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Question: structure of Na₄[Fe(CN)₅NOS]...

structure of Na₄[Fe(CN)₅NOS]

Answer

The structure of Na₄[Fe(CN)₅NOS] consists of four sodium cations (Na⁺) and an octahedral complex anion [Fe(CN)₅NOS]⁴⁻. The central iron atom is in the +2 oxidation state (Fe(II)). It is coordinated to five cyanide (CN⁻) ligands and one sulfidonitrosyl (NOS⁻) ligand. The NOS⁻ ligand binds to the iron through its nitrogen atom, which is also bonded to sulfur and oxygen.

Explanation

Solution

The compound Na₄[Fe(CN)₅NOS] is a coordination complex.

  1. Complex Ion and Counter Ions: The compound consists of four sodium ions (Na⁺) as counter ions and a complex anion, [Fe(CN)₅NOS]⁴⁻.

  2. Central Metal Atom: The central metal atom is Iron (Fe).

  3. Ligands:

    • Five cyanide ligands (CN⁻). Each CN⁻ ligand has a charge of -1.
    • One "NOS" ligand. This ligand is formed when the nitroprusside ion, [Fe(CN)₅NO]²⁻, reacts with a sulfide ion (S²⁻). In nitroprusside, the NO ligand is often considered as NO⁺ for charge balance (leading to Fe(II)). When S²⁻ attacks the electrophilic nitrogen of the NO⁺ ligand, it forms the NOS⁻ ligand (NO⁺ + S²⁻ → NOS⁻). Thus, the NOS ligand has a charge of -1.

  4. Oxidation State of Iron: Let the oxidation state of Fe be 'x'. The total charge of the complex ion is -4. x + 5(charge of CN⁻) + 1(charge of NOS⁻) = -4 x + 5(-1) + 1(-1) = -4 x - 5 - 1 = -4 x - 6 = -4 x = +2 So, the oxidation state of Iron is +2, i.e., Fe(II).

  5. Coordination Number and Geometry: The central Fe(II) ion is coordinated to six ligands (five CN⁻ and one NOS⁻). Therefore, the coordination number is 6, and the complex adopts an octahedral geometry.

  6. Structure of the NOS Ligand: The NOS⁻ ligand, also known as sulfidonitrosyl or thionitrosyl, is bonded to the Fe(II) ion through its nitrogen atom. The nitrogen atom is also bonded to the sulfur and oxygen atoms. The structure can be represented as Fe-N(S)O.

Summary of Structure:

Na₄[Fe(CN)₅NOS] is composed of four Na⁺ ions and an octahedral complex anion [Fe(CN)₅NOS]⁴⁻. The central metal ion is Fe(II), coordinated to five cyanide (CN⁻) ligands and one sulfidonitrosyl (NOS⁻) ligand. The NOS⁻ ligand bonds to Fe through its nitrogen atom, which is also bonded to sulfur and oxygen.