The easiest way would be like this:

(\begin{pmatrix} \boxed{\begin{array}{cc}a* & b*\\ d* & e*\end{array}}&\begin{array}{c}c \\ f\end{array} \end{pmatrix}).

If you don't like the spacing in that, then you can refine it by using an array instead of a pmatrix:

(\left(\begin{array}{c@{\hspace{1pt}}c@{}} \boxed{\begin{array}{cc}a* & b*\\ d* & e*\end{array}}&\begin{array}{c}c \\ f\end{array} \end{array}\right)).