Three-center four-electron Bridge bond (3C-4e Bond): Structure of AlCl3:

(1) Al₂Cl₆ is neither hypovalent nor hypovalent rather its octet is complete. We will used  MOT here  it cannot act as Lewis acid  due to crowding in spite having vacant d orbital’s   however AlCl₃  act as Lewis acid .

(2) Al₂Cl₆ contains six bonds having two bridge bonds (3c-4e) and four bonds is (3C-4e) bridge bonds are lies perpendicular to plane.

(3) The bond lengths of terminal Al−Cl bonds are shorter (206 pm) while bond length of bridged Al−Cl bonds are longer (221 pm) and also outer bond angle (Cl−Al−Cl) are greater (118) than inner bond angle (Al−Cl−Al).

(4) Maximum six atoms are lies in same plane which four terminal Cl and two aluminium atoms.

(5) AlCl₃ in vapor phase or in non-polar solvent is dimeric Al₂Cl₆ hence sp3 hybridised having 3c-4e bonds.

Related Questions: 

(1) Why aqueous solution of AlCl3 is acidic in nature ?

(2) What happen when aq AlCl3 react with Acid or Base?

(3) Although anhydrous aluminium chloride is covalent but its aqueous solution is ionic in nature. Why?

(4) Why BF3 do not exist as dimer?. Explain.

(5) Why B-F bond length in BF3 is shorter (130 pm) than B-F bond Iength in BF4- (143 pm)?. Explain.

(6) B-F bond length in BF3 is shorter than B-F bond length in (BF4)- why?

(7) When B2H6 is allowed to react with following Lewis bases, then how may given Lewis base form adduct through symmetrical Cleavage of B2H6.

(8) What is product of reaction between diborane (B2H6) and ammmonia (NH3)?

(9) Why methylation of Diborane (B2H6) replace four hydrogen only ?

(10) What is Use of Boric Acid?

(11) What is use of Orthoboric acids?

(12) What is basicity of "Boric acid" ?

(13) Why Boric acid exist in solid state ?

(14) What is structure of solid Ortho Boric acid ?

(15) What is effect of heat on Borax?

(16) What is the structure of trimetaboric acid and trimetaborate ion?

(17) What is the Sodium per borate ,give the structure and its uses?

(18) Why aqueous solution of borax reacts with two moles of acids ?

(19) What is the molecular formula of Borax ?

(20) Why Boric acid become strong acid in the presence of cis 1,2-diol or 1,3-diol ?

(21) Why Borazine is more reactive than benzene towards Electrophic Aromatic substitution reactions ?

(22) Why Borazine (B3N3H6) is also known as inorganic benzene ?.

(23) Four-center two-electron bond (4C-2e Bond): Structure of AlCl3:

(24) What is the difference between the structure of AlCl3 and diborane?