Interesting question. To begin with, SiF₄ does fulfill the definition of Lewis acid because it can accept electron pairs (those from, say, fluoride anions) in a vacant orbital (low lying, energetically available 4p orbitals).
However, a whole bunch of disagreement is still going on as to the real contribution of such AOs to the so-called expanded octet structures: some prefer to describe such compounds as made with remarkable ionic contributions, some say resonance structures become predominant, etc.
All in all, if you consider the existence of real compounds like H₂[SiF₆] or Na₂[SiF₆] (hexafluorosilicic acid and sodium hexafluorosilicate, respectively), you can clearly see both are made of the [SiF₆]²¯ (hexafluorosilicate) anion which is clearly a Lewis adduct.
Interesting question. To begin with, SiF₄ does fulfill the definition of Lewis acid because it can accept electron pairs (those from, say, fluoride anions) in a vacant orbital (low lying, energetically available 4p orbitals).
However, a whole bunch of disagreement is still going on as to the real contribution of such AOs to the so-called expanded octet structures: some prefer to describe such compounds as made with remarkable ionic contributions, some say resonance structures become predominant, etc.
All in all, if you consider the existence of real compounds like H₂[SiF₆] or Na₂[SiF₆] (hexafluorosilicic acid and sodium hexafluorosilicate, respectively), you can clearly see both are made of the [SiF₆]²¯ (hexafluorosilicate) anion which is clearly a Lewis adduct.
Under exited state it's E.C. is 1s2, 2s2 2p6,3s1,3p3
It undergoes sp3 hybridization to give 4 sp3 hybrid orbitals and each hybrid orbital containing 1 electron ,now shares 1 electron from F- to form SiF4 molecule having tetrahedral structure.
Lewis acid can accept a pair of electron from Lewis base. Now in case of SiF4 molecule 3d- orbitals are empty hence it can accept electron pair from Lewis base e.g. F- to give [ SiF6] 2- ion.
On the other hand such process is not possible for compounds formed by 2nd period elements. Hence they can not act as Lewis Acid e.g. CF4 can not act as Lewis acid.
In nut shell presence of d- orbitals is responsible.
Under exited state it's E.C. is 1s2, 2s2 2p6,3s1,3p3
It undergoes sp3 hybridization to give 4 sp3 hybrid orbitals and each hybrid orbital containing 1 electron ,now shares 1 electron from F- to form SiF4 molecule having tetrahedral structure.
Lewis acid can accept a pair of electron from Lewis base. Now in case of SiF4 molecule 3d- orbitals are empty hence it can accept electron pair from Lewis base e.g. F- to give [ SiF6] 2- ion.
On the other hand such process is not possible for compounds formed by 2nd period elements. Hence they can not act as Lewis Acid e.g. CF4 can not act as Lewis acid.
In nut shell presence of d- orbitals is responsible.
Interesting question. To begin with, SiF₄ does fulfill the definition of Lewis acid because it can accept electron pairs (those from, say, fluoride anions) in a vacant orbital (low lying, energetically available 4p orbitals).
However, a whole bunch of disagreement is still going on as to the real contribution of such AOs to the so-called expanded octet structures: some prefer to describe such compounds as made with remarkable ionic contributions, some say resonance structures become predominant, etc.
All in all, if you consider the existence of real compounds like H₂[SiF₆] or Na₂[SiF₆] (hexafluorosilicic acid and sodium hexafluorosilicate, respectively), you can clearly see both are made of the [SiF₆]²¯ (hexafluorosilicate) anion which is clearly a Lewis adduct.
Interesting question. To begin with, SiF₄ does fulfill the definition of Lewis acid because it can accept electron pairs (those from, say, fluoride anions) in a vacant orbital (low lying, energetically available 4p orbitals).
However, a whole bunch of disagreement is still going on as to the real contribution of such AOs to the so-called expanded octet structures: some prefer to describe such compounds as made with remarkable ionic contributions, some say resonance structures become predominant, etc.
All in all, if you consider the existence of real compounds like H₂[SiF₆] or Na₂[SiF₆] (hexafluorosilicic acid and sodium hexafluorosilicate, respectively), you can clearly see both are made of the [SiF₆]²¯ (hexafluorosilicate) anion which is clearly a Lewis adduct.
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E.C. of Si is 1s2,2s2 2p6, 3s2 3p2 3d0
Under exited state it's E.C. is 1s2, 2s2 2p6,3s1,3p3
It undergoes sp3 hybridization to give 4 sp3 hybrid orbitals and each hybrid orbital containing 1 electron ,now shares 1 electron from F- to form SiF4 molecule having tetrahedral structure.
Lewis acid can accept a pair of electron from Lewis base. Now in case of SiF4 molecule 3d- orbitals are empty hence it can accept electron pair from Lewis base e.g. F- to give [ SiF6] 2- ion.
On the other hand such process is not possible for compounds formed by 2nd period elements. Hence they can not act as Lewis Acid e.g. CF4 can not act as Lewis acid.
In nut shell presence of d- orbitals is responsible.
E.C. of Si is 1s2,2s2 2p6, 3s2 3p2 3d0
Under exited state it's E.C. is 1s2, 2s2 2p6,3s1,3p3
It undergoes sp3 hybridization to give 4 sp3 hybrid orbitals and each hybrid orbital containing 1 electron ,now shares 1 electron from F- to form SiF4 molecule having tetrahedral structure.
Lewis acid can accept a pair of electron from Lewis base. Now in case of SiF4 molecule 3d- orbitals are empty hence it can accept electron pair from Lewis base e.g. F- to give [ SiF6] 2- ion.
On the other hand such process is not possible for compounds formed by 2nd period elements. Hence they can not act as Lewis Acid e.g. CF4 can not act as Lewis acid.
In nut shell presence of d- orbitals is responsible.
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In case of silicone halides inductive effect dominate over back bonding hence Lewis acid character decided by inductive effect.
Hence order of Lewis acid character:
[SiF4>SiCl4> SiBr4 > SiI4]
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In case of silicone halides inductive effect dominate over back bonding hence Lewis acid character decided by inductive effect.
Hence order of Lewis acid character:
[SiF4>SiCl4> SiBr4 > SiI4]
Hope you like it
Plz upvote
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SiF4 has the ability to extend the valency beyond four by using its vacant d- orbitals.
For example :
SiF4 +2F- = SiF6^2-
This reaction shows that SiF4 can act as a Lewis acid.
SiF4 has the ability to extend the valency beyond four by using its vacant d- orbitals.
For example :
SiF4 +2F- = SiF6^2-
This reaction shows that SiF4 can act as a Lewis acid.
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A Lewis acid is an electron deficient species which accepts a Lone pair of electrons from a Lewis base.
A Lewis acid is an electron deficient species which accepts a Lone pair of electrons from a Lewis base.
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