`Co^(2+)(aq.)+SCN^(-)(aq.)to"Complex"(X)`
`Ni^(2+)(aq.)+"Dimethylglyoxime"overset(NH_4OH)to"Complex"(Y)`.
The coordination number of cobalt and nickel in complexes X and Y is four.
The IUPAC name of the complexes (X) and (Y) are respectively:

Options

A. Tetrathiocyanato-S-cobalt(II) and Bis(dimethylglyoximato) nickel(II)
B. Tetrathiocyanato-S-cobaltate(II) and Bis(dimethylglyoximato) nickel(II)
C. Tetrathiocyanato-S-cobalt(II) and Bis(dimethylglyoximato) nickelate(II)
D. Tetrathiocyanato-S-cobalt(III) and Bis(dimethylglyoximate) nickel(II)

Explanation

To find the IUPAC names of the complexes formed from the reactions of Co²⁺ with SCN⁻ and Ni²⁺ with dimethylglyoxime, we will follow these steps:

### Step 1: Determine the Complex X from Co²⁺ and SCN⁻
1. **Identify the Ligand**: SCN⁻ (thiocyanate) is a monodentate ligand.
2. **Coordination Number**: The coordination number of cobalt in complex X is given as 4.
3. **Complex Formation**: Since there are 4 SCN⁻ ligands, the complex can be represented as [Co(SCN)₄]²⁻.
4. **Oxidation State of Cobalt**: The overall charge of the complex is -2. Since each SCN⁻ contributes -1, the charge from cobalt must be +2 to balance it:
\[ -4 + x = -2 \implies x = +2 \]
5. **Naming the Complex**: According to IUPAC naming conventions:
- Ligands are named before the central metal.
- The ligand is named as "thiocyanato" when it is bonded through sulfur (S).
- Since the complex is anionic, the suffix "-ate" is added to the name of cobalt, making it "cobaltate".
- The oxidation state of cobalt (+2) is indicated in Roman numerals.

Thus, the IUPAC name for complex X is:
**Tetra-thiocyanato-S-cobaltate(II)**

### Step 2: Determine the Complex Y from Ni²⁺ and Dimethylglyoxime
1. **Identify the Ligand**: Dimethylglyoxime (DMG) is a bidentate ligand.
2. **Coordination Number**: The coordination number of nickel in complex Y is also given as 4.
3. **Complex Formation**: Since DMG is bidentate, two DMG ligands will coordinate with nickel, forming [Ni(DMG)₂].
4. **Oxidation State of Nickel**: The complex is neutral, so the oxidation state of nickel must be +2:
\[ +2 + x = 0 \implies x = +2 \]
5. **Naming the Complex**: According to IUPAC naming conventions:
- The ligand is named "dimethylglyoximato" since it is already a part of the ligand name.
- The central metal is named "nickel" without the "-ate" suffix because the complex is neutral.
- The oxidation state of nickel (+2) is indicated in Roman numerals.

Thus, the IUPAC name for complex Y is:
**Bis(dimethylglyoximato)nickel(II)**

### Final Answer
The IUPAC names of the complexes X and Y are:
1. **Complex X**: Tetra-thiocyanato-S-cobaltate(II)
2. **Complex Y**: Bis(dimethylglyoximato)nickel(II)