How is this compound to be named?

Please show the calculation for the oxidation number

[Pt(NH3)2Cl(NH2CH3)]Cl

Ans is: Diamminechloromethylammineplatinum(II) chloride

First, find out the oxidation state of the metal platinum.
Counter ion is Cl which always have -1 charge.
Since, there is only one Cl- ion, thus coordination sphere i.e. [Pt(NH3)2Cl(NH2CH​3)] will have +1 charge to make the coordination compound neutral.

Now to calculate the oxidation number of metal from the coordination sphere cation, write the charge on each ligand and the metal inside coordination sphere and equate it to total charge on cation.
Let us take oxidation number of Pt to be 'x'. NH3 and NH2CH3 are neutral, so they will have 0 charge. Cl has -1 charge.
Thus, x + 0 - 1 + 0 = +1
 x = + 1 + 1 = +2
Thus Pt will have +2 oxidation state.

Now. to write the name of the compound, first name the coordination sphere, as cation is always named first. For this, name all the ligands and then see their first alphabet.
(NH3)2 is diammine ('di' shows there are two ammine groups. Hence it will not be considered while seeing alphabetical order. Consider 'a' of ammine)
(NH2CH3) is methylammine
Cl is chloro

Now arrange the ligands in increasing order of their starting first alphabet (shown above in bold) followed by metal with its oxidation state in brackets. This should be written without any space in between each letter. Then write the name of anion which is chloride (Cl-).
[NOTE: Cl inside coordination sphere is acting as a ligand. Hence it will be named as chloro. While the anion will be ended with suffix 'ide' instead of 'o'. Hence anion Cl- will be chloride]

Thus, the name of the compound will be

Diamminechloromethylammineplatinum(II) chloride

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