Chapter 21, Problem 68RQ

The following compound is called diethylenetriamine and is abbreviated “dien”:

$\stackrel{\mathrm{..}}{\text{N}}{\text{H}}_{\text{2}}{\text{—CH}}_{\text{2}}{\text{—CH}}_{\text{2}}\text{—}\stackrel{\mathrm{..}}{\text{N}}{\text{H—CH}}_{\text{2}}{\text{—CH}}_{\text{2}}\text{—}\stackrel{\mathrm{..}}{\text{N}}{\text{H}}_{\text{2}}$

When it bonds to a metal, it is a ligand with three donor atoms.

(a) Which are most likely the donor atoms?

(b) What is the coordination number of cobalt in the complex $\text{Co}{\left(\text{dien}\right)}^{\text{3+}}$?

(c) Sketch the structure of the complex ${\left[\text{Co}{\left(\text{dien}\right)}_{\text{2}}\right]}^{\text{3+}}$.

(d) Which complex would be expected to be more stable in aqueous solution, ${\left[\text{Co}{\left(\text{dien}\right)}_{\text{2}}\right]}^{\text{3+}}\text{or }\left[\text{Co}{\left({\text{NH}}_{\text{3}}\right)}_{\text{6}}\right]{\text{3}}^{\text{+}}$?

(e) What would be the structure of triethylenetetraamine?