Magnetic Susceptibility of Coordination Compounds in the General Chemistry Laboratory

摘要

A general chemistry laboratory exercise is described in which the number of unpaired electrons in coordination compounds is determined. The compounds are Na₂PdCl₄, K₄Fe(CN)₆, Cr(acac)₃, Na₃FeF₆, Co(acac)₃ and Mn(acac)₂. These compounds are presented to students as Na₂PdA₄, K₄FeA₆, CrB₃, Na₃FeA₆, CoB₃ and MnB₂ respectively where A is monodentate, B is bidentate and both ligands have a charge of ?1. For a coordination number of six an octahedral structure is assumed, and for a coordination number of four, tetrahedral and square planar structures are assumed. After determining the number of d-level electrons, students select applicable energy level diagrams and assign electrons in all possible arrangements consistent with Hund’s rule. Students cross out inappropriate diagrams, providing an explanation for why they have done so. By comparing the number of unpaired electrons determined using magnetic susceptibility and with the remaining diagrams, students deduce the structure and spin arrangement(s) that fit the experimental results. In about half of the cases, the structure is conclusively determined.