Billionaire investor Carl Icahn, already a leading shareholder in Motorola, and several of his funds have filed to buy more than $2 billion, or 4.4 percent, of the company’s common stock. Motorola said yesterday it had received the required regulatory notice that Carl Icahn and Icahn Partners LP are each filing to acquire $120 million to $500 million of Motorola stock while two related entities—Icahn Partners Master Fund LP and Icahn Partners Master Fund II LP—filed to acquire in excess of $500 million but less than 25 percent of outstanding shares. The purchase would make Icahn the handset manufacturer’s second biggest institutional holder. (Via Reuters.)