The present invention relates to organic electroluminescent devices comprising metal complexes of the formula (1), and to metal complexes for use in organic electroluminescent devices. Depending on the metal used, the metal complexes are useful as emitters, as matrix materials, as hole-blocking materials, as electron-transport materials, and in other functions in the OLED. Organic electroluminescent devices comprising the metal chelate complexes described herein result in significant improvements in the organic electroluminescent device, in particular with respect to the lifetime, the efficiency and the stability to heating, particularly in green- and blue-phosphorescent electroluminescent devices.