* TSX down 233.47 pts, or 2 pct, at 11,627.19 * Touches lowest level since Dec. 20, 2011 * Materials fall 3.5 pct, financials down 1.6 pct * Greek uncertainty hurts sentiment By Jon Cook TORONTO, May 8 (Reuters) - Toronto's main stock index was on track for its biggest one-day plunge in six months on Tuesday, with mining and energy shares selling off on concerns about Greece's commitment to bailout pledges that threatened to escalate the euro zone's debt crisis. The results of weekend polls in Greece and France, in which voters soundly rejected austerity measures, heightened the uncertainty of the path ahead for the euro zone. Greece sank even deeper into crisis on Tuesday when a centrist conservative party said leftist candidate for prime minister, Alexis Tsipras, would drive the country out of the euro with his proposal to reject an international bailout. The Greek drama unfolding may have implications for other struggling euro zone nations such as Spain, which could follow suit in rejecting harsh austerity constraints, said Gavin Graham, president at Graham Investment Strategy. "If Spain chooses to renegotiate its bonds and make foreign bond owners eat a 75-percent haircut, which is what happened in Greece, then effectively the French and German banking systems are going to be under severe stress," said Graham. Canadian financial firms, which have less exposure to risky European debt holdings than their global counterparts, were down 1.6 percent. Losses were led by major lenders Royal Bank of Canada, down 2.1 percent at C$53.87, Toronto-Dominion Bank, off 1.8 percent at C$80.21, and Bank of Nova Scotia, which dipped 1.7 percent to C$52.67. Canadian stocks were on track for their fifth straight drop as the heavyweight materials group tumbled 3.5 percent as miners were hit by a sharp drop in gold and base metals prices. Losses were led by top gold producers Barrick Gold and Goldcorp Inc. Barrick, the world's largest gold miner, fell 2.7 percent to C$36.64 and Goldcorp sank 3.8 percent to C$34.55. "With the decline in prices you're starting to get that cleansing process where the baby gets thrown out with the bath water," said Arthur Salzer, executive director and chief executive officer of Northland Wealth Management. Base metals miners fell 4 percent, led by Teck Resources , down 4.5 percent to C$32.78, and First Quantum Minerals, off 4 percent to C$17.40. At 1:35 EDT (1735 GMT), the Toronto Stock Exchange's S&P/TSX composite index was down 233.47 points, or 2 percent, at 11,627.19, on track for its biggest single-day drop since Nov. 17. The TSX has fallen nearly 6 percent since the beginning of May. Energy shares were down again on Tuesday, slipping 2.3 percent as Brent crude oil dipped below $112 a barrel, down more than 6 percent so far this month. Suncor Energy, Canada's largest oil producer, dropped 2.3 percent to C$29.51 to lead the influential sector's losses. Canadian Natural Resources was down 3.8 percent at C$30.43 and Encana Corp fell 2.3 percent to C$20.87. In other company news, shares of Research In Motion Ltd rose 1.1 percent to C$11.88 after the struggling BlackBerry maker named chief marketing and operating officers on Tuesday ahead of the launch of its next-generation BlackBerry 10 smartphones later this year. Canadian Pacific Railway stock fell 1.5 percent to C$73.40 after the head of U.S. hedge fund Pershing Square Capital Management said on Tuesday that the future of Canada's second-biggest railway should be decided by shareholder vote.