Isomerism is traditionally introduced in organic chemistry courses. However, inorganic chemistry als — Organic Chemistry Chemistry Question
Isomerism in Inorganic Chemistry
Isomerism is traditionally introduced in organic chemistry courses. However, inorganic chemistry also offers many different types of isomerism, especially structural. The modern study of coordination compounds began with Alfred Werner 1) and Sophus Mads Jorgensen, more than one hundred years ago. It was their experiments that established the octahedron as the premier structural entity for coordination number six (6) rather than the planar hexagon or the trigonal prism, for example in the complex ion Co(NH3)6 3+. Thus, there are two isomers corresponding to the chemical formula CoCl3×4 NH3 , the praseo and violeo complexes. There are also two structural isomers for the complex Rh(py)3Cl3 (py: pyridine – only its N–atom needs to be considered). The far infrared spectra in the 450–200 cm–1 region of these two complexes are shown in the figure below.
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Rotation of plane polarized light is not limited to organic molecules with a chiral carbon atom. The general condition for optical activity is that the molecule or ion should not possess an improper axis of rotation, and because S2 ≡ i and S1 ≡ σ the molecule may not possess a center or plane of symmetry. Thus, although there is only one cis–[Co(NH3)4Cl2]Cl complex, there are two cis–[Co(en)2Cl2]Cl complexes (en: ethylene diamine or 1,2 diamino ethane, a symmetric bidentate ligand) which are enantiomers.
- Nobel prize in Chemistry 1913
What is the electronic configuration of Co in Co(NH3)6 3+ ?
Model Answer
27Co [1s2 2s2 2p6 3s2 3p6] 3d7 4s2
Co3+ [Ar] 3d6
What is the type of bonding of NH3 in Co(NH3)6 3+ , which is a low spin complex, and of fluoride ion in CoF6 3– , which is a high spin complex? Place electrons from the ligands in appropriate metal orbitals according to Valence Bond Theory.
Model Answer
Dative covalent by the ligand into an empty metal orbital. d2sp3 hybridization.
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Outer sphere paramagnetic complex.
Write the stereochemical formulae and structures for the praseo and violeo complexes.
Model Answer
trans
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cis
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Write the stereochemical formulae and structures for the two Rh(py)3Cl3 complexes. Assign the spectra to each of the two complexes.
Model Answer
fac
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mer
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Spectrum A corresponds to the fac isomer (higher symmetry, fewer bands), and Spectrum B corresponds to the mer isomer (lower symmetry, more bands).
How many isomers does the complex with the formula [Co(en)3]I3 exibit ?
Model Answer
2 enantiomers ± Co(en)3 3+
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