Donald B. Marron, a prominent Wall Street financier and philanthropist and a major figure in the New York art world, died on Friday in Manhattan. He was 85.

Catherine Marron, his wife, confirmed the death. She said he had been en route to a colleague’s holiday cocktail party and was getting out of a car when he had what appeared to be a heart attack. He lived on the Upper East Side of Manhattan.

Mr. Marron’s influence ranged across the disparate worlds of high finance, art and government policy. He led some of Wall Street’s most powerful firms, played a shaping role in the expansion of the Museum of Modern Art in New York and delved into policy issues as a member of the Council on Foreign Relations and other organizations.

Early in his career, as president and chief executive, Mr. Marron oversaw the transformation of Mitchell Hutchins from a predominantly retail-oriented outfit into one of Wall Street’s premier stock research firms. He sold it to PaineWebber, the investment bank and stock brokerage firm, in 1977.