Question

3. According to the textbook (p. 115). the electron transfer reaction rate between [Co(NH3)]** and (Co(NH3).]?(eq. 5.41) is extremely slow whereas that between [Fe(CN).74 and [Fe(CN).]" (eq. 5.42) is very fast. By using the established facts in the box in answering the following questions. 1. According to the molecular orbital theory, the eg orbitals of an MLO octahedral complex are, in fact, M-L anti-bonding orbitals and the tza orbitals are non-bonding orbitals. 2. According to the spectrochemical series, CN is a very strong field ligand. H2O is a typical weak field ligand, and NH, is an intermediate field ligand. (1) Rationalize the four M-L bond distances in eqs. 5.41 and 5.42. That is why is the Fe-CN bond distance unchanged with the oxidation state of Fe while the Co-NH3 bond distance changes significantly with the oxidation state of Co. (2) Predict the reaction rate for the case when all the NHg ligands in eq. 5.41 are replaced by H,O. Will this reaction be faster or slower than the reaction in eq. 5.41? (3) Predict the reaction rate for the case when all the CN ligands in eq. 5.42 are replaced by H,0. Will this reaction be faster or slower than the reaction in eq. 5.42? -> [CO(NH), )** + [CO(NH3)6]3+ ka 10-6 Mist * eq 5.41 = [Co (NH)6] ** + [CO(NH3),] Colt - NHS Coat - NH3 = 1.94 = 2.11 eg5.42 → [Fe(CN)6]4- + [Fe(CN).] Fe2+ - CN Fest - CN 21.92 Å = 1.95 Å → [Fe(CN), ] + [Fe(CN).]4- K = 700 Mist

Answer 1

* et 5 || → [Co (NH4) ] + [Cu(NH4)3+ =[Cu(NH3),3* +[Co ( NH ) Colt - NH3 Colt - NH3 = 1.94 Å ka 10-6 Mist = 2.11 Å €85.42 => [Fe(CN)6]4- + [Fe(CN).]--> [Fe(CN),] + [Fe(CN).]*- Feat - CN Fest- CN 21.92 >> 1.95 Å K = 700 Mist