Organic electroluminescent materials and devices

A compound comprising a first ligand LA of Formula I;

• wherein X1-X6 are each independently C or N;
• wherein Y is selected from the group consisting of BR, BRR′, NR, PR, O, S, Se, C═R″, CRR′, SiRR′, and GeRR′;
• wherein K1 represents a direct bond, O, or S;
• wherein any two substituents may be joined or fused together to form a ring;
• wherein at least two adjacent RB substituents are joined or fused together to form a 5-membered or 6-membered carbocyclic or heterocyclic ring;
• wherein RA and RB each independently represent mono to the maximum allowable substitution, or no substitution;
• wherein each R, R′, RA and RB is independently hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, boryl, arylalkyl, alkoxy, aryloxy, amino, silyl, germyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, selenyl, and combinations thereof;
• wherein R″ is independently selected from the group consisting of O, S, NR and CRR′;
• wherein LA is coordinated to a metal M;
• wherein M is selected from the group consisting of Os, Ir, Pd, Pt, Cu, Ag, and Au;
• wherein M may be coordinated to other ligands;
• wherein LA may be joined with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand;
• and
• wherein the compound is not: