How are metal carbonyls classified depending on the number of metal atoms?

Explanation

metal carbondyls are classified in two different ways as described below
Classification based on the number of metal atoms presents
a. Mononuclear carbonyls
These compounds contains only one metal atoom. For example , `[Ni (CO)_4]^(-) ` nickel tetracarbonyl is tetrahedral `[Fe(CO)_5]-` iron pentacarbonyl is trigonalbipyramidal and ` [Cr(CO)_6]`- Chromium hexacarbonyl is octahedral
b. Poly nuclear carbonyls.
Metallic carbonyls containing two or more metal atoms are called poly nuclear carbonyls , Poly nuclear metal carbonyls may be Homonuclear ` [CO_2(CO)_8],[Mn_2(CO)_(10) ],[Fe_3(CO)_(12) ]` or hetero nuclear `[MnCO(CO)_9) ],[MnRe(CO)_(10) ]` etc.