IrAs2 crystallizes in the monoclinic P2_1/c space group. Ir(1) is bonded to three equivalent As(1) and three equivalent As(2) atoms to form distorted IrAs6 octahedra that share corners with eight equivalent Ir(1)As6 octahedra, corners with three equivalent As(1)AsIr3 tetrahedra, corners with three equivalent As(2)AsIr3 tetrahedra, and edges with two equivalent Ir(1)As6 octahedra. The corner-sharing octahedral tilt angles range from 54-60°. There are two inequivalent As sites. In the first As site, As(1) is bonded to three equivalent Ir(1) and one As(2) atom to form AsAsIr3 tetrahedra that share corners with three equivalent Ir(1)As6 octahedra, corners with four equivalent As(1)AsIr3 tetrahedra, corners with nine equivalent As(2)AsIr3 tetrahedra, and  an edgeedge with one As(1)AsIr3 tetrahedra. The corner-sharing octahedral tilt angles range from 68-73°. In the second As site, As(2) is bonded to three equivalent Ir(1) and one As(1) atom to form AsAsIr3 tetrahedra that share corners with three equivalent Ir(1)As6 octahedra, corners with four equivalent As(2)AsIr3 tetrahedra, corners with nine equivalent As(1)AsIr3 tetrahedra, and  an edgeedge with one As(2)AsIr3 tetrahedra. The corner-sharing octahedral tilt angles range from 73-78°.
IrAs2 crystallizes in the monoclinic P2_1/c space group. Ir(1) is bonded to three equivalent As(1) and three equivalent As(2) atoms to form distorted IrAs6 octahedra that share corners with eight equivalent Ir(1)As6 octahedra, corners with three equivalent As(1)AsIr3 tetrahedra, corners with three equivalent As(2)AsIr3 tetrahedra, and edges with two equivalent Ir(1)As6 octahedra. The corner-sharing octahedral tilt angles range from 54-60°. There is one shorter (2.51 Å) and two longer (2.52 Å) Ir(1)-As(1) bond lengths. There are two shorter (2.43 Å) and one longer (2.45 Å) Ir(1)-As(2) bond length. There are two inequivalent As sites. In the first As site, As(1) is bonded to three equivalent Ir(1) and one As(2) atom to form AsAsIr3 tetrahedra that share corners with three equivalent Ir(1)As6 octahedra, corners with four equivalent As(1)AsIr3 tetrahedra, corners with nine equivalent As(2)AsIr3 tetrahedra, and  an edgeedge with one As(1)AsIr3 tetrahedra. The corner-sharing octahedral tilt angles range from 68-73°. The As(1)-As(2) bond length is 2.47 Å. In the second As site, As(2) is bonded to three equivalent Ir(1) and one As(1) atom to form AsAsIr3 tetrahedra that share corners with three equivalent Ir(1)As6 octahedra, corners with four equivalent As(2)AsIr3 tetrahedra, corners with nine equivalent As(1)AsIr3 tetrahedra, and  an edgeedge with one As(2)AsIr3 tetrahedra. The corner-sharing octahedral tilt angles range from 73-78°.