Three clusters 1-3, Cu-8(mu8-Cl)[Se2P(OR)(2)](6)(PF6) (R= Et, Pr, 'Pr), were synthesized in high yield from the reaction of [Cu(CH3CN)(4)](PF6), NH4[Se2P(OR)(2)], and Bu4NCl in a molar ratio of 4:3:1 in diethyl ether. FAB mass spectra show m/z peaks at 2218.10 for 1, 2386.10 for 2, and 2387.34 for 3 which are due to molecular cations, [1-PF6](+), [2-PF6](+), and [3-PF6](+), respectively. P-31 NMR spectra of 1-3 display a singlet at delta 76.48, 76.73, and 69.32 ppm with satellites (J(PSe) = 652, 653, and 648 Hz), respectively. The Se-77 NMR spectra of 1-3 exhibit a doublet peak at -21.7, -16.42, and 2.3 ppm, respectively (J(SeP) = 652 Hz for 1, 653 Hz for 2, and 648 Hz for 3). The X-ray structure (1-3) consists of a discrete cationic cluster in which eight copper ions are linked by six diselenophosphate ligands and a central mu(8)-Cl ion with a noncoordinating PF6- anion. The shape of the molecule is a chloride-centered distorted Cu-8 cube in clusters 1 and 2 and a near perfect Cu-8 cube for cluster 3. The dsep ligand exhibits a tetrametallic tetraconnective (mu(2), mu(2)) Coordination pattern, and each occupies a square face of the cube. Each copper atom of the cube is coordinated by three selenium atoms with a strong interaction with the central chloride ion. The observed Cu-Cl distances lie in the range 2.649-2.878 Angstrom.