A
2
7/21/2019 A http://slidepdf.com/reader/full/a56d6be851a28ab3016927c4e 1/2 A metal on which a surface film forms by natural process or by immersion in a passivating solution, makingWhy do AlCl3 formdimers but BCl3, BF3 not? I knowthat aluminium atom in a AlCl3 molecule would forma dative covalent bondwith thelone pair electrons of another one, using its empty orbital in order to complete an octet structure. But, for its upper element in the same group, boron, why isn't it do the same thing to complete its octet? I... showmore Follow 2 answers Report Abuse Answers Best Answer: I don't think d- orbitals have anything to do with it, sincethere is no need to invoke them in Al2Cl6. Froma molecular orbital point of view, the "donation" fromfluorine or Cl to boron in BF3 or BCl3 is overlap betweenfilled halogen and vacant boron p(pi) orbitals. On thewhole, secondtypical rowelements do not formstrong p(pi) - p(pi) bonds, probably becauseof sizemismatch. (Oops! I rather contradicted myself! Cl does in BCl3, but then of courseCl is the smallest of theseelements). "AlCl3" is an interesting material. It forms ahydrate, [Al(H2O)6]Cl3, whichis an ionic compound, soluble in water. It exists as alayered structure in the solid, whichis usually regarded as ionic. However, the solid readily sublimes to give Al2Cl6, in whichtwo of the chlorines are bridging and have a formal positive charge, Al being tetrahedral. Solutions of "AlCl3" in organic solvents alsohavethis dimeric structure. Facts Matter · 5 years ago 1 Thumbs up 0 Thumbs down Comment Asker's rating Report Abuse •
-
Upload
silokshan-balasingam -
Category
Documents
-
view
216 -
download
0
description
RTRTR
Transcript of A
7/21/2019 A
http://slidepdf.com/reader/full/a56d6be851a28ab3016927c4e 1/2
A metal on which a surface film forms by natural process or by immersion in a passivating
solution, makingWhy do AlCl3 form dimers but BCl3, BF3 not?
I know that aluminium atom in a AlCl3 molecule would form a dative covalent bond with the lone pair
electrons of another one, using its empty orbital in order to complete an octet structure. But, for its upper
element in the same group, boron, why isn't it do the same thing to complete its octet? I...show more
Follow
2 answers
Report Abuse
Answers
Best Answer: I don't think d- orbitals have anything to do with it, since there is no need to invoke them
in Al2Cl6.
From a molecular orbital point of view, the "donation" from fluorine or Cl to boron in BF3 or BCl3 is overlap
between filled halogen and vacant boron p(pi) orbitals. On the whole, second typical row elements do not
form strong p(pi) - p(pi) bonds, probably because of size mismatch. (Oops! I rather contradicted myself! Cl
does in BCl3, but then of course Cl is the smallest of these elements).
"AlCl3" is an interesting material. It forms a hydrate, [Al(H2O)6]Cl3, which is an ionic compound, soluble
in water. It exists as a layered structure in the solid, which is usually regarded as ionic. However, the solid
readily sublimes to give Al2Cl6, in which two of the chlorines are bridging and have a formal positive
charge, Al being tetrahedral. Solutions of "AlCl3" in organic solvents also have this dimeric structure.
Facts Matter · 5 years ago
1
Thumbs up
0
Thumbs downComment
Asker's rating
Report Abuse
•
7/21/2019 A
http://slidepdf.com/reader/full/a56d6be851a28ab3016927c4e 2/2
I think it has to do with aluminum's d orbitals. AlCl3 is a completely different animal than BF3. Fluorine has
been known to donate electrons into a bond because a double bond has a shorter length than a single
bond, so fluorine actuallyis in closer contact to all three electrons. Chlorine doesn't do this because it is
not as electronegative.
the metal resistant to corrosion.
