Q4. Indicate the types of isomerism shown by (i) K[Cr(H2O)2(C2O4)2], (ii) [Co(en)3]Cl3, (iii) [Pt(NH3)(H2O)Cl2]. (NCERT Intext Question 5.3, parts (i), (ii) and (iv).)
(i) Geometrical (cis and trans), and the cis form is optically active, so three stereoisomers in all. (ii) Two optical isomers. (iii) Geometrical, cis and trans (NCERT answers, page 140). NCERT prints part (i) without its closing bracket.
Q5. How many geometrical isomers are possible for (i) [Cr(C2O4)3]3− and (ii) [Co(NH3)3Cl3]? (NCERT Exercise 5.9.)
(i) None: three identical didentate ligands can be arranged in only one geometrical way, although that arrangement is chiral, so the ion has two optical isomers. (ii) Two, fac and mer, as for [Co(NH3)3(NO2)3] (NCERT page 126) (reasoned).
Q6. How many stereoisomers do (i) [Co(NH3)Cl(en)2]2+ and (ii) [Co(NH3)2Cl2(en)]+ have? (Based on NCERT Exercises 5.10 and 5.11.)
(i) Three: NH3 and Cl trans to each other (not chiral), or cis, which exists as a d and an l form. (ii) Four: the two NH3 trans to each other, the two Cl trans to each other (neither chiral), or all four cis, which exists as a d and an l form (reasoned).
Q7. How many geometrical isomers does the square planar [Pt(NH3)(Br)(Cl)(py)] have, and how many of them are optically active? (NCERT Exercise 5.12.)
Three, fixed by which ligand is trans to NH3: Br, Cl or py, the [MABXL] case on NCERT page 125. None is optically active, because the plane of the complex is a mirror plane (reasoned).