Dicyclohexylphosphine, HPcycl 2, reacts with mercury(II) and cadmium(II) halides to give isolable 1:1 adducts HgX 2(HPcycl 2) (X = Cl, Br, I), CdX 2(HPcycl 2) (X = Br, I) and 1:2 adducts HgX 2(HP-cycl 2) 2, CdX 2(HPcycl) 2 (X = Cl, Br, I). The 1:2 adducts HgX 2(HPcycl 2) 2 react in solution with additional HPcycl 2 to give 1:3 adducts HgX 2(HP-cycl 2) 3 whereas the corresponding CdX 2(HPcycl 2) 2 do not react further with HPcycl 2.Both mercury(II) and cadmium(II) 1:1 adducts react with halide ion to give anionic [MX 3HPcycl 2] − (M = Hg, Cd) species in solution. The ligand (1-(dicyclohexylphosphino))-N-phenylthioformamide, LH, (LH = (C 6H 11) 2PC(S)N(H)C 6H 5) reacts with mercury(II) halides to give isolable 1:1 and 1:2 adducts, [HgX 2(LH)] 2 and HgX 2(LH) 2, in which coordination of the ligand occurs only through the phosphorus atom. There is no evidence for the addition of a third LH to mercury but the 1:1 adducts react with halide ion to give anionic [HgX 3LH] − species. The 1:2 adducts HgX 2(HPcycl 2) 2 and CdX 2(HPcycl 2) 2 react in solution with C 6H 5NCS to form the corresponding MX 2(LH) 2 complexes. NMR data imply formation in solution of dimeric [CdX 2(LH)] 2 compounds in which LH acts as a bridging ligand bonding through sulphur and phosphorus. Mixed ligand species HgX 2(HPcycl 2)(LH) and CdX 2(HPcycl 2)(LH) are also identified in solution. Phosphorus-31, cadmium-113 and mercury-199 NMR spectra were used to characterise new species in solution. There is no evidence for phosphido formation in any of the systems investigated in this study.