Problem 61 - Chemistry The Molecular Science

Question

Write the name corresponding to cach formula. (a) \(\left[\mathrm{MnCl}_{4}\right]^{2-}\) (b) \(\mathrm{K}_{3}\left[\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]\) (c) \(\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{2}(\mathrm{CN})_{2}\right]\)

Step-by-Step Solution

Answer

(a) Tetrachloromanganate(II) ion; (b) Potassium trisoxalatoferrate(III); (c) Diamminedicyanoplatinum(II).

Step 1: Identify Complex Names

The given chemical formulas are complex ions, each with a transition metal at its center. The task here is to identify the proper name for the complex ions by considering the ligands, oxidation states, and formulas provided.

Step 2: Naming Anionic Complex \\(\mathrm{MnCl}_{4}\, \mathrm{Complex}\\)

For \([\mathrm{MnCl}_{4}]^{2-}\):- 'Cl' stands for chloride, which is the ligand.- 'Mn' represents Manganese, the central metal ion.- Manganese here has an oxidation state of +2 (since chloride is -1 each and there are four of them contributing -4 in total, balancing the -2 charge overall).- Since it is an anionic complex, we use the name 'manganate' for manganese.- Name: Tetrachloromanganate(II) ion.

Step 3: Naming Potassium Ferrioxalate Complex \\(\mathrm{K}_{3}[\mathrm{Fe}(\mathrm{C}_{2}\mathrm{O}_{4})_{3}]\\)

For \(\mathrm{K}_{3}[\mathrm{Fe}(\mathrm{C}_{2}\mathrm{O}_{4})_{3}]\):- 'C_2O_4' is oxalate, a bidentate ligand.- 'Fe' is iron, the central metal ion.- Each oxalate carries a -2 charge, and there are three of them, resulting in a -6 charge.- With three potassium ions (each +1), the total charge on the complex ion must be -3, making the iron have an oxidation state of +3.- Name: Potassium trisoxalatoferrate(III).

Step 4: Naming Neutral Platinum Complex \\(\mathrm{[Pt}(\mathrm{NH}_{3})_{2}(\mathrm{CN})_{2}]\\)

For \([\mathrm{Pt}(\mathrm{NH}_3)_2(\mathrm{CN})_2]\):- 'NH_3' is ammine, a neutral ligand.- 'CN' is cyano, a negative ligand with a -1 charge.- 'Pt' represents platinum, the central metal atom.- The compound is neutral, so the oxidation state of platinum is determined by the balance of cyano's charges with the neutral ammine. Thus, Pt is in its +2 oxidation state.- Name: Diamminedicyanoplatinum(II).

Key Concepts

Complex Ions

In coordination chemistry, complex ions are fascinating structures formed when a central metal ion binds to surrounding molecules or ions known as ligands. These complexes can be either positively charged, negatively charged, or neutral. The bonding between the metal and the ligands involves the donation of electron pairs from the ligands to the central metal ion. Understanding the nature of these interactions is key to mastering coordination chemistry. Complex ions are significant in many biological, industrial, and environmental processes. Let's consider an example with the formula \([MnCl_{4}]^{2-}\). Here, manganese (Mn) is surrounded by four chloride ions (Cl), forming a negatively charged complex. The four chlorides coordinate with the manganese, donating electron pairs to the metal.

Ligand Naming

Ligands are the molecules or ions that are directly attached to the central metal in a complex. Naming these ligands correctly is essential for accurately describing the complex. Ligands can be categorized based on their charge or the number of donor atoms. - **Neutral Ligands:** These do not carry a charge. For instance, ammonia (\(NH_3\)) is called 'ammine'.- **Anionic Ligands:** These carry a negative charge. Chloride (\(Cl^-\)), as seen in \([MnCl_{4}]^{2-}\), is called 'chloro'. Oxalate (\(C_2O_4^{2-}\)) is another example, called 'oxalato'.When naming the complex, the ligands are listed in alphabetical order, followed by the name of the central metal. For example, in \([Pt(NH_3)_2(CN)_2]\), 'ammine' and 'cyano' are named before 'platinum' because of alphabetical precedence.

Oxidation States

Determining the oxidation state of the central metal in a complex is vital for naming and understanding the complex's chemistry. The oxidation state provides insight into how many electrons have been lost or gained by the metal compared to its atomic state. - **For Anionic Complexes:** In \([MnCl_{4}]^{2-}\), chloride is \(-1\) per ligand. With four chlorides, they total \(-4\). The entire complex has a charge of \(-2\), indicating that manganese must be in a \(+2\) oxidation state (\(+2\) to balance the \(-4\) from the chlorides and \(-2\) overall charge).- **For Neutral Complexes:** In \([Pt(NH_3)_2(CN)_2]\), cyano (\(CN^-\)) is \(-1\), while ammine is neutral. Two cyano ions total \(-2\), requiring platinum to be in the \(+2\) state to maintain neutrality.- **Cationic States** are less straightforward but follow similar logic by balancing the total charges of the ligands and overall ion.Understanding these rules helps in determining the correct names and properties of various complex ions.