Alex wrote:
An investor will be investing 2,500 in year 1,
not taking any return for 5 years, but at the
end of year 6 wants a payment so that his IRR
upon receiving that payment will equal 25%.

If I understand you correctly, you simply want
the future value (FV) a 6-year investment of
$2500 at 25% per year.

=FV(25%,6,,-2500)