Need Help with a 555 timer circuit

I am trying to make a 555 timer circuit (monostable) that will stay high for 5 min once the switch has closed. Based on the math, I am using a 470uF electrolytic capacitor and a 590 ohm resistor in order to reach the desired 300 second mark (1.1 x 590,000 x .000470 = 305 sec), however when I tested the circuit, the output always stays high and never drops. I have heard the electrolytic capacitors have a tendancy to leak charge and can affect the overall timing in a 555, so I swapped out the 470uF and replaced it with a 220uF capacitor to see if there was any difference. Although the high time should have been about half, there was no change and the output never dropped low. I have a feeling I am missing something. Can someone please take a look at the attached circuit diagram and let me know where my error is? Thanks!

Your pin 2 is always grounded. Look at these two versions:
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Ken

hi BM,
Look at this option.

Wow, a lot more capacitors than I originally thought. I'll give this a try tonight and see how everything turns out. Thanks, guys!

for long delays suggest using the 7555
as I understand it it is better suited for long delays