The first examples of mixed halide-chalcogenide hexatungsten clusters as the molecular complexes, [W6Se8-xClx(PEt3)(6)](+), were prepared via the reaction of W6Cl12 With Na2Se and PEt3 in refluxing toluene. Single crystals of the mixed chloride-selenide cluster cationic complexes were grown from chloroform solution. The structures of two crystals from different preparations, using Na2Se and K2Se as reagents, were determined and found to have different compositions, [W6Se7.0Cl1.0(PEt3)(6)][Cl(CHCl3)(6)] and [W6Se6.4Cl1.6(PEt3)(6)][Cl(CHCl3)(6)], respectively. In the latter case the crystal contains both the 20-electron cluster [W6Se7Cl(PEt3)(6)](+) and the 21-electron cluster [W6Se6Cl2(PEt3)(6)](+) in the mole fractions 0.40 and 0.60, respectively. The two crystals were isomorphous: hexagonal, , Z = 3, a = 18.921(4) Angstrom, c = 21.275(4) Angstrom and a = 18.908(5) Angstrom, c = 21.306(5) Angstrom, respectively. The bridging chlorine and selenium atoms are disordered over all the bridging ligand sites in both structures. In the unique [Cl(CHCl3)(6)](-) anion unit, six chloroform solvent molecules are octahedrally coordinated to a chloride anion via hydrogen bonding.