A compound having the structure of formula I: is described. In formula I, A1, A2, A3, A4, A5, A6, A7, and A8 can be carbon or nitrogen; at least one of A1, A2, A3, A4, A5, A6, A7, and A8 being nitrogen; X is a neutral donor; is a monoanionic bidentate ligand; n is an integer from 1 to 3; ring B is bonded to ring A through a C—C bond; and ring A is bonded to the iridium through a Ir—C bond. In addition, R1, R2, R3, R4, and R6 are independently selected from hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrite, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof. Also described are formulations and devices, such as an OLEDs, that include the compound of formula I.