Five compounds have been reported: Mo₂B , melting point, 2,120 degrees C, and sp gr, 9.3; Mo₃B₂, dissociates at 2,250 degrees C; MoB, exists in two crystalline forms: alpha MoB, melting point, 2,350 degrees C, sp gr, 8.8; and beta MoB, melting point, 2,180 degrees C, sp gr, 8.4; Mo₂B₅, dissociates at approx. 1,600 degrees C, sp gr, 7.5; and MoB₂, melting point, 2,100 degrees C, sp gr, 7.8, and thermal expansion, 7.7 x 10_-6.