Based on the molar conductance values listed here for the...

Based on the molar conductance values listed here for the series of platinum(IV) complexes, write the formula for each complex so as to show which ligands are in the coordination sphere of the metal. By way of example, the molar conductances of $0.050 \mathrm{M} \mathrm{NaCl}$ and $\mathrm{BaCl}_{2}$ are $107 \mathrm{ohm}^{-1}$ and $197 \mathrm{ohm}^{-1}$, respectively. ${ }^{*}$ The ohm is a unit of resistance; conductance is the inverse of resistance.

Based on the molar conductance values listed here for the series of platinum(IV) complexes, write the formula for each complex so as to show which ligands are in the coordination sphere of the metal. By way of example, the molar conductances of $0.050 \mathrm{M} \mathrm{NaCl}$ and $\mathrm{BaCl}_{2}$ are $107 \mathrm{ohm}^{-1}$ and $197 \mathrm{ohm}^{-1}$, respectively.
${ }^{*}$ The ohm is a unit of resistance; conductance is the inverse of resistance.

Key Concepts

Molar Conductance

Molar conductance is a measure of how well an electrolyte conducts electricity in solution, and it depends on both the number and mobility of ions produced upon dissolution. In the context of coordination complexes, comparing molar conductance values can indicate the number of free (uncoordinated) ions present in solution, thereby helping to deduce which ligands are part of the inner coordination sphere and which serve as counter ions.

Coordination Sphere versus Counter Ions

In coordination chemistry, the coordination sphere refers to the collection of ligands that are directly bonded to the central metal ion, while counter ions exist outside this sphere to balance the overall charge. By analyzing properties such as molar conductance, one can determine the extent to which ionization occurs; a low molar conductance suggests fewer free ions, implying that more ligands are bound within the coordination sphere rather than being free counter ions.

Electrolyte Behavior in Complexes

Electrolyte behavior in coordination compounds is linked to the degree of ionization when the compound dissolves in a solvent. Complexes that release several ions into solution exhibit higher electrical conductivity, whereas complexes that remain largely intact with ligands held in the coordination sphere show lower conductivity. This behavior is crucial for deducing the formula and the arrangement of ligands in a metal complex.

Complex Ion Structural Formulations

Understanding the structure of complex ions involves differentiating between the coordinated ligands directly bonded to the metal and the external ions present to balance the charged complex. By knowing the molar conductance and the extent of dissociation, chemists can construct the appropriate formula for a coordination compound that clearly separates the coordination sphere (inside brackets) from the counter ions.

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