Paramagnetic, chalcogenido–M(V) dithiolene complexes, [Tp*ME{S₂C₂(CO₂Me)₂}] [M = Mo, E = O (1), S (2); M = W, E = O (3), S (4); Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate] are generated in the reactions of dimethyl acetylenedicarboxylate (DMAC) and the sulfur-rich complexes NEt₄[Tp*MoS(S₄)] and NEt₄[Tp*WS₃]; the oxo complexes result from hydrolysis of the initial sulfido products. As well, a novel ‘organoscorpionate’ complex, [W{S₂C₂(CO₂Me)₂}{SC₂(CO₂Me)₂–Tp*}] (5), has been isolated from the reactions of NEt₄[Tp*WS₃] with excess DMAC. Complexes 1, 4 and 5 have been isolated and characterised by microanalytical, mass spectrometric, spectroscopic and (for 4 and 5) X-ray crystallographic techniques. Complexes 2 and 3 have been partially characterised by mass spectrometry and IR and EPR spectroscopy. Six-coordinate, distorted-octahedral 4 contains a terminal sulfido ligand (WS = 2.108(3) Å), a bidentate dithiolene ligand (S–C_av = 1.758 Å, CC = 1.332(10) Å) and a fac-tridentate Tp* ligand. Seven-coordinate 5 contains a planar, bidentate dithiolene ligand (S–C_av = 1.746 Å, CC = 1.359(5) Å) and a novel pentadentate ‘organoscorpionate’ ligand formed by the melding of DMAC, sulfido and trispyrazolylborate units. The latter is coordinated through two pyrazolyl N atoms (κ²-N,N′) and a tridentate κ³-S,C,C′ unit appended to N-β of the third (uncoordinated) pyrazolyl group. The second-generation [Tp*ME(dithiolene)] complexes represent a refinement on first-generation [Tp*ME(arene-1,2-dithiolate)] complexes and their synthesis affords an opportunity to compare and contrast the electronic structures of true vs. pseudo-dithiolene ligands in otherwise analogous complexes.