Quadruple bonding to main group elements is extremely rare although they have four valence orbitals accessible for bonding. Here we report the unprecedented quadruple bonding between a carbon atom and a transition metal fragment Fe(CO)3 based on high level theoretical calculations. Various bonding analyses reveal the unprecedented nature of the C[quadruple bond, length as m-dash]Fe quadruple bonding interaction. The validity of the single electron transmutation concept has been tested which fruitfully reproduces the structural and bonding similarities between the two neighbours in the periodic table.