Mark Zuckerberg will likely pocket about $1 billion from his first stock sale since Facebook Inc.'s initial public offering, part of a complex transaction in which the founder and chief executive also plans to donate stock valued at roughly $1 billion to charity.

Facebook itself will also raise roughly $1.5 billion by selling 27 million additional shares, intended to meet demands from investors after the social network joins the S&P 500 index after Friday's trading. Many index funds that would typically buy Facebook on...