The compounds Pd(PPh3)4, Pt(PPh3)4 and Pt(PPr3i)2 react with CS2, CSSe and CSe2 to give the mononuclear complexes (PR3)2M(η2-CEE′). From Pd(PPh3)4 and excess CSe2 the compound (PPh3)2PdC2Se4 is obtained. 1,2-C2H4(PPh2)2 (diphos) and 1,2-C6H4(CH2PPh2)2 (dpmb) react with (PR3)2M(η2-CEE′) by ligand displacement to produce the chelate complexes (diphos)M(η2-CEE′) and (dpmb)M(η2-CEE′), respectively. The reaction of (PPh3)2Pt(η2-COS) with diphos leads to the formation of the carbonyl compound (diphos)Pt(CO). In solution, the complexes (diphos)M(η2-CS2) and (diphos)M(η2-CSe2) slowly dimerise to form products of composition [(diphos)M(CEE′)]2 which probably contain bridging CS2 and CSe2 units. (PPh3)2Pd(η2-CSe2) reacts with PMe3, PMe2Ph and PMePh2 to produce the binuclear compounds [(PR3)Pd(Se2CPR3)]2 in which the zwitterionic ligand PR3CSe2 bridges the two Pd(PR3) fragments. The analogous complexes [(PR3)Pd(SSeCPR3)]2 are prepared from Pd(PR3)4 (PR3 = PMe3, PMe2Ph, PMePh2) and CSSe.