1.(a) Calculate the gas phase or free ion term for Cr3+ and write down the term symbols expected when the symmetry is reduced to Oh or Td.
(b) By using a conï¬guration diagram in the appropriate symmetry for each complex, determine the ground and excited state terms for [CrCl4]â and [CrCl6]3â and hence predict the UV/visible spectrum of each species. Draw an energy level diagram for each species, marking each level with the correct term symbol and show the transitions between the terms.
(c) Calculate the free ion terms for Fe2+ and Cr2+. When placed in a tetrahedral ï¬eld, predict the symmetry of the terms for the ground and excited state or states. Which of these ions in tetrahedral symmetry will have an orbital contribution to observed magnetic moment in principle?
(d) The ligand ï¬eld splitting in[FeCl4]2â is found to be4000 cmâ1. From this value of âT, calculate the value of âO, the ligand ï¬eld splitting in [FeCl6]4â and state the relationship that you have used. Is this relationship analytical or empirical? [4 marks]
(e) For the following geometries, sketch stereochemically accurate structures for the isomers (i)â(iii).
(i) facâMX3Y3
(ii) merâMX3Y3
(iii) MXY5
Which selection rules will apply for the d-d transitions of the electrons associated with the metal M? You can assume that âS = 0 applies to M in each case.