Monomeric, five-coordinate bis(diethyldithiocarbamato)M(II)(trialkylphosphine) complexes, 1 (M = Zn, alkyl = Me), 2 (M = Zn, alkyl = Et), 3 (M = Cd, alkyl = Me), and 4 (M = Cd, alkyl = Et) have been synthesized by addition of trialkylphosphine ligands to toluene solutions of bis(diethyldithiocarbamato)M(II) (M = Zn, and Cd). The bidentate ligand, 1,2-bis(diethylphosphino)ethane (DEPE) reacted with bis(diethyldithiocarbamato)M(II) (M = Zn, Cd) and a 1:1 mixture of [(Et 2NCS 2) 2Zn] 2: [(Et 2NCS 2) 2Cd] 2 in toluene to form five-coordinate, dinuclear DEPE-bridged complexes, [(Et 2NCS 2M] 2(μ-DEPE), 5 (M = Zn), 6 (M = Cd) and 7 [(Et 2NCS 2) 2Zn](μ-Et 2PCH 2CH 2PEt 2)[Cd(Et 2NCS 2) 2], respectively. The composition and structure of all compounds was confirmed by elemental analyses, infra-red spectroscopy, 1H, 13C{ 1H} and 31P{ 1H} nuclear magnetic resonance (NMR) spectroscopy and in selected cases by X-ray crystallography. Variable temperature 31P{ 1H} and 113Cd{ 1H} NMR showed that these complexes undergo a dynamic exchange process at room temperature involving MP bond cleavage with activation parameters of Δ H‡ = 9 kcal mol −1 and Δ S° = −7 eu as determined by two independent measurements based on simulation of variable temperature 31P{ 1H} and 113Cd{ 1H} NMR data for 4. The solid-state structures of (Et 2NCS 2) 2ZnPMe 3 ( 1) and (Et 2NCS 2)CdPEt 3 ( 4) have been determined by single-crystal X-ray diffraction. The single crystal X-ray diffraction structure of [(Et 2NCS 2) 2Zn] 2(μ-DEPE) · 2C 7H 8 ( 5) has been reported earlier and confirmed the dinuclear nature showing that the two zinc units were bridged by the DEPE ligand and not chelated. Thermogravimetric analysis (TGA) of compounds 1–3 showed that the PR 3 ligands dissociated prior to thermal decomposition. However, compound 4 exhibited a single weight loss to give crystalline CdS as determined by X-ray powder diffraction, electron diffraction and transmission electron microscopy. The homobimetallic species, 5 and 6, also decomposed to give ZnS and CdS, respectively while the heterobimetallic species, 7, thermally decomposed to give crystalline Zn 0.5Cd 0.5S according to X-ray powder diffraction data.