A consortium including Apple Inc. and Microsoft Corp. agreed to pay $4.5 billion for a trove of patents belonging to Nortel Networks Corp., outbidding Google Inc. and others in what is believed to be largest intellectual-property auction of all time.

The price offered by the six-company group—five times Google's opening bid—shows the rising value of patents in the increasingly competitive and litigious wireless business. It also underscores the determination of companies including Apple, Microsoft and Research In Motion Ltd....