As he tries to hold on to his media empire, Sumner Redstone has filed for divorce from his second wife, citing "irreconcilable differences."

The split—which had been rumored even as they still appeared as a couple in public over the weekend—comes as Redstone is working to renegotiate some $1.6 billion in debt at National Amusements. The debt is backed by shares of Viacom and CBS, which have tumbled in the past year. National Amusements, a movie-theater chain in which Redstone has an 80 percent stake, is the controlling shareholder in the media companies. 

The debt talks have sparked concerns that Redstone, who is 85, may need to sell more CBS and Viacom shares, loosening his grip on those companies. Earlier this month, he sold more than $200 million worth of shares to meet a margin call.

"After five and a half years together, we have amicably ended our marriage," the couple said in a statement. "While this is a difficult decision for both of us, we remain close and supportive friends and are committed to each other's continued happiness and success. We will have no further comment and hope that you will respect our privacy."

The Los Angeles Times reports that a prenuptial agreement signed by his wife, Paula Fortunato, 46, means that she will she receive at least $5 million, or $1 million for each year of their marriage.

That payment is expected to come out of Redstone's pocket. The Hollywood Reporter says that Redstone was worth as much as $9 billion before the stock market plummeted.

Still, the divorce highlights how much is changing in Redstone's world. Yet turmoil is nothing new to the media mogul. He has famously clashed with executives and family members. He abruptly replaced Tom Freston in 2006, fired Frank Biondi, and forced out Mel Karmazin.

He is even estranged from his daughter Shari, who owns 20 percent of National Amusements and was once the heir apparent.

But business is business. The Los Angeles Times notes that Shari is leading the debt-restructuring negotiations with the banks.