Formation of which complex, among the following, is not a confirmatory test of Pb$$^{2+}$$ ions

Identify which compound's formation is NOT a confirmatory test for Pb$$^{2+}$$ ions.

In qualitative inorganic analysis, the standard confirmatory tests for Pb$$^{2+}$$ involve forming characteristic precipitates:

(i) Lead sulphate (PbSO$$_4$$): White precipitate formed by adding dilute H$$_2$$SO$$_4$$. This is a confirmatory test. ✓

(ii) Lead chromate (PbCrO$$_4$$): Yellow precipitate formed by adding potassium chromate (K$$_2$$CrO$$_4$$). This is a well-known confirmatory test. ✓

(iii) Lead iodide (PbI$$_2$$): Yellow precipitate formed by adding KI. On heating, it dissolves and recrystallises as golden-yellow flakes on cooling ("golden rain" test). This is a confirmatory test. ✓

(iv) Lead nitrate (Pb(NO$$_3$$)$$_2$$): Lead nitrate is a water-soluble salt. It does not form a precipitate and is not produced as a result of any confirmatory reaction. In fact, lead nitrate solution is often the starting material used to test for other ions. Its formation is NOT a confirmatory test for Pb$$^{2+}$$.

Therefore, lead nitrate (Option B) is the compound whose formation is not a confirmatory test for Pb$$^{2+}$$ ions.