Spin-quartet ground state

In a simple crystal-field description, a spin-quartet ground state (S = 3/2) of iron(III) is energetically stabilized over the spin-sextet (S = 5/2) when the energy separation... 

The complex [CrH(H20)j]2+ briefly mentioned in the introduction is obtained by pulse radiolysis from aqueous Cr +, but this is an unstable species which decomposes by protonolysis. Its spectroscopic properties are similar to those of the analogous alkyl species, known to adopt a spin quartet configuration [3]. On the other hand, the isoelectronic, sterically protected Tp B CoH complex [Tp -Bu,Me = hydrotris(3- er/-butyl-5-methylpyrazolyI)borate], also having a spin quartet ground state, could be isolated and characterized by X-ray crystallography [85b],... 

In the case of C J, finally, the electron is taken from the MO in the lowest spin singlet state. Since this is a bonding orbital, the bond length is larger than for the neutral molecule, or 1.30 A. There is a lower energy spin quartet ground state with a bond length of 1.40 A. In the latter case, there are only two electrons in the MO. 

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