Here are some key developments in Google's Inc.'s planned acquisition of Motorola Mobility Holdings Inc.:

Aug. 15, 2011: Google announces plans to spend $12.5 billion to buy Motorola Mobility. Google would get Motorola's lineup of cellphones, tablet computers and cable set-top boxes. More important, Google would get Motorola's more than 17,000 patents — a crucial weapon in an intellectual arms race with Apple, Microsoft and others to gain more control over the increasingly lucrative market for mobile devices.

Aug. 16: Standard & Poor's says investors should sell Google's stock because it believes the decision to buy Motorola Mobility increases the risk to the company and its shares. S&P says that although the acquisition would include a patent trove, that might not be enough to keep Google's Android mobile operating software from encountering intellectual-property issues.

Aug. 22: Standard & Poor's reverses course, saying Google shares have fallen so much they've now become a good deal.

Sept. 13: In a regulatory filing, Google reveals that the $12.5 billion purchase price is 33 percent more than Google initially offered. If the deal falls through, Google will still have to pay Motorola Mobility $2.5 billion.

Sept. 28: It's disclosed that the U.S. Justice Department is taking a closer look at the deal. The move had been widely expected.

Oct. 27: Motorola Mobility reports smaller net loss in the July-September quarter as phone shipments rises by more than 25 percent from a year earlier.

Nov. 17: Motorola Mobility says its shareholders have overwhelmingly voted to accept the proposed sale.

Dec. 2: With the Motorola deal still pending, the U.S. Justice Department approves Google's acquisition of online advertising service Admeld after concluding the deal wouldn't diminish competition in one of the Internet's most lucrative marketing niches.

Jan. 26, 2012: Motorola Mobility issues disappointing results for the last three months of the year. It reports a loss, mirroring preliminary numbers issued three weeks earlier, amid fierce competition in the markets for smartphones and tablet computers. Some analysts have already been worried that Motorola Mobility will become a financial millstone that could drag down Google's earnings growth. If that happens, Google's stock price would likely suffer.

Feb. 13: European antitrust regulators clear the deal. Although regulators say they didn't find a reason to believe that the transaction would pose any competitive problems, they raise concerns about Motorola's aggressive enforcement of its patents. Hours later, the U.S. Department of Justice also approves the deal.

Wednesday: Microsoft lodges a formal complaint with the European Union's competition regulator accusing Motorola Mobility of breaking competition rules with its aggressive enforcement of patent rights against rivals. The complaint also names Google, which Microsoft fears will continue Motorola Mobility's tight hold on key patents. It follows a similar complaint from Apple.