Why transition elements show tendency to form large number of complexes??

2 Answers
Aug 12, 2017

Answer:

It is because the transition metals have variable oxidation states.

Explanation:

The transition elements span from group 3 to 11.They show variable oxidation states according to the catalyst, reacting element or compound, and the conditions of the reaction they are participating in.Thus, they can form a large number of complex compounds

They also form coordination compounds which have #d_(pi) - d_(pi)# overlap of orbitals.

Aug 13, 2017

It's because they have #d# orbitals, which are naturally oriented along all the coordinate axes in ways that are convenient for forming many #sigma# bonds and some #pi# bonds.

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Some examples...

  • The #d_(z^2)# and #d_(x^2 - y^2)# are useful for #sigma# bonding along the coordinate axes.

Inorganic Chemistry, Miessler et al.

  • The #d_(xy)#, #d_(xz)# and #d_(yz)# can be used for #pi# bonding on octahedral complexes.

https://organometallicchem.files.wordpress.com/

The right-hand side of the diagram illustrates #pi# bonding with ethene using a #d_(xy)# orbital, and the left-hand side is a #sigma# bond with ethene using a #d_(x^2-y^2)# orbital.

This kind of bond is known to rotate at low temperatures, and thus, variable-temperature NMR is useful in identifying such complexes.