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Wednesday, August 7, 2019

Sigma Bonded Complexes:

In these complexes, the metal atom and carbon atom of the ligand are joined together with a sigma bond, i.e., the ligand contributes one electron and is, therefore, called one electron donor. Examples are :
(1)  Grignard reagent, R-Mg-X where R is an alkyl or aryl group and  X is a halogen.
(2)  Zinc compounds of the formula R2Zn such as (C2H5)2Zn. This was first isolated by Frankland in 1849. Other similar compounds are Sn(CH3)4, Pb(C2H5)4, Al2(C2H5)6  Al2(CH3)6  , Pb(CH3)4 etc.
      Al2(CH3)6 is a dimeric compound and has a structure similar to diborane, B2H6 It is an electron deficient compound and two methyl groups act as bridges between two aluminium atoms.

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