This question is worth 5 marks, answer all parts.

Consider the complex [CoBr(en)₂(OH₂)]²⁺.

a. Drawn below are all the possible isomers for [CoBr(en)₂(OH₂)]²⁺. Identify how isomers A–E are linked by describing the type of isomerism. (4 marks)

b. In an octahedral complex, explain why an electron in the d_x2-y2 or d_z2 orbital is of higher energy than one in a d_xy, d_xz or d_yz orbital. (1 mark)