Amazon.com Incorporated announced Friday it will spend more than $1 billion to buy its corporate headquarters in Seattle from the investment firm of Microsoft Corporation co-founder Paul Allen. The world’s biggest internet retailer plans to buy 11 buildings for $1.16 billion. The company said it expects to close the deal in the fourth quarter of this year. Amazon had been leasing the space, but at the end of August, Allen’s Vulcan Real Estate put the buildings in Seattle’s South Lake Union area up for sale.