The fight among powerhouse dealers to represent lucrative artists’ estates is never-ending. This week the Pace Gallery said it had won the rights to the estate of Willem de Kooning. The Abstract Expressionist painter, who died in 1997, had previously been handled by the Gagosian Gallery. Officials at Pace said they were planning to hold a major drawing exhibition next year. “We have had a long relationship with de Kooning,’’ Arne Glimcher, the gallery’s chairman, said in a telephone interview. “I knew him personally, and after he died the gallery was the first to sell paintings for the estate.’’ Over the years Pace has also organized several exhibitions including “de Kooning/Dubuffet: The Women,” in 1991. The news could be seen as something of a payback. In May, the Gagosian Gallery said it had been selected to represent the estate of Robert Rauschenberg, who died in 2008. His work had been handled by Pace for more than 15 years.