(Adds background on Williams board and ETE offer, additional sourcing)
By Michael Erman and Michael Flaherty
June 30 (Reuters) - Six of Williams Cos Inc's directors, including the pipeline company's chairman, resigned on Thursday after a failed attempt to oust Chief Executive Alan Armstrong, three sources familiar with the matter told Reuters.
The resignations from the company's 13-member board come a day after Energy Transfer Equity walked away from its more than $20 billion deal to buy Williams after months of lawsuits and heated arguments between the rival pipeline companies.
Chairman Frank MacInnis, Keith Meister and Eric Mandelblatt were among the directors to step down, according to the sources. Meister and Mandelblatt run two of the company's largest investors, hedge funds Corvex Management LP and Soroban Capital Partners, respectively.
Ralph Izzo, Steven Nance and Laura Sugg also stepped down from the board, two of the sources said.
The six directors resigned after failing to get majority support to fire Armstrong. Armstrong, himself a director, had the support of the other six board members, one source said.
Williams was not available for comment.
All the directors who resigned had voted in favor of the Energy Transfer takeover last September, in an 8-5 vote. Armstrong, who is the only insider on the Williams board, was among the dissidents.
The merger of Williams and ETE, which had won regulatory approval with conditions, would have created one of the country's largest pipeline companies.
A Delaware judge ruled last week that ETE could terminate the deal after Tuesday over tax issues that were raised by the company's lawyers.
The deal has been in doubt for months, with Williams suing Energy Transfer, accusing the company of breaching their deal in trying to back out.
Williams on Wednesday said it would seek damages against Energy Transfer, believing the company had no right to end the deal. It previously said that damages could be as much as $10 billion.
SPLIT BOARD
Williams board meetings have been contentious in the past.
Corvex's Meister - a protege of Carl Icahn - and Soroban's Mandelblatt became directors in 2014 after launching an activist campaign against Williams' management in late 2013.
The company's former chairman, MacInnis, testified last week to the Delaware court that the hedge fund managers were temperamental and had "occasional outbursts" in board meetings.
MacInnis said that he had to ask Mandelblatt, a former Goldman Sachs trader, to "temper his enthusiasm, if you will, in order to avoid giving the impression of bullying."