Question

Name the following complex ions. a. \(\mathrm{Ru}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}^{2+}\) b. \(\mathrm{Fe}(\mathrm{CN})_{6}{ }^{4-}\) c. \(\mathrm{Mn}\left(\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\right)_{3}{ }^{2+}\) d. \(\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{NO}_{2}{ }^{2+}\) e. \(\mathrm{Ni}(\mathrm{CN})_{4}{ }^{2-}\) f. \(\mathrm{Cr}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}^{+}\) g. \(\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}{ }^{3-}\) h. \(\mathrm{Co}(\mathrm{SCN})_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}^{+}\)

Short answer

a. pentaamminechloridoruthenium(II) b. hexacyanoferrate(II) c. tris(ethylenediamine)manganese(II) d. pentaamminenitrito-N-cobalt(III) e. tetracyanonickelate(II) f. tetraamminedichlorochromium(III) g. trioxalatoferrate(III) h. diamminetetrakis(thiocyanato-N)cobalt(II)

Step-by-step solution

a. Ru(NH3)5 Cl^2+

This complex ion has a central ruthenium (Ru) atom, five ammonia (NH3) ligands, and one chloride (Cl) ligand with a 2+ charge overall. Therefore, the name is pentaamminechloridoruthenium(II).

b. Fe(CN)6^4-

This complex ion has a central iron (Fe) atom, six cyanide (CN) ligands, and an overall charge of 4-. Therefore, the name is hexacyanoferrate(II).

c. Mn(NH2CH2CH2NH2)3^2+

This complex ion has a central manganese (Mn) atom and three ethylenediamine (NH2CH2CH2NH2) ligands with a 2+ charge overall. Therefore, the name is tris(ethylenediamine)manganese(II).

d. Co(NH3)5 NO2^2+

This complex ion has a central cobalt (Co) atom, five ammonia (NH3) ligands, and one nitrito-N (NO2) ligand with a +2 charge. Therefore, the name is pentaamminenitrito-N-cobalt(III).

e. Ni(CN)4^2-

This complex ion has a central nickel (Ni) atom and four cyanide (CN) ligands with an overall charge of 2-. Therefore, the name is tetracyanonickelate(II).

f. Cr(NH3)4 Cl2^+

This complex ion has a central chromium (Cr) atom, four ammonia (NH3) ligands, and two chloride (Cl) ligands with a +1 charge. Therefore, the name is tetraamminedichlorochromium(III).

g. Fe(C2O4)3^3-

This complex ion has a central iron (Fe) atom and three oxalate (C2O4) ligands with an overall charge of 3-. Therefore, the name is trioxalatoferrate(III).

h. Co(SCN)2(H2O)4^+

This complex ion has a central cobalt (Co) atom, two thiocyanato-N (SCN) ligands, and four aqua (H2O) ligands with a +1 charge. Therefore, the name is diamminetetrakis(thiocyanato-N)cobalt(II).

Key concepts

Naming Coordination Compounds

When naming coordination compounds, it is important to follow a specific set of rules to clearly describe the composition and charge of the complex ion involved. The process typically begins by identifying the ligands attached to the central metal atom. These are named before the metal itself.

• If multiple ligands of the same type are present, prefixes such as 'di-', 'tri-', 'tetra-', 'penta-', and 'hexa-' are used to denote their number.
• The ligands themselves are named in alphabetical order, regardless of their number. The name of the central metal comes after the ligands.
• For anionic complexes, the metal's name ends in the suffix '-ate'. Additionally, the oxidation state of the metal is written in Roman numerals within parentheses immediately following the metal's name.
• If the complex ion is an overall cation, the name of the metal doesn’t change.

These rules help ensure clarity, particularly for chemists studying the properties and reactions of these compounds in coordination chemistry.

Ligands

Ligands are crucial components of coordination compounds. They are ions or molecules that donate a pair of electrons to the central metal atom or ion, forming a coordinate covalent bond. This interaction plays a significant role in the functionality and stability of coordination complexes.

• Ligands can be neutral molecules like water ( H_2O), ammonia ( NH_3), or ions such as chloride ( Cl^-) and cyanide ( CN^-).
• The number of donor atoms a ligand has is referred to as its 'dentate' nature. For instance, ethylenediamine ( NH_2CH_2CH_2NH_2) is a bidentate ligand, meaning it can attach to the metal at two points.
• Ligands determine the geometrical structure of the complex and influence the electronic properties of the metal center, affecting its reactivity and color.

Understanding ligands is essential for mastering the principles of coordination chemistry.

Transition Metals

Transition metals are often at the center of coordination compounds. These elements are found in the d-block of the periodic table and include metals like iron ( Fe), manganese ( Mn), ruthenium ( Ru), and cobalt ( Co). They possess unique properties that make them ideal for forming coordination complexes:

• Transition metals can exhibit multiple oxidation states, allowing them to form a variety of compounds with different charges and ligands.
• They have partially filled d-orbitals, enabling them to form stable complexes with ligands by accepting electron pairs via coordinate covalent bonds.
• The ability to form colored compounds due to d-d electron transitions gives transition metal complexes distinct and varied colors.

These properties make transition metals highly significant in both industrial applications and biological systems, playing essential roles in processes such as catalysis and electron transport.

Coordination Chemistry

Coordination chemistry is a fascinating field that encompasses the study of complex compounds formed by transition metals and their ligands. It focuses on understanding how metals interact with ligands and the resulting implications on the properties and behavior of the compounds formed.

• Coordination compounds are vital in numerous applications, including medicinal chemistry, where they are used in drugs and as imaging agents in MRI scans.
• Inhomogeneous catalysis, coordination complexes created with specific ligands enhance the reactivity and selectivity of transition metals.
• The electronic properties of transition metals, modified by their ligands, play a crucial role in processes such as photosynthesis and respiration in biological systems.

Studying coordination chemistry provides insights into the molecular architecture and reactivity of these compounds, contributing to advancements in chemistry and related sciences.