Na2PdC2 and Na2PtC2 are the first examples of ternary alkali metal transition metal acetylides. They were synthesized and structurally characterised by our group in 2001 based on neutron diffraction experiments. The C-C bond length is approx. 6 pm longer than the expected distance for a C-C triple bond. This can be explained by a backbonding from palladium/platinum into the antibonding states of the C2 units. Pure Na2PdC2 is red and a semiconductor with a very small indirect band gap. Pure K2PdC2 and Rb2PdC2 are yellow. Measurements of the diffuse reflectivity show that the direct band gap is shifted from 594 nm (Na2PdC2) to 486 nm (K2PdC2) and 448 nm (Rb2PdC2). We would like to perform neutron diffraction experiments on K2PdC2, K2PtC2 and Rb2PdC2 to be able to compare the structural data with the results of the spectroscopic measurements to understand how they are related to each other.