A compound of Formula I is disclosed. In the structure of Formula I, ring A and ring B are 5- or 6-membered rings; L1, L2, L3, and Z are each linking groups; a, b, and c are each 0 or 1, and a+b+c=2 or 3; K1, K2, K3, and K4 are each a direct bond, O, or S; Z1 to Z6 and X1 to X5 are each C or N; W is a linking group comprising 3 to 5 linking atoms, which can be further substituted; M is Pd or Pt; each RA, RB, RC, RD, RE, R, and R′ is selected from H or a variety of substituents, and can be joined to another substituent for form a ring. Organic light emitting devices, consumer products, formulations, and chemical structures containing the compounds are also disclosed.