* Vista Equity buys 2.3% stake in Reliance unit for $1.5 bln
* Deal follows Facebook, Silver Lake investments in Jio Platforms
* Deals to help Reliance eliminate $21.4 bln debt by year end (Adds brokerage comment, updates stock price)
By Sankalp Phartiyal and Kanishka Singh
NEW DELHI, May 8 (Reuters) - India's Reliance Industries Ltd on Friday announced a $1.5 billion stake sale in digital unit Jio Platforms, a third deal in a little over two weeks that will inject a combined $8 billion in the telecoms-to-energy group to help it pare debt.
Private equity firm Vista Equity Partners is buying a 2.3% stake in Jio Platforms, the unit that houses Reliance's telecoms venture Jio Infocomm, for 113.67 billion rupees ($1.5 billion), Mumbai-headquartered Reliance said in a statement.
The investment gives Jio Platforms an equity value of 4.91 trillion rupees and an enterprise value of 5.16 trillion rupees, said Reliance, which is controlled by billionaire tycoon Mukesh Ambani.
The deal comes after Reliance cut a $5.7 billion deal with Facebook for a 9.99% stake in Jio Platforms on April 22, and just days after it secured a $750 million investment from private equity firm Silver Lake.
The deals, along with its plan to sell $7 billion in new shares, will help Reliance meet its target of eliminating $21.4 billion of net debt by the end of the year.
The negotiations between Reliance and Vista were built off personal connections between the private equity firm's founder Robert Smith and Ambani, a person familiar with the matter said.
The discussions were led by Ambani's close aide Manoj Modi and Brian Sheth, co-founder of Vista who is half-Indian and whose father hails from Ambani's home state of Gujarat, the source added.
Unlike traditional mobile carriers which depend on voice services to make money, Ambani has pitched Jio as a trailblazer tech company by offering cheap mobile data plans that helped hundreds of millions of Indians use the internet for the first time.
Ambani is set to roll out a new retail venture, which combined with Jio and interests in education, music and films, could pose a challenge to established e-commerce firms such as Amazon and Walmart's Flipkart.
The investments by Facebook, and private equity firms such as Vista and Silver Lake, which primarily fund tech platforms and not telecoms carriers, will further cement Jio Platforms' position as a consumer-tech company, brokerage Axis Capital said in a note to clients.
These "deals are just a start and we expect many such marquee deals in the next 1-2 years, as this route provides much needed capital and advanced technologies," the note added.
Shares in Reliance rose 4.4% in a broader Mumbai market which was trading 1.6% higher at 0514 GMT.
Reliance last month reported a 39% decline in March quarter profit, hit by a sharp fall in oil prices and lower fuel demand.
Vista Equity has more than $57 billion in capital commitments and has invested in companies across sectors including media and entertainment, healthcare and real estate.
$1 = 75.7850 Indian rupees Reporting by Sankalp Phartiyal and Kanishka Singh; Additional reporting by Juby Babu; Editing by Lincoln Feast and Stephen Coates