Step 1: Defining Coordination Compounds.
Coordination compounds are molecules or ions featuring a central metal atom or ion bonded to surrounding ligands. These compounds find significant applications in fields such as medicine, industry, and biological systems.
Step 2: Evaluating the Options.
- Option 1: cis-platin effectively inhibits tumour growth. This is a recognized application of a coordination compound, with platinum complexes utilized in chemotherapy.
- Option 2: Chlorophyll facilitates photosynthesis. While chlorophyll is essential for photosynthesis, it is not classified as a typical coordination compound. It is a complex, but its function differs from the specific roles of coordination compounds.
- Option 3: Desferrioxime B treats lead poisoning. This is a valid application of a coordination compound, employed in chelation therapy for lead poisoning.
- Option 4: Cyanocobalamin, an antipernicious anemia factor, is a cobalt coordination compound. Cyanocobalamin is a form of vitamin B₁₂, a coordination compound containing cobalt, used to treat pernicious anemia.
Step 3: Determination.
The sole incorrect application of a coordination compound among the options is (2), as chlorophyll's role in photosynthesis does not align with the definition of a coordination compound.
Final Answer: \[\boxed{\text{The correct answer is (2) chlorophyll helps in photosynthesis.}}\]