UPDATE 1-PNC to buy $506 mln in BlackRock stock

* PNC to buy 3.6 mln preferred shares for $140.60/shr

* BlackRock to sell 16.4 mln common shares at $140.60/shr

* PNC off 3.6 pct, BlackRock down 1.3 pct

NEW YORK, June 17 (Reuters) - PNC Financial Services Group Inc (PNC.N) agreed to buy about $506 million worth of BlackRock Inc's (BLK.N) preferred shares to help fund the money manager's $13.5 billion purchase of a Barclays PLC (BARC.L) unit, according to a filing on Wednesday.

PNC, which is a major BlackRock shareholder, agreed to purchase about 3.6 million of BlackRock's preferred shares at a price of $140.60 per share, according to a U.S. Securities and Exchange Commission filing.

BlackRock also plans to sell about 16.4 million common shares at $140.60 per share. It expects to receive a total of $2.8 billion from the sale of the preferred and common shares.

The move is part of BlackRock's acquisition of Barclays Global Investors from the British lender. [ID:nN16132352]

PNC's shares closed down 3.6 percent, or $1.40, at $37.99, while BlackRock was off 1.3 percent, or $2.20, at $167.25, both on the New York Stock Exchange. (Reporting by Paritosh Bansal; Editing Bernard Orr) (For more M&A news and our DealZone blog, go to www.reuters.com/deals)