A duplex at elite 740 Park Ave. seeks a buyer

Once the residence of John D. Rockefeller Jr.,the 31-unit, limestone, prewar co-op today is home to executives including David Koch, Israel Englander and Steven Schwarzman.

But even high society can butt heads. In 2016 Tang and his wife, Miranda, sued their upstairs neighbor, billionaire Howard Marks, over his long-running renovation. Its “heavy machinery, banging, crashing, hammering and drilling” was damaging their unit and causing “sleep deprivation,” according to the complaint at the time.

Also accusing 740’s co-op board in the suit, the Tangs said that the board had bent its renovation rules to favor the deep-pocketed Marks, the co-founder of investment firm Oaktree Capital Management who had paid the princely sum of $52.5 million for his duplex.

The old rules stipulated that renovations could happen only after 9 a.m. and last two years at the most, but Marks, whose renovation began in 2012 and went on for years, was allowed to start earlier in the morning.

Ultimately, the sides settled. The co-op restored the stricter work hours and also repaired cracks inside the Tangs’ apartment, according to lawyers in the case. Marks’ apartment, No. 12/13, was thoroughly soundproofed, said Adam Leitman Bailey, an attorney for the Tangs.

“You can’t hear someone with high heels walking on the floor. You couldn’t hear weights if they were dropped on the floor. And the damage has fully been fixed,” Leitman Bailey said. “They couldn’t have done a better job.”

A message left for Matthew Cuomo, a defense attorney representing Marks, was not returned. Francine Crocker, the Corcoran Group agent with the listing, declined to comment.

Still, whether the Tangs can easily unload their home, which comes with a monthly maintenance fee of $21,772, may be up in the air.

John Thain, a former chief executive of CIT Group, has been unable to sell his duplex penthouse for four years, and if it were to get its current list price of $27.5 million, it would trade at a slight loss, records show.

Hamburg Tang, who emigrated from China, was a founder of Alloys Unlimited, a Long Island City-based semiconductor manufacturer. In 2013, records show, the Tangs folded their apartment into a trust named for their son, Hamburg Tang Jr., a managing director of the investment firm GIA Partners.