Two polymorphs of [Rh(μ-I)(COD)]2.

The solid-state structure of di-μ-iodido-bis-{[(1,2,5,6-η)-cyclo-octa-1,4-diene]rhodium(I)}, [Rh2I2(C8H12)2] or [Rh(μ-I)(COD)]2, was determined from two crystals with different morphologies, which were found to correspond to two polymorphs containing Rh dimers with significantly different mol-ecular structures. Both polymorphs are monoclinic and the [Rh(μ-I)(COD)]2 mol-ecules in each case possess C2 v symmetry. However, the core geometry of the butterfly-shaped Rh2I2 core differs substanti-ally. In the C2/c polymorph, the core geometry of [Rh(μ-I)(COD)]2 B is bent, with a hinge angle of 96.13 (8)° and a Rh⋯Rh distance of 2.9612 (11) Å. The P21/c polymorph features a more planar [Rh(μ-I)(COD)]2 P core geometry, with a hinge angle of 145.69 (9)° and a Rh⋯Rh distance of 3.7646 (5) Å.