Greece's failure to finalize a deal with creditors sent the markets down during the midday with the Dow tumbling 82 points to 12,577. Nasdaq lost 13 points to 2803.

On the upside

A Seeking Alpha contributor wrote that Arena Pharmaceuticals (Nasdaq: ARNA) has an upside potential of 300% in 2012.

Shares of Chinese social networking site Renren (NYSE: RENN) surged over reports that Facebook may file for for its initial public offering this Wednesday.

The Wall Street Journal reported that Delta Air Lines (NYSE: DAL) may be exploring the possible acquisition of US Airways (NYSE: LCC).

On the downside

The Federal Trade Commission sued to block Omnicare's (NYSE: OCR) $440.8 million acquisition of PharMerica (NYSE: PMC).

Emcore (Nasdaq: EMKR) announced a one for four reverse stock split.

TheStreet upgraded YPF Sociedad Anonima (NYSE: YPF) to a Buy rating but the stock price fell.

In the broad market, declining issues outpaced advancers by a margin of nearly 3 to 1 on the NYSE and by nearly 5 to 2 on Nasdaq. The Russell 2000 which tracks small cap stocks fell 7 points to 791.