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Ch.21 - Transition Elements and Coordination Chemistry
All textbooksMcMurry 8th EditionCh.21 - Transition Elements and Coordination ChemistryProblem 124
Chapter 21, Problem 124

The drug Nipride, Na2[Fe(CN)5NO], is an inorganic complex used as a source of NO to lower blood pressure during surgery. (a) The nitrosyl ligand in this complex is believed to be NO+ rather than neutral NO. What is the oxidation state of iron, and what is the systematic name for Na2[Fe(CN)5NO]? (b) Draw a crystal field energy-level diagram for [Fe(CN)5NO]2-, assign the electrons to orbitals, and predict the number of unpaired electrons.

Verified step by step guidance
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Step 1: Determine the oxidation state of iron in Na2[Fe(CN)5NO]. Start by assigning oxidation states to the known components: Na is +1, CN is -1, and NO is +1 (as NO+). The overall charge of the complex ion [Fe(CN)5NO]2- is -2. Set up an equation to solve for the oxidation state of Fe.
Step 2: Solve the equation for the oxidation state of Fe. The equation is: 2(+1) + x + 5(-1) + (+1) = -2, where x is the oxidation state of Fe. Simplify and solve for x.
Step 3: Write the systematic name for Na2[Fe(CN)5NO]. Use the oxidation state of iron determined in Step 2 and the names of the ligands to construct the name. Remember that CN is called 'cyano' and NO+ is called 'nitrosyl'.
Step 4: Draw the crystal field energy-level diagram for [Fe(CN)5NO]2-. Consider the strong field ligands (CN and NO+) and their effect on the splitting of the d-orbitals. Arrange the d-orbitals according to the crystal field theory for a low-spin complex.
Step 5: Assign the electrons to the orbitals in the crystal field diagram. Use the electron configuration of Fe and the oxidation state determined earlier to find the number of d-electrons. Distribute these electrons in the energy-level diagram and count the number of unpaired electrons.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Oxidation State

The oxidation state of an element in a compound indicates the degree of oxidation of that element, reflecting the number of electrons lost or gained. In coordination complexes, the oxidation state can be determined by considering the charges of the ligands and the overall charge of the complex. For example, in Na2[Fe(CN)5NO], the nitrosyl ligand is treated as NO+, which influences the calculation of iron's oxidation state.
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Oxidation Numbers

Coordination Complex Nomenclature

The systematic naming of coordination complexes follows specific rules, including identifying the central metal, the oxidation state, and the ligands. In the case of Na2[Fe(CN)5NO], the name reflects the metal (iron), the ligands (cyanide and nitrosyl), and the overall charge. Understanding these conventions is essential for accurately naming and interpreting the structure of coordination compounds.
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Coordination Complexes Example

Crystal Field Theory

Crystal Field Theory (CFT) explains the electronic structure of transition metal complexes by considering the effect of ligands on the d-orbitals of the metal ion. Ligands create an electrostatic field that splits the degenerate d-orbitals into different energy levels. This theory helps predict the number of unpaired electrons and the magnetic properties of the complex, which are crucial for understanding its behavior in various chemical contexts.
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The study of ligand-metal interactions helped to form Ligand Field Theory which combines CFT with MO Theory.
Related Practice
Textbook Question

For each of the following, (i) give the systematic name of the compound and specify the oxidation state of the transition metal, (ii) draw a crystal field energy-level diagram and assign the d electrons to orbitals, (iii) indicate whether the complex is high-spin or low-spin (for d4 - d7 complexes), and (iv) specify the number of unpaired electrons. (d) K4[Os(CN)6]

Textbook Question

For each of the following, (i) give the systematic name of the compound and specify the oxidation state of the transition metal, (ii) draw a crystal field energy-level diagram and assign the d electrons to orbitals, (iii) indicate whether the complex is high-spin or low-spin (for d4 - d7 complexes), and (iv) specify the number of unpaired electrons.

(e) [Pt(NH3)4](ClO4)2

Textbook Question

For each of the following, (i) give the systematic name of the compound and specify the oxidation state of the transition metal, (ii) draw a crystal field energy-level diagram and assign the d electrons to orbitals, (iii) indicate whether the complex is high-spin or low-spin (for d4 - d7 complexes), and (iv) specify the number of unpaired electrons.

(f) Na2[Fe(CO)4]

Textbook Question

Give a valence bond description of the bonding in each of the following complexes. Include orbital diagrams for the free metal ion and the metal ion in the complex. Indicate which hybrid orbitals the metal ion uses for bonding, and specify the number of unpaired electrons.

(a) [Ti(H2O)6]3+

Textbook Question

Give a valence bond description of the bonding in each of the following complexes. Include orbital diagrams for the free metal ion and the metal ion in the complex. Indicate which hybrid orbitals the metal ion uses for bonding, and specify the number of unpaired electrons.

(c) [Fe(CN)6]3- (low-spin)