Q.$Fe^{2+}$ ions react with nitric oxide formed from reduction of nitrate and yields a brown coloured complex _______.

Vitamin B12 (cyanocobalamin) contains a central cobalt ion in a corrin ring — a biologically important coordination compound.

Several biomolecules are metal complexes:

• Chlorophyll contains magnesium.
• Haemoglobin contains iron. …

Cisplatin, cis-diamminedichloridoplatinum(II), is a widely used platinum-based anticancer coordination complex.

Cisplatin, cis-diamminedichloridoplatinum(II), $cis$-$[PtCl_2(NH_3)_2]$, is a square planar platinum coordination complex used extensively in chemotherapy for the treatment of various cancers (e.g. testicular, ova …

Chlorophyll contains magnesium; the others contain Cu, Zn or Co.

Many biologically important molecules are metal complexes:

• (A) Chlorophyll — contains Mg2+ at the centre of a porphyrin ring; essential for photosynthesis.
• (B) Haemocyanin — a copper(Cu)-containing oxygen carrier in some invertebrates. …

Nessler's reagent, $K_2[HgI_4]$ in KOH, gives a brown precipitate/colouration with ammonia — a classic coordination-complex-based analytical test.

Nessler's reagent is prepared by dissolving mercury(II) chloride and potassium iodide in excess KI (forming the tetraiodomercurate(II) complex ion $[HgI_4]^{2-}$) and making the solution strongly alkaline with KOH. When treated with a trace of ammonia or ammonium salt, it produces a characteristic yellow-to-brown colouration or precipitate (an iodide of Millon's base, $[Hg_2N]I\cdot H_2O$-type spe …

The brown-ring test's coloured species is the nitrosyl complex $[Fe(H_2O)_5NO]^{2+}$.

In the 'brown ring' test for nitrate ion, dilute $NO_3^-$ solution is treated with freshly prepared $FeSO_4$ and then conc. $H_2SO_4$ is added carefully along the side of the tube. The acid reduces nitrate to nitric oxide, $NO_3^- + 3Fe^{2+} + 4H^+ \rightarrow NO + 3Fe^{3+} + 2H_2O$, and the $NO$ formed combines with an unreacted $Fe^{2+}$ ion (which already carries five aqua liga …

Cisplatin, $cis$-$[Pt(NH_3)_2Cl_2]$, is a platinum coordination-compound chemotherapy drug.

Cisplatin, $cis$-diamminedichloridoplatinum(II), $cis$-$[Pt(NH_3)_2Cl_2]$, is a square-planar coordination compound of platinum(II) used as an anticancer (chemotherapy) drug — it works by binding to DNA in cancer cells an …