Q.Draw geometric isomers and enantiomers of the following complexes.

Step 1. (a) [Pt(en)3]4+. A homoleptic tris-chelate octahedral complex (three identical bidentate en ligands), directly analogous to [Co(en)3]3+ (section 9.7.1). No geometric (cis/trans) isomerism is possible, since all three ligands are identical bidentate units with only one way to arrange them; but the complex IS chiral (the three chelate rings' shared 'twist' has no internal mirror plane), existing as a d/l enantiomer pair.

Step 2. (b) [Pt(en)2ClBr]2+. An M(AA)2BC-type octahedral complex (2 bidentate en, one Cl, one Br) -- the exact pattern the book works through for [PtCl2(en)2]2+ (Fig. 9.7.1-f). It shows both cis and trans geometric isomers; and, matching that worked pattern, only the CIS isomer is further chiral, existing as its own d/l enantiomer pair, while the trans isomer has a mirror plane and is achiral.

Step 3. (c) [CoCl3(NH3)3]. An MA3B3-type octahedral complex (3 Cl, 3 NH3). This ligand pattern does not give simple cis/trans isomers; instead it gives facial (fac) and meridional (mer) isomers -- in fac, the three identical Cl ligands occupy one triangular face of the octahedron (all mutually cis, 90 degrees apart); in mer, the three Cl ligands lie along one meridian (a plane through the centre), with two of them trans to each other. Both fac and mer forms of a symmetric MA3B3 octahedral complex possess an internal mirror plane and are achiral -- no enantiomers exist for either. …

Classifying each complex by its ligand pattern (homoleptic tris-chelate / M(AA)2BC / MA3B3 / homoleptic MA-only) and applying the matching isomerism rules from section 9.7.1, e …

• Applying simple cis/trans terminology to the MA3B3 complex in (c), instead of the correct fac/mer distinction. …