(a)

(1)

The chloride salts of the 6-coordinate complexes of manganese(II), iron(II), cobalt(II), nickel(II) and

copper(II) were prepared by reaction with two equivalents of the bisethylenetriamine (tris) ligand in

each case. Write the formula of each complex and indicate the d" configuration.

H

tris

H.

H

H

(i) Estimate the moments for the cobalt and copper complexes in Bohr magnetons.

(Bisethylenetriamine is a weak field ligand).

(5)

(10)

(iii) Sketch the structures of the cobalt and copper complex cations and explain why they are different

in terms of a d-orbital splitting diagram.

(10)

(ii) A portion of the manganese(II) complex described in Section A is oxidised in air over 30 minutes to

yield a brown solid A. A second portion is oxidised with hydrogen peroxide for four hours to yield

blue solid B. Sketch possible X-band EPR spectra for both A and B giving reasons for your

answer.

(12)

(iii) The brown solid A is dissolved in a solution of aqueous sodium chloride in air yielding

[Mn(H₂O),Cl]. Derive the molecular orbital energy diagram for [Mn(H₂O),Cl] using the the

angular overlap method.

(12)/n(v) The manganese(II) complex described in Section A is then reacted with a macrocyclic ligand L to

form a dinuclear complex [Mn₂L]. L is a neutral ligand and the manganese ions are bridged by

two water molecules. The small cavity size of L produces a short Mn-Mn internuclear separation

(2.6 A) and both manganese ions are electronically equivalent. Sketch the predicted X-band EPR

spectrum for the solid dimanganese complex at 77 K giving reasons for your answer. (12)

Nuclear Spin values:

56Fel=0

57 Fel=½

58 Col = 7/2 (100% natural abundance)

55Mn 1 = 5/2 (100% natural abundance)

63Cu 1 = 3/2 (30% abundance)

65Cu 1 = 3/2 (70% abundance)

Naturally abundance nickel isotopes, 5 Ni, Ni and 62Ni 1 = 0