The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《trans-Dichlorotetrakis(pyridine)platinum(IV) nitrate: a classical coordination compound》. Authors are Seddon, Kenneth R.; Turp, Janet E.; Constable, Edwin C.; Wernberg, Ole.The article about the compound:cis-Dichlorobis(pyridine)platinum(II)cas:15227-42-6,SMILESS:[Cl-][Pt+2]([N]1=CC=CC=C1)([Cl-])[N]2=CC=CC=C2).Application In Synthesis of cis-Dichlorobis(pyridine)platinum(II). Through the article, more information about this compound (cas:15227-42-6) is conveyed.
Claims that trans-[PtCl2(py)4](NO3)2 forms a covalent hydrate when dissolved in water are shown to be in error; the observed acidity of the aqueous solution is due to the presence of a small amount of a strongly acidic impurity, and all of the observed phys. and spectroscopic properties of the salt are simply interpreted in terms of classical coordination chem.
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Reference:
Tetrahydroisoquinoline – Wikipedia,
1,2,3,4-Tetrahydroisoquinoline | C9H11N – PubChem