CCL: The multiplicity of Ni(H2O)62+?

[Heath Watts <hdw115[]psu.edu>]

 Hi Sayed,

To form Ni(2+), two electrons are lost from neutral nickel to
 form the cation. For the first row transition elements, the d-orbitals are
 considered filled, prior to the previous s-orbitals. For your example, the
 electron configuration notation for neutral nickel would be [Ar]3d(10) rather
 than [Ar]4s(2)3d(8). Therefore, when Ni ionizes to form Ni(2+), it loses two of
 its ten d-electrons, one from each of two d-orbitals to give Ni(2+) with an
 electron configuration of  [Ar]3d(8). The nickel cation now has two
 unpaired electrons (see Hund's rule), each with a spin of +1/2 or -1/2. 
 
To find the multiplicity for your model, use the equation multiplicity=2S+1,
 where S is the total spin for your model. For example, if both electrons have
 the same spin of +1/2, then multiplicity=2(1/2 + 1/2)+1=3. If they have opposite
 spins then multiplicity=2(-1/2 + 1/2)+1=1. Therefore, Ni(2+) is in the singlet
 state if the two unpaired electrons have opposite spins: (+1/2, -1/2) or (-1/2,
 +1/2), and in the triplet state if they have the same spin: (+1/2, +1/2) or
 (-1/2, -1/2).
 
Most inorganic chemistry books provide thorough explanations of oxidation
 states and multiplicity for the first transition element series. I like this
 one: 
Cotton, F.A.; Wilkinson, G.; Gaus, P.L. The elements of the first
 transition series. In Basic Inorganic Chemistry. Wiley, NYC, 1987, pp
 473-515
 
Heath

On Mon, Aug 23, 2010 at 10:45 AM, Sayed Mesa elsayed.elmes-x-yahoo.com <owner-chemistry,,ccl.net> wrote:

Sent to CCL by: "Sayed  Mesa" [elsayed.elmes[-]yahoo.com]
Dear CCL community

I am confused about what the right spin multiplicity of [Ni(H2O)6]2+? Is it singlet or triplet? This confusion comes from two approaches:

(i)The total number of electrons in the molecule is 86 electrons. Then the spin multiplicity is singlet;

(ii) The another approach if we consider the 8 electronic configurations of Ni2+ ion so the number of unpaired electron is 2 so the spin multiplicity is triplet.

Which approach is right???

Thanks
Sayed



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