Yale University has agreed to buy the 136-acre Bayer HealthCare complex in a deal that represents its largest land expansion and will help accelerate research into cures for diseases, officials said Wednesday.

Yale will acquire 550,000 square feet of lab research space on the site, which Bayer (BAY) decided last year to sell as part of a reorganization. Bayer's science labs will help Yale attract top scientists and undertake research programs that the university would not have had the space to develop for a decade or more, officials said.

"It's an exciting opportunity for Yale to accelerate its progress in the sciences and medicine," Yale President Richard C. Levin said in an interview. "We want our university to be among the very best in the world in advancing scientific knowledge and we see great potential with this expanded space for contributing to humanity's struggle against disease."

The purchase is also one of the largest expansions by a major university in recent years, Yale officials said.

Yale has not decided exactly how it will use the site, but Levin mentioned research into cancer, Alzheimer's and cardiovascular diseases as potential areas of focus.

Yale scientists and researchers in recent years have made progress in a variety of areas, ranging from discoveries that led to new approaches for combating malaria to creating tissue-engineered heart valves. Many of the 40 biotech companies in the New Haven area are the result of Yale research.

Officials said they would not disclose the purchase price until the deal is closed, but people familiar with the deal say the site was bought for about $100 million.

"It's economically very attractive for the university," Levin said.

The state had offered Bayer a $60 million incentive package to keep the West Haven site open and add jobs. Officials then tried unsuccessfully to lure other companies.

"While Bayer is sad to be leaving the site in West Haven and Orange, we are thrilled to be transferring our legacy of innovation to a renowned research institution with which we share a long standing collaborative relationship," said Gunnar Riemann, member of the Board of Management and president of Pharmaceuticals, Bayer HealthCare AG.

Yale, which is exempt from municipal taxes, will make voluntary payments starting at about $600,000 annually that will be shared between West Haven and Orange, officials said. The two municipalities also will receive state funds in lieu of taxes that amount to about 70 percent of the $2.2 million in property taxes paid by Bayer, which was West Haven's biggest taxpayer and once employed thousands on the site.

Yale also plans to invest $1 million over the next four years in local schools.

"I'm ecstatic," said West Haven Mayor John Picard. "I think it's the single greatest thing that will happen to West Haven for generations to come."

Picard said the agreement will bring back thousands of employees to the site and put West Haven on the map as a center for Yale research. Yale research has led to numerous biotech spinoff companies in recent years, but Levin said those would continue to be housed in New Haven.

Levin said he expected several hundred employees in the short term. Noting that vast size of the property, he said the site could eventually have more than the 2,500 employees Bayer had at its peak.

"It's an once in a century opportunity," he said at a news conference announcing the deal.

Gov. M. Jodi Rell, who addressed the news conference by phone, also welcomed the deal.

"We know the innovation is the key to our state's economic future," Rell said.

Yale officials emphasized that the university remains committed to New Haven. Levin said Yale plans to build more than 2 million square feet of new facilities there over the next six years.

Kelly Murphy, New Haven's economic development administrator, said the city was not concerned that Yale was expanding into West Haven.

"At the end of the day the university is still here," Murphy said.