In 1956, Dorothy Crowfoot Hodgkin discovered the structure of Vitamin B12 or its other name 'Cobalamin' because it has a transition metal, cobalt, as the central atom surrounded by complex amine groups and other complex functional groups as multidentate ligands.Based on the structure of Cobalamin, presented below in the picture, what could be the coordination number?
Correct answer: D. 6
- A. 3
- B. 4
- C. 5
- D. 6
Explanation
The structure of Vitamin B12, as described in the information, consists of cobalt as the central atom surrounded by six ligands: a tetradentate corrin ring system, a 5-deoxyadenose ligand on top, and a dimethyl benzimidazole ligand below. This arrangement of six ligands around the central cobalt atom forms an octahedral shape, and hence, the coordination number is 6.
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Valence shell electron pair repulsion theory predicts molecular shape by arranging bonding pairs and lone pairs around a central atom to minimize repulsion. Questions cover linear, trigonal planar, tetrahedral, trigonal bipyramidal and octahedral electron geometries, bond angles and distortions caused by lone pairs. Electron geometry is not always the same as molecular shape.
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