outer orbital complex; the center of the (n-1) d~3 configuration usually forms the inner orbital complex; n-1) The center of d4~7 configuration can form inner orbital complexes; (n-1) the central ions of d8 configuration Au 3+ , Pt 2+ , Pe 2+ form inner orbital complexes , Ni 2+ forms an inner orbital complex with strong ligands
.
The higher the charge number of the central ion, the stronger the attraction to the coordination atom, and the easier it is to form an inner orbital complex; while the more electronegative coordination atom is easier to form an outer orbital complex
.
