(A) The compound [CoCl(en)₂(NO₂)₂] has been prepared in a number of isomeric forms. One form undergoes no reaction with either AgNO₃ or en and is optically inactive. A second form reacts with AgNO₃ to form a white precipitate, does not react readily with en, and is optically inactive. A third form is optically active and reacts both with en and AgNO₃. Assuming a coordination number of 6 for the cobalt ion, identify each of the three isomeric forms by name, and sketch each of the structures.

(B) A compound is analyzed and found to contain 46.2% Pt, 33.6% Cl, 16.6% N, and 3.6% H. The freezing point of a 0.1 M aqueous solution of the compound is –0.74 °C. What is the structural formula of the compound? What possible isomeric forms are there for this compound?