Yahoo! (YHOO) was down 4.7% in preopen Island trading after naming Terry Semel as its chairman and CEO, effiective May 1.

Semel previously was at

AOL Time Warner's

(AOL)

TheStreet Recommends

Warner Bros.

unit, where he served at co-chairman and co-CEO.

He replaces Tim Koogle, who stepped down as CEO of Yahoo! on March 7. Koogle will remain as vice chairman of the Internet media company until August and will retain a seat on the board.

Yahoo! said Semel bought 1 million of its shares.