SAN FRANCISCO, CA — Investor Carl Icahn on Monday filed the final paperwork to nominate a hand-picked slate of members for Yahoo’s board of directors, escalating his takeover plans for the company as part of a bid to force Yahoo’s sale to Microsoft. Icahn’s name is among the nominees.Elections are scheduled for August 1st, and the entire nine-member board is subject to ouster. At issue, according to Icahn, is the incumbent board’s continuing refusal to entertain Microsoft’s serial offers to buy part or all of the world’s second-largest search-engine company. Icahn, who owns 5-percent of Yahoo’s stock, has said he believes board members are neglecting their fiduciary duty to stockholders in favor of retaining their own jobs.

Icahn also has communicated directly with other shareholders in order to explain his position and his vision for Yahoo’s future. In a recent letter to stockholders, he wrote, “Our company is on a precipice and our board seems ready to take the risk of seeing it topple.”

Yahoo Chairman Roy Bostock and Chief Executive Officer Jerry Yang responded with their own letter to shareholders, saying “We are prepared to let you, our stockholders, not Microsoft and Carl Icahn, decide what is in your best interests and we look forward to the upcoming vote.” The letter also called Microsoft’s offers “ludicrous.”

Yang also has been communicating with employees, warning them turbulent waters may lie ahead as Icahn and Microsoft redouble their efforts to gain control of the company.

“The last few months and weeks have certainly been challenging, and the waters are not likely to calm before our stockholder meeting,” he wrote in a letter to Yahoo employees.

Although he has a history of corporate takeovers that worked out well, Icahn is seen by some as a risky bet to lead Yahoo into the future. He has no experience in the internet industry, and as yet he has been unable to guarantee Microsoft would reopen negotiations if he takes over the board. In addition, there has been speculation that Microsoft might lower its bid for the company from the $33 per share Yahoo rejected outright in May to $30 per share.

Yang, who also would be ousted under Icahn’s plan, has said he believes Yahoo stands to be more profitable under a proposed deal with Google that currently is undergoing antitrust scrutiny. Under that deal, Yang said Yahoo would increase its operating capital from $250 to $450 million per year. Under the Microsoft plan, the company would realize only $300 million annually, he said.

The wrangling is playing havoc with Yahoo stock. After a 10-percent rise last week on news that Microsoft might be willing to reopen acquisition negotiations if the incumbent board was ousted, Yahoo stock plunged 4.2-percent on Monday.