LONDON--WPP PLC (WPP.LN), a communications services group, and Press Index S.A. (ALPRI.FR), a media intelligence and monitoring group, announced Thursday exclusive negotiations for the acquisition by WPP of shares representing 8% of the outstanding shares of Press Index from its founders as well as other sellers. MAIN FACTS: -Provided this transaction completes, the purchaser would initiate an all-cash simplified tender offer to acquire the remaining outstanding shares of Press Index -The price per share would be 6.81 euros in cash; this price would currently value Press Index at EUR11.2 million total equity value. -WPP shares at 902 GMT, down 14 pence, or 1.79%, at 739.5 pence valuing the company at GBP9.49 billion. -Write to Rory Gallivan at rory.gallivan@dowjones.com