For compounds with the formula MX, the chief alternative to octahedral geometry is a trigonal prismatic geometry, which has symmetry D. In this geometry, the six ligands are also equivalent. There are also distorted trigonal prisms, with C symmetry; a prominent example is . The interconversion of Δ- and Λ-complexes, which is usually slow, is proposed to proceed via a trigonal prismatic intermediate, a process called the "Bailar twist". An alternative pathway for the racemization of these same complexes is the Ray–Dutt twist.