I donated some money to a charitable project out of embarrassment and fear of my boss,
but if I had had the choice, I would not have donated a penny. Will I be fully rewarded for this deed just as if I have done it out of free will? Please, clarify this point and cite the evidence.
If the case is as you mentioned, then you will not be rewarded for donating this sum, as it was not in the Cause of Allah, but out of fear of your boss. It is authentically reported that the Prophet (peace be upon him) said:
Actions are only according to intentions, and every person shall have but that which he intended...
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and companions.