My problem was [Co(H 2 O) 6 ] +3 Step 1: Determine the charge of the transition

Question

My problem was [Co(H2O)6]+3

Step 1: Determine the charge of the transition metal.

Step 2: Draw splitting diagram.

Step 3: Determine ligand strength.

Step 4: Place electrons into orbitals and label them.

Step 5: Determine what color is absorbed and which color appears, determine whether the complex is low spin or high spin, and determine whether or not the complex is attracted to a magnetic field.

So that we are all on the same page we will use the following electrochemical series, taken from page 1070 of Tro.

CN -1 > NO2-1 > en > NH3 > H2O > OH -1 > F -1 > Cl -1 > Br -1 > I -1

For the octahedral field splitting diagrams: be sure to show and annotate how you determine the following in your problem solving process: The number of electrons, the splitting pattern, the filling of electrons, high spin or low spin, what general colors the complex would absorb, what it would emit, divided by "ROY" and "BIV". Be sure to annotate and be clear why and how you came to the decisions you did!

Explanation / Answer

Step 1: Determine the charge of the transition metal.
charge/oxidation no of Co = x, Oxidation no of H2O = 0, x+0=3, x = 3

Step 2: Draw splitting diagram.
Co contains 7d electrons
Co+3 will contain 6d electrons

Since H2O is a weak field ligand, so octahedral splitting energy D0 is less than pairing energy(P).
DO < P(pairing energy)
So it will form high spin complex.
So the electronic configuration t2g(4) eg(2)
CFSE = -4*2/5*D0 + 2*3/5*D0 + P = -2/5*D0 + P

splitting diagram:

splitting diagram:

eg(2)     (|) (|)

t2g(4)    (||) (|) (|)

Step 3: Determine ligand strength.
H2O is a weak ligand as it is in the middle of the spectrochemical series.

Step 4: Place electrons into orbitals and label them.
t2g(4) eg(2)

Step 5: Determine what color is absorbed and which color appears,
determine whether the complex is low spin or high spin, and
determine whether or not the complex is attracted to a magnetic field.

Color: wavelength of light absorbed (600nm)
color of light absorbed orange, color appears blue

spin: High spin

magnetic property: 4 unpaired electrons: paramagnetic, so the complex is attracted to a magnetic field

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