Three disgruntled shareholders in a New York-listed lithium miner being sold to Rio Tinto have sued the US company and its board, accusing them of negligently leaving money on the table in the $US6.7 billion ($9.9 billion) deal.

The lawsuits – filed in four separate US courts – allege Arcadium Lithium’s directors misled shareholders and failed in their fiduciary duty to maximise value, according to market filings.